@article{ShainyanSuslovaTranDinhPhienetal.2019, author = {Shainyan, Bagrat A. and Suslova, Elena N. and Tran Dinh Phien, and Shlykov, Sergey A. and Heydenreich, Matthias and Kleinpeter, Erich}, title = {1-Methylthio-1-phenyl-1-silacyclohexane: Synthesis, conformational preferences in gas and solution by GED, NMR and theoretical calculations}, series = {Tetrahedron}, volume = {75}, journal = {Tetrahedron}, number = {46}, publisher = {Elsevier}, address = {Oxford}, issn = {0040-4020}, doi = {10.1016/j.tet.2019.130677}, pages = {9}, year = {2019}, abstract = {1-Methylthio-1-phenyl-1-silacyclohexane 1, the first silacyclohexane with the sulfur atom at silicon, was synthesized and its molecular structure and conformational preferences studied by gas-phase electron diffraction (GED) and low temperature C-13 and Si-29 NMR spectroscopy (LT NMR). Quantum-chemical calculations were carried out both for the isolated species and solvate complexes in gas and in polar medium. The predominance of the 1-MeSaxPheq conformer in gas phase (1-Ph-eq :1-Ph-ax = 55:45, Delta G degrees = 0.13 kcal/mol) determined from GED is consistent with that measured in the freon solution by LT NMR (1-Ph-eq:1-Ph-ax = 65:35, Delta G degrees = 0.12 kcal/mol), the experimentally measured ratios being close to that estimated by quantum chemical calculations at both the DFT and MP2 levels of theory. (C) 2019 Elsevier Ltd. All rights reserved.}, language = {en} } @article{BouaklineFischerSaalfrank2019, author = {Bouakline, Foudhil and Fischer, E. W. and Saalfrank, Peter}, title = {A quantum-mechanical tier model for phonon-driven vibrational relaxation dynamics of adsorbates at surfaces}, series = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr}, volume = {150}, journal = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr}, number = {24}, publisher = {American Institute of Physics}, address = {Melville}, issn = {0021-9606}, doi = {10.1063/1.5099902}, pages = {14}, year = {2019}, abstract = {We present a quantum-mechanical tier model for vibrational relaxation of low-lying excited states of an adsorbate vibrational mode (system), coupled to surface phonons (bath), at zero temperature. The tier model, widely used in studies of intramolecular vibrational energy redistribution in polyatomics, is adapted here to adsorbate-surface systems with the help of an embedded cluster approach, using orthogonal coordinates for the system and bath modes, and a phononic expansion of their interaction. The key idea of the model is to organize the system-bath zeroth-order vibrational space into a hierarchical structure of vibrational tiers and keep therein only vibrational states that are sequentially generated from the system-bath initial vibrational state. Each tier is generated from the previous one by means of a successor operator, derived from the system-bath interaction Hamiltonian. This sequential procedure leads to a drastic reduction of the dimension of the system-bath vibrational space. We notably show that for harmonic vibrational motion of the system and linear system-bath couplings in the system coordinate, the dimension of the tier-model vibrational basis scales as similar to N-lxv. Here, N is the number of bath modes, l is the highest-order of the phononic expansion, and l is the size of the system vibrational basis. This polynomial scaling is computationally far superior to the exponential scaling of the original zeroth-order vibrational basis, similar to M-N, with M being the number of basis functions per bath mode. In addition, since each tier is coupled only to its adjacent neighbors, the matrix representation of the system-bath Hamiltonian in this new vibrational basis has a symmetric block-tridiagonal form, with each block being very sparse. This favors the combination of the tier-model with iterative Krylov techniques, such as the Lanczos algorithm, to solve the time-dependent Schrodinger equation for the full Hamiltonian. To illustrate the method, we study vibrational relaxation of a D-Si bending mode, coupled via two-and (mainly) one-phonon interactions to a fully D-covered Si(100)-(2 x 1) surface, using a recent first-principles system-bath Hamiltonian. The results of the tier model are compared with those obtained by the Lindblad formalism of the reduced density matrix. We find that the tier model provides much more information and insight into mechanisms of vibration-phonon couplings at surfaces, and gives more reliable estimates of the adsorbate vibrational lifetimes. Moreover, the tier model might also serve as a benchmark for other approximate quantum-dynamics methods, such as multiconfiguration wavefunction approaches. Published under license by AIP Publishing.}, language = {en} } @article{LiebigHenningSarhanetal.2019, author = {Liebig, Ferenc and Henning, Ricky and Sarhan, Radwan Mohamed and Prietzel, Claudia Christina and Schmitt, Clemens Nikolaus Zeno and Bargheer, Matias and Koetz, Joachim}, title = {A simple one-step procedure to synthesise gold nanostars in concentrated aqueous surfactant solutions}, series = {RSC Advances}, volume = {9}, journal = {RSC Advances}, publisher = {RSC Publishing}, address = {London}, issn = {2046-2069}, doi = {10.1039/C9RA02384D}, pages = {23633 -- 23641}, year = {2019}, abstract = {Due to the enhanced electromagnetic field at the tips of metal nanoparticles, the spiked structure of gold nanostars (AuNSs) is promising for surface-enhanced Raman scattering (SERS). Therefore, the challenge is the synthesis of well designed particles with sharp tips. The influence of different surfactants, i.e., dioctyl sodium sulfosuccinate (AOT), sodium dodecyl sulfate (SDS), and benzylhexadecyldimethylammonium chloride (BDAC), as well as the combination of surfactant mixtures on the formation of nanostars in the presence of Ag⁺ ions and ascorbic acid was investigated. By varying the amount of BDAC in mixed micelles the core/spike-shell morphology of the resulting AuNSs can be tuned from small cores to large ones with sharp and large spikes. The concomitant red-shift in the absorption toward the NIR region without losing the SERS enhancement enables their use for biological applications and for time-resolved spectroscopic studies of chemical reactions, which require a permanent supply with a fresh and homogeneous solution. HRTEM micrographs and energy-dispersive X-ray (EDX) experiments allow us to verify the mechanism of nanostar formation according to the silver underpotential deposition on the spike surface in combination with micelle adsorption.}, language = {en} } @article{TaubertLerouxRabuetal.2019, author = {Taubert, Andreas and Leroux, Fabrice and Rabu, Pierre and de Zea Bermudez, Veronica}, title = {Advanced hybrid nanomaterials}, series = {Beilstein journal of nanotechnology}, volume = {10}, journal = {Beilstein journal of nanotechnology}, publisher = {Beilstein-Institut zur F{\"o}rderung der Chemischen Wissenschaften}, address = {Frankfurt am Main}, issn = {2190-4286}, doi = {10.3762/bjnano.10.247}, pages = {2563 -- 2567}, year = {2019}, language = {en} } @article{VishnevetskayaHildebrandNizardoetal.2019, author = {Vishnevetskaya, Natalya S. and Hildebrand, Viet and Nizardo, Noverra Mardhatillah and Ko, Chia-Hsin and Di, Zhenyu and Radulescu, Aurel and Barnsley, Lester C. and M{\"u}ller-Buschbaum, Peter and Laschewsky, Andr{\´e} and Papadakis, Christine M.}, title = {All-in-One "Schizophrenic" self-assembly of orthogonally tuned thermoresponsive diblock copolymers}, series = {Langmuir}, volume = {35}, journal = {Langmuir}, number = {19}, publisher = {American Chemical Society}, address = {Washington}, issn = {0743-7463}, doi = {10.1021/acs.langmuir.9b00241}, pages = {6441 -- 6452}, year = {2019}, abstract = {Smart, fully orthogonal switching was realized in a highly biocompatible diblock copolymer system with variable trigger-induced aqueous self-assembly. The polymers are composed of nonionic and zwitterionic blocks featuring lower and upper critical solution temperatures (LCSTs and UCSTs). In the system investigated, diblock copolymers from poly(N-isopropyl methacrylamide) (PNIPMAM) and a poly(sulfobetaine methacrylamide), systematic variation of the molar mass of the latter block allowed for shifting the UCST of the latter above the LCST of the PNIPMAM block in a salt-free condition. Thus, successive thermal switching results in "schizophrenic" micellization, in which the roles of the hydrophobic core block and the hydrophilic shell block are interchanged depending on the temperature. Furthermore, by virtue of the strong electrolyte-sensitivity of the zwitterionic polysulfobetaine block, we succeeded to shift its UCST below the LCST of the PNIPMAM block by adding small amounts of an electrolyte, thus inverting the pathway of switching. This superimposed orthogonal switching by electrolyte addition enabled us to control the switching scenarios between the two types of micelles (i) via an insoluble state, if the LCST-type cloud point is below the UCST-type cloud point, which is the case at low salt concentrations or (ii) via a molecularly dissolved state, if the LCST-type cloud point is above the UCST-type cloud point, which is the case at high salt concentrations. Systematic variation of the block lengths allowed for verifying the anticipated behavior and identifying the molecular architecture needed. The versatile and tunable self-assembly offers manifold opportunities, for example, for smart emulsifiers or for sophisticated carrier systems.}, language = {en} } @article{NaolouLendleinNeffe2019, author = {Naolou, Toufik and Lendlein, Andreas and Neffe, Axel T.}, title = {Amides as non-polymerizable catalytic adjuncts enable the ring-opening polymerization of lactide with ferrous acetate under mild conditions}, series = {Frontiers in Chemistry}, volume = {7}, journal = {Frontiers in Chemistry}, publisher = {Frontiers Research Foundation}, address = {Lausanne}, issn = {2296-2646}, doi = {10.3389/fchem.2019.00346}, pages = {12}, year = {2019}, abstract = {Sn-based catalysts are effective in the ring-opening polymerization (ROP) but are toxic. Fe(OAc)(2) used as an alternative catalyst is suitable for the ROP of lactide only at higher temperatures (>170 degrees C), associated with racemization. In the ROP of ester and amide group containing morpholinediones with Fe(OAc)(2) to polydepsipeptides at 135 degrees C, ester bonds were selectively opened. Here, it was hypothesized that ROP of lactones is possible with Fe(OAc)(2) when amides are present in the reactions mixture as Fe-ligands could increase the solubility and activity of the metal catalytic center. The ROP of lactide in the melt with Fe(OAc)(2) is possible at temperatures as low as 105 degrees C, in the presence of N-ethylacetamide or N-rnethylbenzamide as non-polymerizable catalytic adjuncts (NPCA), with high conversion (up to 99 mol\%) and yield (up to 88 mol\%). Polydispersities of polylactide decreased with decreasing reaction temperature to <= 1.1. NMR as well as polarimetric studies showed that no racemization occurred at reaction temperatures <= 145 degrees C. A kinetic study demonstrated a living chain-growth mechanism. MALDI analysis revealed that no side reactions (e.g., cyclization) occurred, though transesterification took place.}, language = {en} } @article{AloniPerovicWeitmanetal.2019, author = {Aloni, Sapir Shekef and Perovic, Milena and Weitman, Michal and Cohen, Reut and Oschatz, Martin and Mastai, Yitzhak}, title = {Amino acid-based ionic liquids as precursors for the synthesis of chiral nanoporous carbons}, series = {Nanoscale Advances}, volume = {1}, journal = {Nanoscale Advances}, number = {12}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {2516-0230}, doi = {10.1039/c9na00520j}, pages = {4981 -- 4988}, year = {2019}, abstract = {The synthesis of chiral nanoporous carbons based on chiral ionic liquids (CILs) of amino acids as precursors is described. Such unique precursors for the carbonization of CILs yield chiral carbonaceous materials with high surface area (approximate to 620 m(2) g(-1)). The enantioselectivities of the porous carbons are examined by advanced techniques such as selective adsorption of enantiomers using cyclic voltammetry, isothermal titration calorimetry, and mass spectrometry. These techniques demonstrate the chiral nature and high enantioselectivity of the chiral carbon materials. Overall, we believe that the novel approach presented here can contribute significantly to the development of new chiral carbon materials that will find important applications in chiral chemistry, such as in chiral catalysis and separation and in chiral sensors. From a scientific point of view, the approach and results reported here can significantly deepen our understanding of chirality at the nanoscale and of the structure and nature of chiral nonporous materials and surfaces.}, language = {en} } @article{HeckKanehiraKneippetal.2019, author = {Heck, Christian and Kanehira, Yuya and Kneipp, Janina and Bald, Ilko}, title = {Amorphous Carbon Generation as a Photocatalytic Reaction on DNA-Assembled Gold and Silver Nanostructures}, series = {Molecules}, volume = {24}, journal = {Molecules}, number = {12}, publisher = {MDPI}, address = {Basel}, issn = {1420-3049}, doi = {10.3390/molecules24122324}, pages = {10}, year = {2019}, abstract = {Background signals from in situ-formed amorphous carbon, despite not being fully understood, are known to be a common issue in few-molecule surface-enhanced Raman scattering (SERS). Here, discrete gold and silver nanoparticle aggregates assembled by DNA origami were used to study the conditions for the formation of amorphous carbon during SERS measurements. Gold and silver dimers were exposed to laser light of varied power densities and wavelengths. Amorphous carbon prevalently formed on silver aggregates and at high power densities. Time-resolved measurements enabled us to follow the formation of amorphous carbon. Silver nanolenses consisting of three differently-sized silver nanoparticles were used to follow the generation of amorphous carbon at the single-nanostructure level. This allowed observation of the many sharp peaks that constitute the broad amorphous carbon signal found in ensemble measurements. In conclusion, we highlight strategies to prevent amorphous carbon formation, especially for DNA-assembled SERS substrates.}, language = {en} } @article{PoghosyanAdamyanShahinyanetal.2019, author = {Poghosyan, Armen H. and Adamyan, Maksim P. and Shahinyan, Aram A. and Koetz, Joachim}, title = {AOT Bilayer Adsorption on Gold Surfaces}, series = {The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces \& biophysical chemistry}, volume = {123}, journal = {The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces \& biophysical chemistry}, number = {4}, publisher = {American Chemical Society}, address = {Washington}, issn = {1520-6106}, doi = {10.1021/acs.jpcb.8b11471}, pages = {948 -- 953}, year = {2019}, abstract = {A molecular dynamics study was done to reveal the adsorption properties of sodium dioctyl sulfosuccinate (AOT) bilayers on gold Au(111) surfaces. Examining the rotational mobility of AOT molecules, we track that the correlation time of AOT molecules on the adsorbed layer is much higher. The data estimating the diffusive motion of AOT molecule show a substantially lower rate of diffusion (similar to 10(-10) cm(2)/s) in the adsorbed layers in comparison to other ones. The results show that an adsorbed layer is more rigid, whereas the outer layers undergo considerable lateral and vertical fluctuations.}, language = {en} } @article{KleinpeterKoch2019, author = {Kleinpeter, Erich and Koch, Andreas}, title = {Benzenium Ion}, series = {The journal of physical chemistry : A, Molecules, spectroscopy, kinetics, environment \& general theory}, volume = {123}, journal = {The journal of physical chemistry : A, Molecules, spectroscopy, kinetics, environment \& general theory}, number = {20}, publisher = {American Chemical Society}, address = {Washington}, issn = {1089-5639}, doi = {10.1021/acs.jpca.9b03121}, pages = {4443 -- 4451}, year = {2019}, abstract = {The spatial magnetic properties, through-space NMR shieldings (TSNMRSs), of the benzenium cation (C6H7+) 1 and of +/- I/M-substituted analogues C6H6X+ 3-8 [X = -Me, -CF3, -NH2, -NO2, -NO, -SiH3] have been calculated using the gauge-independent atomic orbital perturbation method employing the nucleus-independent chemical shift concept, and iso-chemical-shielding surfaces of various sizes and directions have been observed. The TSNMRS values were employed to compare the spatial magnetic properties (TSNMRS) of benzene and the benzenium ion 1 and then further compared with analogues 3-8, to answer the question whether the electronic structures of 1 and 3-8 are still similar to those of aromatic species or somewhat similar to the antiaromatic cyclopentadienyl cation 2, supported by structural data and delta(C-13)/ppm values.}, language = {en} } @article{KleinpeterKoch2019, author = {Kleinpeter, Erich and Koch, Andreas}, title = {Benzyne - an acetylene- or cumulene-like electronic structure?}, series = {Tetrahedron}, volume = {75}, journal = {Tetrahedron}, number = {33}, publisher = {Elsevier}, address = {Oxford}, issn = {0040-4020}, doi = {10.1016/j.tet.2019.07.011}, pages = {4663 -- 4668}, year = {2019}, abstract = {The spatial magnetic properties, through-space NMR shieldings (TSNMRS), of benzyne 1 and analogues (benzene 2, 1,2,3-cyclohexatriene 3, cyclohexen-3-yne 4, cyclohexen-4-yne 5, cyclohexyne 6) have been calculated using the GIAO perturbation method employing the nucleus independent chemical shift (NICS) concept and visualized as iso-chemical-shielding surfaces (ICSS) of various size and direction. The TSNMRS values could be employed to compare the diatropic ring current effects of benzene and benzyne, and, when compared with the spatial magnetic properties of the analogues, to answer the question whether the benzyne electronic structure is more acetylene- or cumulene-like, supported by structural data and delta(C-13)/ppm values. (C) 2019 Published by Elsevier Ltd.}, language = {en} } @article{SassStoeckleinKlevesathetal.2019, author = {Sass, Stephan and St{\"o}cklein, Walter F. M. and Klevesath, Anja and Hurpin, Jeanne and Menger, Marcus and Hille, Carsten}, title = {Binding affinity data of DNA aptamers for therapeutic anthracyclines from microscale thermophoresis and surface plasmon resonance spectroscopy}, series = {The analyst : the analytical journal of the Royal Society of Chemistry}, volume = {144}, journal = {The analyst : the analytical journal of the Royal Society of Chemistry}, number = {20}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {0003-2654}, doi = {10.1039/c9an01247h}, pages = {6064 -- 6073}, year = {2019}, abstract = {Anthracyclines like daunorubicin (DRN) and doxorubicin (DOX) play an undisputed key role in cancer treatment, but their chronic administration can cause severe side effects. For precise anthracycline analytical systems, aptamers are preferable recognition elements. Here, we describe the detailed characterisation of a single-stranded DNA aptamer DRN-10 and its truncated versions for DOX and DRN detection. Binding affinities were determined from surface plasmon resonance (SPR) and microscale thermophoresis (MST) and combined with conformational data from circular dichroism (CD). Both aptamers displayed similar nanomolar binding affinities to DRN and DOX, even though their rate constants differed as shown by SPR recordings. SPR kinetic data unravelled a two-state reaction model including a 1 : 1 binding and a subsequent conformational change of the binding complex. This model was supported by CD spectra. In addition, the dissociation constants determined with MST were always lower than that from SPR, and especially for the truncated aptamer they differed by two orders of magnitude. This most probably reflects the methodological difference, namely labelling for MST vs. immobilisation for SPR. From CD recordings, we suggested a specific G-quadruplex as structural basis for anthracycline binding. We concluded that the aptamer DRN-10 is a promising recognition element for anthracycline detection systems and further selected aptamers can be also characterised with the combined methodological approach presented here.}, language = {en} } @article{JetzschmannTankJagerszkietal.2019, author = {Jetzschmann, Katharina J. and Tank, Steffen and Jagerszki, Gyula and Gyurcsanyi, Robert E. and Wollenberger, Ulla and Scheller, Frieder W.}, title = {Bio-Electrosynthesis of Vectorially Imprinted Polymer Nanofilms for Cytochrome P450cam}, series = {ChemElectroChem}, volume = {6}, journal = {ChemElectroChem}, number = {6}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {2196-0216}, doi = {10.1002/celc.201801851}, pages = {1818 -- 1823}, year = {2019}, abstract = {A new approach for synthesizing a vectorially imprinted polymer (VIP) is presented for the microbial cytochrome P450cam enzyme. A surface attached binding motif of a natural reaction partner of the target protein, putidaredoxin (Pdx), is the anchor to the underlying transducer. The 15 amino acid peptide anchor, which stems from the largest continuous amino acid chain within the binding site of Pdx was modified: (i) internal cysteines were replaced by serines to prevent disulfide bond formation; (ii) 2 ethylene glycol units were attached to the N-terminus as a spacer region; and (iii) an N-terminal cysteine was added to allow the immobilization on the gold electrode surface. Immobilization on GCE was achieved via an N-(1-pyrenyl)maleimide (NPM) cross-linker. In this way oriented immobilization of P450cam was accomplished by binding it to a peptide-modified gold or glassy carbon electrode (GCE) prior to the electrosynthesis of a polymer nanofilm around the immobilized target. This VIP nanofilm enabled reversible oriented docking of P450cam as it is indicated by the catalytic oxygen reduction via direct electron transfer between the enzyme and the underlying electrode. Catalysis of oxygen reduction by P450cam bound to the VIP-modified GCE was used to measure rebinding to the VIP. The mild coupling of an oxidoreductase with the electrode may be appropriate for realizing electrode-driven substrate conversion by instable P450 enzymes without the need of NADPH co-factor.}, language = {en} } @article{ReinickeFischerBramskietal.2019, author = {Reinicke, Stefan and Fischer, Thilo and Bramski, Julia and Pietruszka, J{\"o}rg and B{\"o}ker, Alexander}, title = {Biocatalytically active microgels by precipitation polymerization of N-isopropyl acrylamide in the presence of an enzyme}, series = {RSC Advances}, volume = {9}, journal = {RSC Advances}, number = {49}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {2046-2069}, doi = {10.1039/c9ra04000e}, pages = {28377 -- 28386}, year = {2019}, abstract = {We present a novel protocol for the synthesis of enzymatically active microgels. The protocol is based on the precipitation polymerization of N-isopropylacrylamide (NIPAm) in the presence of an enzyme and a protein binding comonomer. A basic investigation on the influence of different reaction parameters such as monomer concentration and reaction temperature on the microgel size and size distribution is performed and immobilization yields are determined. Microgels exhibiting hydrodynamic diameters between 100 nm and 1 mu m and narrow size distribution could be synthesized while about 31-44\% of the enzyme present in the initial reaction mixture can be immobilized. Successful immobilization including a verification of enzymatic activity of the microgels is achieved for glucose oxidase (GOx) and 2-deoxy-d-ribose-5-phosphate aldolase (DERA). The thermoresponsive properties of the microgels are assessed and discussed in the light of activity evolution with temperature. The positive correlation of enzymatic activity with temperature for the GOx containing microgel originates from a direct interaction of the enzyme with the PNIPAm based polymer matrix whose magnitude is highly influenced by temperature.}, language = {en} } @article{LendleinBalkTarazonaetal.2019, author = {Lendlein, Andreas and Balk, Maria and Tarazona, Natalia A. and Gould, Oliver E. C.}, title = {Bioperspectives for Shape-Memory Polymers as Shape Programmable, Active Materials}, series = {Biomacromolecules : an interdisciplinary journal focused at the interface of polymer science and the biological sciences}, volume = {20}, journal = {Biomacromolecules : an interdisciplinary journal focused at the interface of polymer science and the biological sciences}, number = {10}, publisher = {American Chemical Society}, address = {Washington}, issn = {1525-7797}, doi = {10.1021/acs.biomac.9b01074}, pages = {3627 -- 3640}, year = {2019}, abstract = {Within the natural world, organisms use information stored in their material structure to generate a physical response to a wide variety of environmental changes. The ability to program synthetic materials to intrinsically respond to environmental changes in a similar manner has the potential to revolutionize material science. By designing polymeric devices capable of responsively changing shape or behavior based on information encoded into their structure, we can create functional physical behavior, including a shape memory and an actuation capability. Here we highlight the stimuli-responsiveness and shape-changing ability of biological materials and biopolymer-based materials, plus their potential biomedical application, providing a bioperspective on shape-memory materials. We address strategies to incorporate a shape memory (actuation) function in polymeric materials, conceptualized in terms of its relationship with inputs (environmental stimuli) and outputs (shape change). Challenges and opportunities associated with the integration of several functions in a single material body to achieve multifunctionality are discussed. Finally, we describe how elements that sense, convert, and transmit stimuli have been used to create multisensitive materials.}, language = {en} } @article{KochStamboliyskaMikhovaetal.2019, author = {Koch, Andreas and Stamboliyska, Bistra and Mikhova, Bozhana and Breznica-Selmani, Pranvera and Mladenovska, Kristina and Popovski, Emil}, title = {Calculations of C-13 NMR chemical shifts and F-C coupling constants of ciprofloxacin}, series = {Magnetic resonance in chemistry}, volume = {57}, journal = {Magnetic resonance in chemistry}, number = {4}, publisher = {Wiley}, address = {Hoboken}, issn = {0749-1581}, doi = {10.1002/mrc.4827}, pages = {75 -- 84}, year = {2019}, abstract = {Ciprofloxacin is a widely used fluoroquinolone antibiotic. In this work, a comprehensive evaluation of MP2 and DFT with different functionals and basis sets was carried out to select the most suitable level of theory for the study of the NMR properties of ciprofloxacin. Their relative predictive capabilities were evaluated comparing the theoretically predicted and experimental spectral data. Our computational results indicated that in contrast to the solid state, the molecule of ciprofloxacin does not exist as a zwitterion in gaseous state. The results of the calculations of the chemical shifts most close to the experimental were obtained with B3LYP/aug-cc-pVDZ. The F-C coupling constants were calculated systematically with different DFT methods and several basis sets. In general, the calculations of the coupling constants with the BHandH computational method including the applied in this work 6-311++G**, EPRII, and EPRIII basis sets showed a good reproducibility of the experimental values of the coupling constants.}, language = {en} } @article{HauserWodtkeTonderaetal.2019, author = {Hauser, Sandra and Wodtke, Robert and Tondera, Christoph and Wodtke, Johanna and Neffe, Axel T. and Hampe, Jochen and Lendlein, Andreas and L{\"o}ser, Reik and Pietzsch, Jens}, title = {Characterization of Tissue Transglutaminase as a Potential Biomarker for Tissue Response toward Biomaterials}, series = {ACS biomaterials science \& engineering}, volume = {5}, journal = {ACS biomaterials science \& engineering}, number = {11}, publisher = {American Chemical Society}, address = {Washington}, issn = {2373-9878}, doi = {10.1021/acsbiomaterials.9b01299}, pages = {5979 -- 5989}, year = {2019}, abstract = {Tissue transglutaminase (TGase 2) is proposed to be important for biomaterial-tissue interactions due to its presence and versatile functions in the extracellular environment. TGase 2 catalyzes the cross-linking of proteins through its Ca2+-dependent acyltransferase activity. Moreover, it enhances the interactions between fibronectin and integrins, which in turn mediates the adhesion, migration, and motility of the cells. TGase 2 is also a key player in the pathogenesis of fibrosis. In this study, we investigated whether TGase 2 is present at the biomaterial tissue interface and might serve as an informative biomarker for the visualization of tissue response toward gelatin-based biomaterials. Two differently cross-linked hydrogels were used, which were obtained by the reaction of gelatin with lysine diisocyanate ethyl ester. The overall expression of TGase 2 by endothelial cells, macrophages, and granulocytes was partly influenced by contact to the hydrogels or their degradation products, although no clear correlation was evidenced. In contrast, the secretion of TGase 2 differed remarkably between the different cells, indicating that it might be involved in the cellular reaction toward gelatin-based hydrogels. The hydrogels were implanted subcutaneously in immunocompetent, hairless SKH1-Elite mice. Ex vivo immunohistochemical analysis of tissue sections over 112 days revealed enhanced expression of TGase 2 around the hydrogels, in particular at days 14 and 21 post-implantation. The incorporation of fluorescently labeled cadaverine derivatives for the detection of active TGase 2 was in accordance with the results of the expression analysis. The presence of an irreversible inhibitor of TGase 2 led to attenuated incorporation of the cadaverines, which verified the catalytic action of TGase 2. Our in vitro and ex vivo results verified TGase 2 as a potential biomarker for tissue response toward gelatin-based hydrogels. In vivo, no TGase 2 activity was detectable, which is mainly attributed to the unfavorable physicochemical properties of the cadaverine probe used.}, language = {en} } @article{ZhangBehlPengetal.2019, author = {Zhang, Pengfei and Behl, Marc and Peng, Xingzhou and Balk, Maria and Lendlein, Andreas}, title = {Chemoresponsive Shape-Memory Effect of Rhodium-Phosphine Coordination Polymer Networks}, series = {Chemistry of materials : a publication of the American Chemical Society}, volume = {31}, journal = {Chemistry of materials : a publication of the American Chemical Society}, number = {15}, publisher = {American Chemical Society}, address = {Washington}, issn = {0897-4756}, doi = {10.1021/acs.chemmater.9b00363}, pages = {5402 -- 5407}, year = {2019}, abstract = {Chemoresponsive polymers are of technological significance for smart sensors or systems capable of molecular recognition. An important key requirement for these applications is the material's structural integrity after stimulation. We explored whether covalently cross-linked metal ion-phosphine coordination polymers (MPN) can be shaped into any temporary shape and are capable of recovering from this upon chemoresponsive exposure to triphenylphosphine (Ph3P) ligands, whereas the MPN provide structural integrity. Depending on the metal-ion concentration used during synthesis of the MPN, the degree of swelling of the coordination polymer networks could be adjusted. Once the MPN was immersed into Ph3P solution, the reversible ligand-exchange reaction between the metal ions and the free Ph3P in solution causes a decrease of the coordination cross-link density in MPN again. The Ph3P-treated MPN was able to maintain its original shape, indicating a certain stability of shape even after stimulation. In this way, chemoresponsive control of the elastic properties (increase in volume and decrease of mechanical strength) of the MPN was demonstrated. This remarkable behavior motivated us to explore whether the MPN are capable of a chemoresponsive shape-memory effect. In initial experiments, shape fixity of around 60\% and shape recovery of almost 90\% were achieved when the MPN was exposed to Ph3P in case of rhodium. Potential applications for chemoresponsive shape-memory systems could be shapable semiconductors, e.g., for lighting or catalysts, which provide catalytic activity on demand.}, language = {en} } @article{BhuvaneshMachatschekLysyakovaetal.2019, author = {Bhuvanesh, Thanga and Machatschek, Rainhard Gabriel and Lysyakova, Liudmila and Kratz, Karl and Schulz, Burkhard and Ma, Nan and Lendlein, Andreas}, title = {Collagen type-IV Langmuir and Langmuir-Schafer layers as model biointerfaces to direct stem cell adhesion}, series = {Biomedical materials : materials for tissue engineering and regenerative medicine}, volume = {14}, journal = {Biomedical materials : materials for tissue engineering and regenerative medicine}, number = {2}, publisher = {Inst. of Physics Publ.}, address = {Bristol}, issn = {1748-6041}, doi = {10.1088/1748-605X/aaf464}, pages = {17}, year = {2019}, abstract = {In biomaterial development, the design of material surfaces that mimic the extra-cellular matrix (ECM) in order to achieve favorable cellular instruction is rather challenging. Collagen-type IV (Col-IV), the major scaffolding component of Basement Membranes (BM), a specialized ECM with multiple biological functions, has the propensity to form networks by self-assembly and supports adhesion of cells such as endothelial cells or stem cells. The preparation of biomimetic Col-IV network-like layers to direct cell responses is difficult. We hypothesize that the morphology of the layer, and especially the density of the available adhesion sites, regulates the cellular adhesion to the layer. The Langmuir monolayer technique allows for preparation of thin layers with precisely controlled packing density at the air-water (A-W) interface. Transferring these layers onto cell culture substrates using the Langmuir-Schafer (LS) technique should therefore provide a pathway for preparation of BM mimicking layers with controlled cell adherence properties. In situ characterization using ellipsometry and polarization modulation-infrared reflection absorption spectroscopy of Col-IV layer during compression at the A-W interface reveal that there is linear increase of surface molecule concentration with negligible orientational changes up to a surface pressure of 25 mN m(-1). Smooth and homogeneous Col-IV network-like layers are successfully transferred by LS method at 15 mN m(-1) onto poly(ethylene terephthalate) (PET), which is a common substrate for cell culture. In contrast, the organization of Col-IV on PET prepared by the traditionally employed solution deposition method results in rather inhomogeneous layers with the appearance of aggregates and multilayers. Progressive increase in the number of early adherent mesenchymal stem cells (MSCs) after 24 h by controlling the areal Col-IV density by LS transfer at 10, 15 and 20 mN m(-1) on PET is shown. The LS method offers the possibility to control protein characteristics on biomaterial surfaces such as molecular density and thereby, modulate cell responses.}, language = {en} } @article{RiebeErlerBrinkmannetal.2019, author = {Riebe, Daniel and Erler, Alexander and Brinkmann, Pia and Beitz, Toralf and L{\"o}hmannsr{\"o}ben, Hans-Gerd and Gebbers, Robin}, title = {Comparison of Calibration Approaches in Laser-Induced Breakdown Spectroscopy for Proximal Soil Sensing in Precision Agriculture}, series = {Sensors}, volume = {19}, journal = {Sensors}, number = {23}, publisher = {MDPI}, address = {Basel}, issn = {1424-8220}, doi = {10.3390/s19235244}, pages = {16}, year = {2019}, abstract = {The lack of soil data, which are relevant, reliable, affordable, immediately available, and sufficiently detailed, is still a significant challenge in precision agriculture. A promising technology for the spatial assessment of the distribution of chemical elements within fields, without sample preparation is laser-induced breakdown spectroscopy (LIBS). Its advantages are contrasted by a strong matrix dependence of the LIBS signal which necessitates careful data evaluation. In this work, different calibration approaches for soil LIBS data are presented. The data were obtained from 139 soil samples collected on two neighboring agricultural fields in a quaternary landscape of northeast Germany with very variable soils. Reference analysis was carried out by inductively coupled plasma optical emission spectroscopy after wet digestion. The major nutrients Ca and Mg and the minor nutrient Fe were investigated. Three calibration strategies were compared. The first method was based on univariate calibration by standard addition using just one soil sample and applying the derived calibration model to the LIBS data of both fields. The second univariate model derived the calibration from the reference analytics of all samples from one field. The prediction is validated by LIBS data of the second field. The third method is a multivariate calibration approach based on partial least squares regression (PLSR). The LIBS spectra of the first field are used for training. Validation was carried out by 20-fold cross-validation using the LIBS data of the first field and independently on the second field data. The second univariate method yielded better calibration and prediction results compared to the first method, since matrix effects were better accounted for. PLSR did not strongly improve the prediction in comparison to the second univariate method.}, language = {en} } @article{ShainyanKleinpeterSuslova2019, author = {Shainyan, Bagrat A. and Kleinpeter, Erich and Suslova, E. N.}, title = {Conformational Analysis of (1,1′-Phenyl-1,1′-silacyclohex-1-yl)disiloxane}, series = {Russian journal of general chemistry}, volume = {89}, journal = {Russian journal of general chemistry}, number = {4}, publisher = {Pleiades Publ.}, address = {New York}, issn = {1070-3632}, doi = {10.1134/S1070363219040121}, pages = {713 -- 716}, year = {2019}, abstract = {The DFT and MP2 theoretical conformational analysis of the recently synthesized (1,1-phenyl-1,1-silacyclohex-1-yl)disiloxane has revealed the energetic preference of the Ph-ax,Ph-ax conformer. The Ph-ax,Ph-ax: Ph-ax,Ph-eq: Ph-eq,Ph-eq conformers ratio has been estimated as of 46.6: 33.1: 20.3 from the M062X/6-311G(d,p) free energy simulation, suggesting the possibility of detecting individual conformers experimentally, e.g., by low-temperature H-1 and C-13 NMR spectroscopy. However, only the presence of several conformers has been detected by means of H-1 NMR spectroscopy at 113 K; determination of the (Hz) and G(\#) (kcal/mol) parameters for the 6-membered ring interconversion has been impossible due to the signals broadening at low temperature, signal temperature shifts, and extremely low barrier of ring inversion at T-c < 113 K.}, language = {en} } @article{ShouBremerRindfleischetal.2019, author = {Shou, Keyun and Bremer, Anne and Rindfleisch, Tobias and Knox-Brown, Patrick and Hirai, Mitsuhiro and Rekas, Agata and Garvey, Christopher J. and Hincha, Dirk K. and Stadler, Andreas M. and Thalhammer, Anja}, title = {Conformational selection of the intrinsically disordered plant stress protein COR15A in response to solution osmolarity - an X-ray and light scattering study}, series = {Physical chemistry, chemical physics : a journal of European Chemical Societies}, volume = {21}, journal = {Physical chemistry, chemical physics : a journal of European Chemical Societies}, number = {34}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1463-9076}, doi = {10.1039/c9cp01768b}, pages = {18727 -- 18740}, year = {2019}, abstract = {The plant stress protein COR15A stabilizes chloroplast membranes during freezing. COR15A is an intrinsically disordered protein (IDP) in aqueous solution, but acquires an alpha-helical structure during dehydration or the increase of solution osmolarity. We have used small- and wide-angle X-ray scattering (SAXS/WAXS) combined with static and dynamic light scattering (SLS/DLS) to investigate the structural and hydrodynamic properties of COR15A in response to increasing solution osmolarity. Coarse-grained ensemble modelling allowed a structure-based interpretation of the SAXS data. Our results demonstrate that COR15A behaves as a biomacromolecule with polymer-like properties which strongly depend on solution osmolarity. Biomacromolecular self-assembly occurring at high solvent osmolarity is initiated by the occurrence of two specific structural subpopulations of the COR15A monomer. The osmolarity dependent structural selection mechanism is an elegant way for conformational regulation and assembly of COR15A. It highlights the importance of the polymer-like properties of IDPs for their associated biological function.}, language = {en} } @article{ZuAmsalemEggeretal.2019, author = {Zu, Fengshuo and Amsalem, Patrick and Egger, David A. and Wang, Rongbin and Wolff, Christian Michael and Fang, Honghua and Loi, Maria Antonietta and Neher, Dieter and Kronik, Leeor and Duhm, Steffen and Koch, Norbert}, title = {Constructing the Electronic Structure of CH3NH3PbI3 and CH3NH3PbBr3 Perovskite Thin Films from Single-Crystal Band Structure Measurements}, series = {The journal of physical chemistry letters}, volume = {10}, journal = {The journal of physical chemistry letters}, number = {3}, publisher = {American Chemical Society}, address = {Washington}, issn = {1948-7185}, doi = {10.1021/acs.jpclett.8b03728}, pages = {601 -- 609}, year = {2019}, abstract = {Photovoltaic cells based on halide perovskites, possessing remarkably high power conversion efficiencies have been reported. To push the development of such devices further, a comprehensive and reliable understanding of their electronic properties is essential but presently not available. To provide a solid foundation for understanding the electronic properties of polycrystalline thin films, we employ single-crystal band structure data from angle-resolved photoemission measurements. For two prototypical perovskites (CH3NH3PbBr3 and CH3NH3PbI3), we reveal the band dispersion in two high-symmetry directions and identify the global valence band maxima. With these benchmark data, we construct "standard" photoemission spectra from polycrystalline thin film samples and resolve challenges discussed in the literature for determining the valence band onset with high reliability. Within the framework laid out here, the consistency of relating the energy level alignment in perovskite-based photovoltaic and optoelectronic devices with their functional parameters is substantially enhanced.}, language = {en} } @article{DasElTawargyKhechineetal.2019, author = {Das, Abhijna and El-Tawargy, Ahmed S. and Khechine, Emna and Noack, Sebastian and Schlaad, Helmut and Reiter, G{\"u}nter and Reiter, Renate}, title = {Controlling Nucleation in Quasi-Two-Dimensional Langmuir Poly(L-lactide) Films through Variation of the Rate of Compression}, series = {Langmuir}, volume = {35}, journal = {Langmuir}, number = {18}, publisher = {American Chemical Society}, address = {Washington}, issn = {0743-7463}, doi = {10.1021/acs.langmuir.9b00619}, pages = {6129 -- 6136}, year = {2019}, abstract = {We studied morphological changes in a quasi-two-dimensional Langmuir film of low molar mass poly(L-lactide) upon increasing the surface density, starting from randomly distributed molecules to a homogeneous monolayer of closely packed molecules, followed by nucleation and growth of mesoscopic, three-dimensional clusters from an overcompressed monolayer. The corresponding nucleation density of mesoscopic clusters within the monolayer can be tailored through variation of the rate of compression. For a given surface density and temperature, the nucleation probability was found to increase linearly with the rate of compression, allowing to adjust the density of mesoscopic clusters over nearly 2 orders magnitude.}, language = {en} } @article{WalczakSavateevHeskeetal.2019, author = {Walczak, Ralf and Savateev, Aleksandr and Heske, Julian and Tarakina, Nadezda V. and Sahoo, Sudhir and Epping, Jan D. and Kuehne, Thomas D. and Kurpil, Bogdan and Antonietti, Markus and Oschatz, Martin}, title = {Controlling the strength of interaction between carbon dioxide and nitrogen-rich carbon materials by molecular design}, series = {Sustainable energy \& fuels}, volume = {3}, journal = {Sustainable energy \& fuels}, number = {10}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {2398-4902}, doi = {10.1039/c9se00486f}, pages = {2819 -- 2827}, year = {2019}, abstract = {Thermal treatment of hexaazatriphenylene-hexacarbonitrile (HAT-CN) in the temperature range from 500 degrees C to 700 degrees C leads to precise control over the degree of condensation, and thus atomic construction and porosity of the resulting C2N-type materials. Depending on the condensation temperature of HAT-CN, nitrogen contents of more than 30 at\% can be reached. In general, these carbons show adsorption properties which are comparable to those known for zeolites but their pore size can be adjusted over a wider range. At condensation temperatures of 525 degrees C and below, the uptake of nitrogen gas remains negligible due to size exclusion, but the internal pores are large and polarizing enough that CO2 can still adsorb on part of the internal surface. This leads to surprisingly high CO2 adsorption capacities and isosteric heat of adsorption of up to 52 kJ mol(-1). Theoretical calculations show that this high binding enthalpy arises from collective stabilization effects from the nitrogen atoms in the C2N layers surrounding the carbon atom in the CO2 molecule and from the electron acceptor properties of the carbon atoms from C2N which are in close proximity to the oxygen atoms in CO2. A true CO2 molecular sieving effect is achieved for the first time in such a metal-free organic material with zeolite-like properties, showing an IAST CO2/N-2 selectivity of up to 121 at 298 K and a N-2/CO2 ratio of 90/10 without notable changes in the CO2 adsorption properities over 80 cycles.}, language = {en} } @article{JiaFriebeSchubertetal.2019, author = {Jia, He and Friebe, Christian and Schubert, Ulrich S. and Zhang, Xiaozhe and Quan, Ting and Lu, Yan and Gohy, Jean-Francois}, title = {Core-Shell Nanoparticles with a Redox Polymer Core and a Silica Porous Shell as High-Performance Cathode Material for Lithium-Ion Batteries}, series = {Energy technology : generation, conversion, storage, distribution}, volume = {8}, journal = {Energy technology : generation, conversion, storage, distribution}, number = {3}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {2194-4288}, doi = {10.1002/ente.201901040}, pages = {8}, year = {2019}, abstract = {A facile and novel method for the fabrication of core-shell nanoparticles (PTMA@SiO2) based on a poly(2,2,6,6-tetramethylpiperidinyloxy-4-yl methacrylate) (PTMA) core and a porous SiO2 shell is reported. The core-shell nanoparticles are further self-assembled with negatively charged multi-walled carbon nanotubes (MWCNTs), which results in the formation of a free-standing cathode electrode. The porous SiO2 shell not only effectively improves the stability of the linear PTMA redox polymer with low molar mass in organic electrolytes but also leads to the uniform dispersion of PTMA active units in the MWCNTs conductive network. The PTMA@SiO2@MWCNT composite electrode exhibits a specific capacity as high as 73.8 mAh g at 1 C and only 0.11\% capacity loss per cycle at a rate of 2 C.}, language = {en} } @article{JiaQuanLiuetal.2019, author = {Jia, He and Quan, Ting and Liu, Xuelian and Bai, Lu and Wang, Jiande and Boujioui, Fadoi and Ye, Ran and Vald, Alexandru and Lu, Yan and Gohy, Jean-Francois}, title = {Core-shell nanostructured organic redox polymer cathodes with superior performance}, series = {Nano Energy}, volume = {64}, journal = {Nano Energy}, publisher = {Elsevier}, address = {Amsterdam}, issn = {2211-2855}, doi = {10.1016/j.nanoen.2019.103949}, pages = {9}, year = {2019}, abstract = {Core-shell nanoparticles stabilized by a cationic surfactant are prepared from the poly(2,2,6,6-tetra-methylpiperidinyloxy-4-yl methacrylate) redox polymer. The nanoparticles are further self-assembled with negatively charged reduced graphene oxide nanosheets and negatively charged mull-walled carbon nanotubes. This results in the formation of a free-standing cathode with a layered nanostructure and a high content of redox polymer that exhibits 100\% utilization of the active substance with a measured capacity as high as 105 mAh/g based on the whole weight of the electrode.}, language = {en} } @article{KruegerKellingLinkeretal.2019, author = {Krueger, Tobias and Kelling, Alexandra and Linker, Torsten and Schilde, Uwe}, title = {Crystal structures of three cyclohexane‑based γ‑spirolactams}, series = {BMC Chemistry}, volume = {13}, journal = {BMC Chemistry}, number = {69}, publisher = {Springer International Publishing}, address = {Basel}, issn = {2661-801X}, doi = {10.1186/s13065-019-0586-7}, pages = {9}, year = {2019}, abstract = {The title compounds, 2-azaspiro[4.5]deca-1-one, C₉H₁₅NO, (1a), cis-8-methyl-2-azaspiro[4.5]deca-1-one, C₁₀H₁₇NO, (1b), and trans-8-methyl-2-azaspiro[4.5]deca-1-one, C₁₀H₁₇NO, (1c), were synthesized from benzoic acids 2 in only 3 steps in high yields. Crystallization from n-hexane afforded single crystals, suitable for X-ray diffraction. Thus, the configurations, conformations, and interesting crystal packing effects have been determined unequivocally. The bicyclic skeleton consists of a lactam ring, attached by a spiro junction to a cyclohexane ring. The lactam ring adopts an envelope conformation and the cyclohexane ring has a chair conformation. The main difference between compound 1b and compound 1c is the position of the carbonyl group on the 2-pyrrolidine ring with respect to the methyl group on the 8-position of the cyclohexane ring, which is cis (1b) or trans (1c). A remarkable feature of all three compounds is the existence of a mirror plane within the molecule. Given that all compounds crystallize in centrosymmetric space groups, the packing always contains interesting enantiomer-like pairs. Finally, the structures are stabilized by intermolecular N-H···O hydrogen bonds.}, language = {en} } @article{AdemMbavengKueteetal.2019, author = {Adem, Fozia A. and Mbaveng, Armelle T. and Kuete, Victor and Heydenreich, Matthias and Ndakala, Albert and Irungu, Beatrice and Yenesew, Abiy and Efferth, Thomas}, title = {Cytotoxicity of isoflavones and biflavonoids from Ormocarpum kirkii towards multi-factorial drug resistant cancer}, series = {Phytomedicine : international journal of phytotherapy and phytopharmacology}, volume = {58}, journal = {Phytomedicine : international journal of phytotherapy and phytopharmacology}, publisher = {Elsevier}, address = {M{\"u}nchen}, issn = {0944-7113}, doi = {10.1016/j.phymed.2019.152853}, pages = {10}, year = {2019}, abstract = {Background: While incidences of cancer are continuously increasing, drug resistance of malignant cells is observed towards almost all pharmaceuticals. Several isoflavonoids and flavonoids are known for their cytotoxicity towards various cancer cells. Methods: The cytotoxicity of compounds was determined based on the resazurin reduction assay. Caspases activation was evaluated using the caspase-Glo assay. Flow cytometry was used to analyze the cell cycle (propodium iodide (PI) staining), apoptosis (annexin V/PI staining), mitochondrial membrane potential (MMP) (JC-1) and reactive oxygen species (ROS) (H2DCFH-DA). CCRF-CEM leukemia cells were used as model cells for mechanistic studies. Results: Compounds 1, 2 and 4 displayed IC50 values below 20 mu M towards CCRF-CEM and CEM/ADR5000 leukemia cells, and were further tested towards a panel of 7 carcinoma cells. The IC50 values of the compounds against carcinoma cells varied from 16.90 mu M (in resistant U87MG.Delta EGFR glioblastoma cells) to 48.67 mu M (against HepG2 hepatocarcinoma cells) for 1, from 7.85 mu M (in U87MG.Delta EGFR cells) to 14.44 mu M (in resistant MDA-MB231/BCRP breast adenocarcinoma cells) for 2, from 4.96 mu M (towards U87MG.Delta EGFRcells) to 7.76 mu M (against MDA-MB231/BCRP cells) for 4, and from 0.07 mu M (against MDA-MB231 cells) to 2.15 mu M (against HepG2 cells) for doxorubicin. Compounds 2 and 4 induced apoptosis in CCRF-CEM cells mediated by MMP alteration and increased ROS production. Conclusion: The present report indicates that isoflavones and biflavonoids from Ormocarpum kirkii are cytotoxic compounds with the potential of being exploited in cancer chemotherapy. Compounds 2 and 4 deserve further studies to develop new anticancer drugs to fight sensitive and resistant cancer cell lines.}, language = {en} } @article{DengZouWangetal.2019, author = {Deng, Zijun and Zou, Jie and Wang, Weiwei and Nie, Yan and Tung, Wing-Tai and Ma, Nan and Lendlein, Andreas}, title = {Dedifferentiation of mature adipocytes with periodic exposure to cold}, series = {Clinical hemorheology and microcirculation : blood flow and vessels}, volume = {71}, journal = {Clinical hemorheology and microcirculation : blood flow and vessels}, number = {4}, publisher = {IOS Press}, address = {Amsterdam}, issn = {1386-0291}, doi = {10.3233/CH-199005}, pages = {415 -- 424}, year = {2019}, abstract = {Lipid-containing adipocytes can dedifferentiate into fibroblast-like cells under appropriate culture conditions, which are known as dedifferentiated fat (DFAT) cells. However, the relative low dedifferentiation efficiency with the established protocols limit their widespread applications. In this study, we found that adipocyte dedifferentiation could be promoted via periodic exposure to cold (10 degrees C) in vitro. The lipid droplets in mature adipocytes were reduced by culturing the cells in periodic cooling/heating cycles (10-37 degrees C) for one week. The periodic temperature change led to the down-regulation of the adipogenic genes (FABP4, Leptin) and up-regulation of the mitochondrial uncoupling related genes (UCP1, PGC-1 alpha, and PRDM16). In addition, the enhanced expression of the cell proliferation marker Ki67 was observed in the dedifferentiated fibroblast-like cells after periodic exposure to cold, as compared to the cells cultured in 37 degrees C. Our in vitro model provides a simple and effective approach to promote lipolysis and can be used to improve the dedifferentiation efficiency of adipocytes towards multipotent DFAT cells.}, language = {en} } @article{BedurkeKlamrothKrauseetal.2019, author = {Bedurke, Florian and Klamroth, Tillmann and Krause, Pascal and Saalfrank, Peter}, title = {Discriminating organic isomers by high harmonic generation}, series = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr}, volume = {150}, journal = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr}, number = {23}, publisher = {American Institute of Physics}, address = {Melville}, issn = {0021-9606}, doi = {10.1063/1.5096473}, pages = {10}, year = {2019}, abstract = {High Harmonic Generation (HHG) is a nonlinear optical process that provides a tunable source for high-energy photons and ultrashort laser pulses. Recent experiments demonstrated that HHG spectroscopy may also be used as an analytical tool to discriminate between randomly oriented configurational isomers of polyatomic organic molecules, namely, between the cis- and trans-forms of 1,2-dichloroethene (DCE) [M. C. H. Wong et al., Phys. Rev. A 84, 051403 (2011)]. Here, we suggest as an economic and at the same time a reasonably accurate method to compute HHG spectra for polyatomic species, Time-Dependent Configuration Interaction Singles (TD-CIS) theory in combination with extended atomic orbital bases and different models to account for ionization losses. The HHG spectra are computed for aligned and unaligned cis- and trans-DCE. For the unaligned case, a coherent averaging over possible rotational orientations is introduced. Furthermore, using TD-CIS, possible differences between the HHG spectra of cis- and trans-DCE are studied. For aligned molecules, spectral differences between cis and trans emerge, which can be related to their different point group symmetries. For unaligned, randomly oriented molecules, we also find distinct HHG spectra in partial agreement with experiment. In addition to HHG response in the frequency space, we compute time-frequency HHG spectra to gain insight into which harmonics are emitted at which time. Further differences between the two isomers emerge, suggesting time-frequency HHG as another tool to discriminate configurational isomers.}, language = {en} } @article{YangZhengTaoetal.2019, author = {Yang, Guang and Zheng, Wei and Tao, Guoqing and Wu, Libin and Zhou, Qi-Feng and Kochovski, Zdravko and Ji, Tan and Chen, Huaijun and Li, Xiaopeng and Lu, Yan and Ding, Hong-ming and Yang, Hai-Bo and Chen, Guosong and Jiang, Ming}, title = {Diversiform and Transformable Glyco-Nanostructures Constructed from Amphiphilic Supramolecular Metallocarbohydrates through Hierarchical Self-Assembly: The Balance between Metallacycles and Saccharides}, series = {ACS nano}, volume = {13}, journal = {ACS nano}, number = {11}, publisher = {American Chemical Society}, address = {Washington}, issn = {1936-0851}, doi = {10.1021/acsnano.9b07134}, pages = {13474 -- 13485}, year = {2019}, abstract = {During the past decade, self-assembly of saccharide-containing amphiphilic molecules toward bioinspired functional glycomaterials has attracted continuous attention due to their various applications in fundamental and practical areas. However, it still remains a great challenge to prepare hierarchical glycoassemblies with controllable and diversiform structures because of the complexity of saccharide structures and carbohydrate-carbohydrate interactions. Herein, through hierarchical self-assembly of modulated amphiphilic supramolecular metallocarbohydrates, we successfully prepared various well-defined glyco-nanostructures in aqueous solution, including vesicles, solid spheres, and opened vesicles depending on the molecular structures of metallocarbohydrates. More attractively, these glyco-nanostructures can further transform into other morphological structures in aqueous solutions such as worm-like micelles, tubules, and even tupanvirus-like vesicles (TVVs). It is worth mentioning that distinctive anisotropic structures including the opened vesicles (OVs) and TVVs were rarely reported in glycobased nano-objects. This intriguing diversity was mainly controlled by the subtle structural trade-off of the two major components of the amphiphiles, i.e., the saccharides and metallacycles. To further understand this precise structural control, molecular simulations provided deep physical insights on the morphology evolution and balancing of the contributions from saccharides and metallacycles. Moreover, the multivalency of glyco-nanostructures with different shapes and sizes was demonstrated by agglutination with a diversity of sugarbinding protein receptors such as the plant lectins Concanavalin A (ConA). This modular synthesis strategy provides access to systematic tuning of molecular structure and self-assembled architecture, which undoubtedly will broaden our horizons on the controllable fabrication of biomimetic glycomaterials such as biological membranes and supramolecular lectin inhibitors.}, language = {en} } @article{WeisHessKircheretal.2019, author = {Weis, Philipp and Hess, Andreas and Kircher, Gunnar and Huang, Shilin and Auernhammer, G{\"u}nter K. and Koynov, Kaloian and Butt, Hans-J{\"u}rgen and Wu, Si}, title = {Effects of Spacers on Photoinduced Reversible Solid-to-Liquid Transitions of Azobenzene-Containing Polymers}, series = {Chemistry - a European journal}, volume = {25}, journal = {Chemistry - a European journal}, number = {46}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {0947-6539}, doi = {10.1002/chem.201902273}, pages = {10946 -- 10953}, year = {2019}, abstract = {Photoisomerization in some azobenzene-containing polymers (azopolymers) results in reversible solid-to-liquid transitions because trans- and cis-azopolymers have different glass transition temperatures. This property enables photoinduced healing and processing of azopolymers with high spatiotemporal resolution. However, a general lack of knowledge about the influence of the polymer structure on photoinduced reversible solid-to-liquid transitions hinders the design of such novel polymers. Herein, the synthesis and photoresponsive behavior of new azopolymers with different lengths of spacers between the polymer backbone and the azobenzene group on the side chain are reported. Azopolymers with no and 20 methylene spacers did not show photoinduced solid-to-liquid transitions. Azopolymers with 6 or 12 methylene spacers showed photoinduced solid-to-liquid transitions. This study demonstrates that spacers are essential for azopolymers with photoinduced reversible solid-to-liquid transitions, and thus, gives an insight into how to design azopolymers for photoinduced healing and processing.}, language = {en} } @article{QinHeilSchmidtetal.2019, author = {Qin, Qing and Heil, T. and Schmidt, J. and Schmallegger, Max and Gescheidt, Georg and Antonietti, Markus and Oschatz, Martin}, title = {Electrochemical Fixation of Nitrogen and Its Coupling with Biomass Valorization with a Strongly Adsorbing and Defect Optimized Boron-Carbon-Nitrogen Catalyst}, series = {ACS Applied Energy Materials}, volume = {2}, journal = {ACS Applied Energy Materials}, number = {11}, publisher = {American Chemical Society}, address = {Washington}, issn = {2574-0962}, doi = {10.1021/acsaem.9b01852}, pages = {8359 -- 8365}, year = {2019}, abstract = {The electrochemical conversion of low-cost precursors into high-value chemicals using renewably generated electricity is a promising approach to build up an environmentally friendly energy cycle, including a storage element. The large-scale implementation of such process can, however, only be realized by the design of cost-effective electrocatalysts with high efficiency and highest stability. Here, we report the synthesis of N and B codoped porous carbons. The constructed B-N motives combine abundant unpaired electrons and frustrated Lewis pairs (FLPs). They result in desirable performance for electrochemical N-2 reduction reaction (NRR) and electrooxidation of 5-hydroxymethylfurfural (HMF) in the absence of any metal cocatalyst. A maximum Faradaic efficiency of 15.2\% with a stable NH3 production rate of 21.3 mu g h(-1) mg(-1) is obtained in NRR. Besides, 2,5-furandicarboxylic acid (FDCA) is first obtained by using non-metalbased electrocatalysts at a conversion of 71\% and with yield of 57\%. Gas adsorption experiments elucidate the relationship between the structure and the ability of the catalysts to activate the substrate molecules. This work opens up deep insights for the rational design of non-metal-based catalysts for potential electrocatalytic applications and the possible enhancement of their activity by the introduction of FLPs and point defects at grain boundaries.}, language = {en} } @article{daSilvaVarellaJonesetal.2019, author = {da Silva, Filipe Ferreira and Varella, Marcio T. do N. and Jones, Nykola C. and Hoffmann, Soren Vronning and Denifl, Stephan and Bald, Ilko and Kopyra, Janina}, title = {Electron-Induced Reactions in 3-Bromopyruvic Acid}, series = {Chemistry - a European journal}, volume = {25}, journal = {Chemistry - a European journal}, number = {21}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {0947-6539}, doi = {10.1002/chem.201806132}, pages = {5498 -- 5506}, year = {2019}, abstract = {3-Bromopyruvic acid (3BP) is a potential anticancer drug, the action of which on cellular metabolism is not yet entirely clear. The presence of a bromine atom suggests that it is also reactive towards low-energy electrons, which are produced in large quantities during tumour radiation therapy. Detailed knowledge of the interaction of 3BP with secondary electrons is a prerequisite to gain a complete picture of the effects of 3BP in different forms of cancer therapy. Herein, dissociative electron attachment (DEA) to 3BP in the gas phase has been studied both experimentally by using a crossed-beam setup and theoretically through scattering and quantum chemical calculations. These results are complemented by a vacuum ultraviolet absorption spectrum. The main fragmentation channel is the formation of Br- close to 0 eV and within several resonant features at 1.9 and 3-8 eV. At low electron energies, Br- formation proceeds through sigma* and pi* shape resonances, and at higher energies through core-excited resonances. It is found that the electron-capture cross-section is clearly increased compared with that of non-brominated pyruvic acid, but, at the same time, fragmentation reactions through DEA are significantly altered as well. The 3BP transient negative ion is subject to a lower number of fragmentation reactions than those of pyruvic acid, which indicates that 3BP could indeed act by modifying the electron-transport chains within oxidative phosphorylation. It could also act as a radio-sensitiser.}, language = {en} } @article{QinZhaoSchmalleggeretal.2019, author = {Qin, Qing and Zhao, Yun and Schmallegger, Max and Heil, Tobias and Schmidt, Johannes and Walczak, Ralf and Gescheidt-Demner, Georg and Jiao, Haijun and Oschatz, Martin}, title = {Enhanced Electrocatalytic N-2 Reduction via Partial Anion Substitution in Titanium Oxide-Carbon Composites}, series = {Angewandte Chemie : a journal of the Gesellschaft Deutscher Chemiker ; International edition}, volume = {58}, journal = {Angewandte Chemie : a journal of the Gesellschaft Deutscher Chemiker ; International edition}, number = {37}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1433-7851}, doi = {10.1002/anie.201906056}, pages = {13101 -- 13106}, year = {2019}, abstract = {The electrochemical conversion of N-2 at ambient conditions using renewably generated electricity is an attractive approach for sustainable ammonia (NH3) production. Considering the chemical inertness of N-2, rational design of efficient and stable catalysts is required. Therefore, in this work, it is demonstrated that a C-doped TiO2/C (C-TixOy/C) material derived from the metal-organic framework (MOF) MIL-125(Ti) can achieve a high Faradaic efficiency (FE) of 17.8 \%, which even surpasses most of the established noble metal-based catalysts. On the basis of the experimental results and theoretical calculations, the remarkable properties of the catalysts can be attributed to the doping of carbon atoms into oxygen vacancies (OVs) and the formation of Ti-C bonds in C-TixOy. This binding motive is found to be energetically more favorable for N-2 activation compared to the non-substituted OVs in TiO2. This work elucidates that electrochemical N-2 reduction reaction (NRR) performance can be largely improved by creating catalytically active centers through rational substitution of anions into metal oxides.}, language = {en} } @article{NieWangXuetal.2019, author = {Nie, Yan and Wang, Weiwei and Xu, Xun and Zou, Jie and Bhuvanesh, Thanga and Schulz, Burkhard and Ma, Nan and Lendlein, Andreas}, title = {Enhancement of human induced pluripotent stem cells adhesion through multilayer laminin coating}, series = {Clinical hemorheology and microcirculation : blood flow and vessels}, volume = {70}, journal = {Clinical hemorheology and microcirculation : blood flow and vessels}, number = {4}, publisher = {IOS Press}, address = {Amsterdam}, issn = {1386-0291}, doi = {10.3233/CH-189318}, pages = {531 -- 542}, year = {2019}, abstract = {Bioengineered cell substrates are a highly promising tool to govern the differentiation of stem cells in vitro and to modulate the cellular behavior in vivo. While this technology works fine for adult stem cells, the cultivation of human induced pluripotent stem cells (hiPSCs) is challenging as these cells typically show poor attachment on the bioengineered substrates, which among other effects causes substantial cell death. Thus, very limited types of surfaces have been demonstrated suitable for hiPSC cultures. The multilayer coating approach that renders the surface with diverse chemical compositions, architectures, and functions can be used to improve the adhesion of hiPSCs on the bioengineered substrates. We hypothesized that a multilayer formation based on the attraction of molecules with opposite charges could functionalize the polystyrene (PS) substrates to improve the adhesion of hiPSCs. Polymeric substrates were stepwise coated, first with dopamine to form a polydopamine (PDA) layer, second with polylysine and last with Laminin-521. The multilayer formation resulted in the variation of hydrophilicity and chemical functionality of the surfaces. Hydrophilicity was detected using captive bubble method and the amount of primary and secondary amines on the surface was quantified by fluorescent staining. The PDA layer effectively immobilized the upper layers and thereby improved the attachment of hiPSCs. Cell adhesion was enhanced on the surfaces coated with multilayers, as compared to those without PDA and/or polylysine. Moreover, hiPSCs spread well over this multilayer laminin substrate. These cells maintained their proliferation capacity and differentiation potential. The multilayer coating strategy is a promising attempt for engineering polymer-based substrates for the cultivation of hiPSCs and of interest for expanding the application scope of hiPSCs.}, language = {en} } @article{PolleyBasakHassetal.2019, author = {Polley, Nabarun and Basak, Supratim and Hass, Roland and Pacholski, Claudia}, title = {Fiber optic plasmonic sensors}, series = {Biosensors and bioelectronics : the principal international journal devoted to research, design development and application of biosensors and bioelectronics}, volume = {132}, journal = {Biosensors and bioelectronics : the principal international journal devoted to research, design development and application of biosensors and bioelectronics}, publisher = {Elsevier}, address = {Oxford}, issn = {0956-5663}, doi = {10.1016/j.bios.2019.03.020}, pages = {368 -- 374}, year = {2019}, abstract = {A simple, convenient, and inexpensive method to fabricate optical fiber based biosensors which utilize periodic hole arrays in gold films for signal transduction is reported. The process of hole array formation mainly relies on self-assembly of hydrogel microgels in combination with chemical gold film deposition and subsequent transfer of the perforated film onto an optical fiber tip. In the fabrication process solely chemical wet lab techniques are used, avoiding cost-intensive instrumentation or clean room facilities. The presented method for preparing fiber optic plasmonic sensors provides high throughput and is perfectly suited for commercialization using batch processing. The transfer of the perforated gold film onto an optical fiber tip does not affect the sensitivity of the biosensor ((420 +/- 83) nm/refractive index unit (RIU)), which is comparable to sensitivities of sensor platforms based on periodic hole arrays in gold films prepared by significantly more complex methods. Furthermore, real-time and in-line immunoassay studies with a specially designed 3D printed flow cell are presented exploiting the presented optical fiber based biosensors.}, language = {en} } @article{KosmellaKlemkeHaeusleretal.2019, author = {Kosmella, Sabine and Klemke, Bastian and H{\"a}usler, Ines and Koetz, Joachim}, title = {From gel-like Pickering emulsions to highly ordered superparamagnetic magnetite aggregates with embedded gold nanoparticles}, series = {Colloids and surfaces : an international journal devoted to the principles and applications of colloid and interface science ; A, Physicochemical and engineering aspects}, volume = {570}, journal = {Colloids and surfaces : an international journal devoted to the principles and applications of colloid and interface science ; A, Physicochemical and engineering aspects}, publisher = {Elsevier Science}, address = {Amsterdam}, issn = {0927-7757}, doi = {10.1016/j.colsurfa.2019.03.017}, pages = {331 -- 338}, year = {2019}, abstract = {Pickering emulsions with two types of nanoparticles, i.e., superparamagnetic magnetite nanoparticles dispersed in n-hexane and gold nanoparticles dispersed in water, were formed by rigorous mixing in presence of surface active polymeric surfactants. Monodisperse magnetite nanoparticles with a mean particle size of 4 nm were obtained by a microwave-assisted synthesis in n-hexane in presence of oleic acid, and gold nanoparticles were produced in aqueous solution in presence of the hyperbranched poly(ethyleneimine) (PEI) or sodium citrate as reducing and stabilizing agent. After mixing the prepared nanoparticle dispersions in presence of the Pluronics an intermediate gel-like phase is formed. The Pickering emulsion droplets in the intermediate phase are stabilized by both types of nanoparticles, as to be seen by cryo-SEM micrographs. After separating, solvent evaporation and redispersion in water highly ordered Pluronic-stabilized superparamagnetic magnetite nanoparticle aggregates with embedded gold nanoparticles can be obtained.}, language = {en} } @article{SchultzeSchmidt2019, author = {Schultze, Christiane and Schmidt, Bernd}, title = {Functionalized Benzofurans via Microwave-Promoted Tandem Claisen-Rearrangement/5-endo-dig Cyclization}, series = {Journal of heterocyclic chemistry}, volume = {56}, journal = {Journal of heterocyclic chemistry}, number = {9}, publisher = {Wiley}, address = {Hoboken}, issn = {0022-152X}, doi = {10.1002/jhet.3671}, pages = {2619 -- 2629}, year = {2019}, abstract = {Ortho-allyloxy alkinyl benzenes undergo, upon microwave irradiation in dimethylformamide, a tandem sequence of Claisen-rearrangement and 5-endo-dig cyclization to furnish 7-allyl-substituted benzofurans. With terminal alkynes, chroman-4-ones and enaminoketones become the main products. A mechanistic proposal for this observation relies on a reaction of the starting material with the solvent dimethylformamide under the microwave conditions.}, language = {en} } @article{MachatschekLendlein2019, author = {Machatschek, Rainhard Gabriel and Lendlein, Andreas}, title = {Fundamental insights in PLGA degradation from thin film studies}, series = {Journal of controlled release : official journal of the Controlled Release Society and of the Japanese Society of Drug Delivery Systems}, volume = {319}, journal = {Journal of controlled release : official journal of the Controlled Release Society and of the Japanese Society of Drug Delivery Systems}, publisher = {Elsevier}, address = {New York}, issn = {0168-3659}, doi = {10.1016/j.jconrel.2019.12.044}, pages = {276 -- 284}, year = {2019}, abstract = {Poly(lactide-co-glycolide)s are commercially available degradable implant materials, which are typically selected based on specifications given by the manufacturer, one of which is their molecular weight. Here, we address the question whether variations in the chain length and their distribution affect the degradation behavior of Poly[(rac-lactide)-co-glycolide]s (PDLLGA). The hydrolysis was studied in ultrathin films at the air-water interface in order to rule out any morphological effects. We found that both for purely hydrolytic degradation as well as under enzymatic catalysis, the molecular weight has very little effect on the overall degradation kinetics of PDLLGAs. The quantitative analysis suggested a random scission mechanism. The monolayer experiments showed that an acidic micro-pH does not accelerate the degradation of PDLLGAs, in contrast to alkaline conditions. The degradation experiments were combined with interfacial rheology measurements, which showed a drastic decrease of the viscosity at little mass loss. The extrapolated molecular weight behaved similar to the viscosity, dropping to a value near to the solubility limit of PDLLGA oligomers before mass loss set in. This observation suggests a solubility controlled degradation of PDLLGA. Conclusively, the molecular weight affects the degradation of PDLLGA devices mostly in indirect ways, e.g. by determining their morphology and porosity during fabrication. Our study demonstrates the relevance of the presented Langmuir degradation method for the design of controlled release systems.}, language = {en} } @article{RosencrantzTangSchulteOsseilietal.2019, author = {Rosencrantz, Sophia and Tang, Jo Sing Julia and Schulte-Osseili, Christine and B{\"o}ker, Alexander and Rosencrantz, Ruben R.}, title = {Glycopolymers by RAFT Polymerization as Functional Surfaces for Galectin-3}, series = {Macromolecular chemistry and physics}, volume = {220}, journal = {Macromolecular chemistry and physics}, number = {20}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1022-1352}, doi = {10.1002/macp.201900293}, pages = {7}, year = {2019}, abstract = {Glycan-protein interactions are essential biological processes with many disease-related modulations and variations. One of the key proteins involved in tumor progression and metastasis is galectin-3 (Gal-3). A lot of effort is put into the development of Gal-3 inhibitors as new therapeutic agents. The avidity of glycan-protein interactions is strongly enhanced by multivalent ligand presentation. Multivalent presentation of glycans can be accomplished by utilizing glycopolymers, which are polymers with pendent glycan groups. For the production of glycopolymers, glycomonomers are synthesized by a regioselective, microwave-assisted approach starting from lactose. The resulting methacrylamide derivatives are polymerized by RAFT and immobilized on gold surfaces using the trithiocarbonate group of the chain transfer agent. Surface plasmon resonance spectroscopy enables the label free kinetic characterization of Gal-3 binding to these multivalent glycopolymers. The measurements indicate oligomerization of Gal-3 upon exposure to multivalent environments and reveal strong specific interaction with the immobilized polymers.}, language = {en} } @article{QuanGoubardBretescheHaerketal.2019, author = {Quan, Ting and Goubard-Bretesche, Nicolas and Haerk, Eneli and Kochovski, Zdravko and Mei, Shilin and Pinna, Nicola and Ballauff, Matthias and Lu, Yan}, title = {Highly Dispersible Hexagonal Carbon-MoS2-Carbon Nanoplates with Hollow Sandwich Structures for Supercapacitors}, series = {Chemistry - a European journal}, volume = {25}, journal = {Chemistry - a European journal}, number = {18}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {0947-6539}, doi = {10.1002/chem.201806060}, pages = {4757 -- 4766}, year = {2019}, abstract = {MoS2, a typical layered transition-metal dichalcogenide, is promising as an electrode material in supercapacitors. However, its low electrical conductivity could lead to limited capacitance if applied in electrochemical devices. Herein, a new nanostructure composed of hollow carbon-MoS2-carbon was successfully synthesized through an L-cysteine-assisted hydrothermal method by using gibbsite as a template and polydopamine as a carbon precursor. After calcination and etching of the gibbsite template, uniform hollow platelets, which were made of a sandwich-like assembly of partial graphitic carbon and two-dimensional layered MoS2 flakes, were obtained. The platelets showed excellent dispersibility and stability in water, and good electrical conductivity due to carbon provided by the calcination of polydopamine coatings. The hollow nanoplate morphology of the material provided a high specific surface area of 543 m(2) g(-1), a total pore volume of 0.677 cm(3) g(-1), and fairly small mesopores (approximate to 5.3 nm). The material was applied in a symmetric supercapacitor and exhibited a specific capacitance of 248 F g(-1) (0.12 F cm(-2)) at a constant current density of 0.1 Ag-1; thus suggesting that hollow carbon-MoS2 carbon nanoplates are promising candidate materials for supercapacitors.}, language = {en} } @article{NieuwenhuisZhongMetwallietal.2019, author = {Nieuwenhuis, Sophie and Zhong, Qi and Metwalli, Ezzeldin and Biessmann, Lorenz and Philipp, Martine and Miasnikova, Anna and Laschewsky, Andre and Papadakis, Christine M. and Cubitt, Robert and Wang, Jiping and M{\"u}ller-Buschbaum, Peter}, title = {Hydration and Dehydration Kinetics: Comparison between Poly(N-isopropyl methacrylamide) and Poly(methoxy diethylene glycol acrylate) Films}, series = {Langmuir}, volume = {35}, journal = {Langmuir}, number = {24}, publisher = {American Chemical Society}, address = {Washington}, issn = {0743-7463}, doi = {10.1021/acs.langmuir.9b00535}, pages = {7691 -- 7702}, year = {2019}, abstract = {Thermoresponsive films of poly(N-isopropyl methacrylamide) (PNIPMAM) and poly(methoxy diethylene glycol acrylate) (PMDEGA) are compared with respect to their hydration and dehydration kinetics using in situ neutron reflectivity. Both as-prepared films present a homogeneous single-layer structure and have similar transition temperatures of the lower critical solution temperature type (TT, PNIPMAM 38 degrees C and PMDEGA 41 degrees C). After hydration in unsaturated D2O vapor at 23 degrees C, a D2O enrichment layer is observed in PNIPMAM films adjacent to the Si substrate. In contrast, two enrichment layers are present in PMDEGA films (close to the vapor interface and the Si substrate). PNIPMAM films exhibit a higher hydration capability, ascribed to having both donor (N-H) and acceptor (C=O) units for hydrogen bonds. "While the swelling of the PMDEGA films is mainly caused by the increase of the enrichment layers, the thickness of the entire PNIPMAM films increases with time. The observed longer relaxation time for swelling of PNIPMAM films is attributed to the much higher glass transition temperature of PNIPMAM. When dehydrating both films by increasing the temperature above the TT, they react with a complex response consisting of three stages (shrinkage, rearrangement, and reswelling). PNIPMAM films respond faster than PMDEGA films. After dehydration, both films still contain a large amount of D2O, and no completely dry film state is reached for a temperature above their TTs.}, language = {en} } @article{AlrefaiMondalWrucketal.2019, author = {Alrefai, Anas and Mondal, Suvendu Sekhar and Wruck, Alexander and Kelling, Alexandra and Schilde, Uwe and Brandt, Philipp and Janiak, Christoph and Schoenfeld, Sophie and Weber, Birgit and Rybakowski, Lawrence and Herrman, Carmen and Brennenstuhl, Katlen and Eidner, Sascha and Kumke, Michael Uwe and Behrens, Karsten and G{\"u}nter, Christina and M{\"u}ller, Holger and Holdt, Hans-J{\"u}rgen}, title = {Hydrogen-bonded supramolecular metal-imidazolate frameworks: gas sorption, magnetic and UV/Vis spectroscopic properties}, series = {Journal of Inclusion Phenomena and Macrocyclic Chemistry}, volume = {94}, journal = {Journal of Inclusion Phenomena and Macrocyclic Chemistry}, number = {3-4}, publisher = {Springer}, address = {Dordrecht}, issn = {1388-3127}, doi = {10.1007/s10847-019-00926-6}, pages = {155 -- 165}, year = {2019}, abstract = {By varying reaction parameters for the syntheses of the hydrogen-bonded metal-imidazolate frameworks (HIF) HIF-1 and HIF-2 (featuring 14 Zn and 14 Co atoms, respectively) to increase their yields and crystallinity, we found that HIF-1 is generated in two different frameworks, named as HIF-1a and HIF-1b. HIF-1b is isostructural to HIF-2. We determined the gas sorption and magnetic properties of HIF-2. In comparison to HIF-1a (Brunauer-Emmett-Teller (BET) surface area of 471m(2) g(-1)), HIF-2 possesses overall very low gas sorption uptake capacities [BET(CO2) surface area=85m(2) g(-1)]. Variable temperature magnetic susceptibility measurement of HIF-2 showed antiferromagnetic exchange interactions between the cobalt(II) high-spin centres at lower temperature. Theoretical analysis by density functional theory confirmed this finding. The UV/Vis-reflection spectra of HIF-1 (mixture of HIF-1a and b), HIF-2 and HIF-3 (with 14 Cd atoms) were measured and showed a characteristic absorption band centered at 340nm, which was indicative for differences in the imidazolate framework.}, language = {en} } @article{BalkBehlLendlein2019, author = {Balk, Maria and Behl, Marc and Lendlein, Andreas}, title = {Hydrolytic Degradation of Actuators Based on Copolymer Networks From Oligo(epsilon-caprolactone) Dimethacrylate and n-Butyl Acrylate}, series = {MRS advances}, volume = {4}, journal = {MRS advances}, number = {21}, publisher = {Cambridge Univ. Press}, address = {New York}, issn = {2059-8521}, doi = {10.1557/adv.2019.202}, pages = {1193 -- 1205}, year = {2019}, abstract = {Shape-memory polymer actuators often contain crystallizable polyester segments. Here, the influence of accelerated hydrolytic degradation on the actuation performance in copolymer networks based on oligo(epsilon-caprolactone) dimethacrylate (OCL) and n-butyl acrylate is studied The semi-crystalline OCL was utilized as crosslinker with molecular weights of 2.3 and 15.2 kg.mol(-1) (ratio: 1:1 wt\%) and n-butyl acrylate (25 wt\% relative to OCL content) acted as softening agent creating the polymer main chain segments within the network architecture. The copolymer networks were programmed by 50\% elongation and were degraded by means of alkaline hydrolysis utilizing sodium hydroxide solution (pH = 13). Experiments were performed in the range of the broad melting range of the actuators at 40 degrees C. The degradation of test specimen was monitored by the sample mass, which was reduced by 25 wt\% within 105 d .45 degradation products, fragments of OCL with molecular masses ranging from 400 to 50.000 g.mol(-1) could be detected by NMR spectroscopy and GPC measurements. The cleavage of ester groups included in OCL segments resulted in a decrease of the melting temperature (T-m) related to the actuator domains (amorphous at the temperature of degradation) and simultaneously, the T-m associated to the skeleton domain was increased (semi-crystalline at the temperature of degradation). The alkaline hydrolysis decreased the polymer chain orientation of OCL domains until a random alignment of crystalline domains was obtained. This result was confirmed by cyclic thermomechanical actuation tests. The performance of directed movements decreased almost linearly as function of degradation time resulting in the loss of functionality when the orientation of polymer chains disappeared. Here, actuators were able to provide reversible movements until 91 d when the accelerated bulk degradation procedure using alkaline hydrolysis (pH = 13) was applied. Accordingly, a lifetime of more than one year can be guaranteed under physiological conditions (pH = 7.4) when, e.g., artificial muscles for biomimetic robots as potential application for these kind of shape-memory polymer actuators will be addressed.}, language = {en} } @article{MazurekBudzyńskaBehlRazzaqetal.2019, author = {Mazurek-Budzyńska, Magdalena and Behl, Marc and Razzaq, Muhammad Yasar and N{\"o}chel, Ulrich and Rokicki, Gabriel and Lendlein, Andreas}, title = {Hydrolytic stability of aliphatic poly(carbonate-urea-urethane)s: Influence of hydrocarbon chain length in soft segment}, series = {Polymer Degradation and Stability}, volume = {161}, journal = {Polymer Degradation and Stability}, publisher = {Elsevier}, address = {Oxford}, issn = {0141-3910}, pages = {283 -- 297}, year = {2019}, abstract = {Poly(carbonate-urethane)s (PCUs) exhibit improved resistance to hydrolytic degradation and in vivo stress cracking compared to poly(ester-urethane)s and their degradation leads to lower inflammation of the surrounding tissues. Therefore, PCUs are promising implant materials and are considered for devices such as artificial heart or spine implants. In this work, the hydrolytic stability of different poly(carbonate-urethane-urea)s (PCUUs) was studied under variation of the length of hydrocarbon chain (6, 9, 10, and 12 methylene units) between the carbonate linkages in the precursors. PCUUs were synthesized from isophorone diisocyanate and oligo(alkylene carbonate) diols using the moisture-cure method. The changes of sample weight, thermal and mechanical properties, morphology, as well as the degradation products after immersion in a buffer solution (PBS, pH = 7.4) for up to 10 weeks at 37 degrees C were monitored and analyzed. In addition, mechanical properties after 20 weeks (in PBS, 37 degrees C) were investigated. The gel content was determined based on swelling experiments in chloroform. Based on the DSC analysis, slight increases of melting transitions of PCUUs were observed, which were attributed to structure reorganization related to annealing at 37 degrees C rather than to the degradation of the PCUU. Tensile strength after 20 weeks of all investigated samples remained in the range of 29-39 MPa, whereas the elongation at break e(m) decreased only slightly and remained in the range between 670 and 800\%. Based on the characterization of degradation products after up to 10 weeks of immersion it was assessed that oligomers are mainly consisting of hard segments containing urea linkages, which could be assigned to hindered-urea dissociation mechanism. The investigations confirmed good resistance of PCUUs to hydrolysis. Only minor changes in the crystallinity, as well as thermal and mechanical properties were observed and depended on hydrocarbon chain length in soft segment of PCUUs. (C) 2019 Published by Elsevier Ltd.}, language = {en} } @article{GarakaniLiuGlebeetal.2019, author = {Garakani, Tayebeh Mirzaei and Liu, Zhanzhi and Glebe, Ulrich and Gehrmann, Julia and Lazar, Jaroslav and Mertens, Marie Anna Stephanie and M{\"o}ller, Mieke and Hamzelui, Niloofar and Zhu, Leilei and Schnakenberg, Uwe and B{\"o}ker, Alexander and Schwaneberg, Ulrich}, title = {In Situ Monitoring of Membrane Protein Insertion into Block Copolymer Vesicle Membranes and Their Spreading via Potential-Assisted Approach}, series = {ACS applied materials \& interfaces}, volume = {11}, journal = {ACS applied materials \& interfaces}, number = {32}, publisher = {American Chemical Society}, address = {Washington}, issn = {1944-8244}, doi = {10.1021/acsami.9b09302}, pages = {29276 -- 29289}, year = {2019}, abstract = {Synthosomes are polymer vesicles with trans membrane proteins incorporated into block copolymer membranes. They have been used for selective transport in or out of the vesicles as well as catalysis inside the compartments. However, both the insertion process of the membrane protein, forming nanopores, and the spreading of the vesicles on planar substrates to form solid-supported biomimetic membranes have been rarely studied yet. Herein, we address these two points and, first, shed light on the real-time monitoring of protein insertion via isothermal titration calorimetry. Second, the spreading process on different solid supports, namely, SiO2, glass, and gold, via different techniques like spin- and dip-coating as well as a completely new approach of potential-assisted spreading on gold surfaces was studied. While inhomogeneous layers occur via traditional methods, our proposed potential-assisted strategy to induce adsorption of positively charged vesicles by applying negative potential on the electrode leads to remarkable vesicle spreading and their further fusion to form more homogeneous planar copolymer films on gold. The polymer vesicles in our study are formed from amphiphilic copolymers poly(2-methyl oxazoline)-block-poly(dimethylsiloxane)-block-poly(2-methyl oxazoline) (PMOXA-b-PDMS-b-PMOXA). Engineered variants of the transmembrane protein ferric hydroxamate uptake protein component A (FhuA), one of the largest beta-barrel channel proteins, are used as model nanopores. The incorporation of FhuA Delta 1-160 is shown to facilitate the vesicle spreading process further. Moreover, high accessibility of cysteine inside the channel was proven by linkage of a fluorescent dye inside the engineered variant FhuA Delta CVFtev and hence preserved functionality of the channels after spreading. The porosity and functionality of the spread synthosomes on the gold plates have been examined by studying the passive ion transport response in the presence of Li+ and ClO4- ions and electrochemical impedance spectroscopy analysis. Our approach to form solid-supported biomimetic membranes via the potential-assisted strategy could be important for the development of new (bio-) sensors and membranes.}, language = {en} } @article{SchuckLehmannOllivieretal.2019, author = {Schuck, G{\"o}tz and Lehmann, Frederike and Ollivier, Jacques and Mutka, Hannu and Schorr, Susan}, title = {Influence of chloride substitution on the rotational dynamics of methylammonium in MAPbI(3-x)Cl(x) perovskites}, series = {The journal of physical chemistry : C, Nanomaterials and interfaces}, volume = {123}, journal = {The journal of physical chemistry : C, Nanomaterials and interfaces}, number = {18}, publisher = {American Chemical Society}, address = {Washington}, issn = {1932-7447}, doi = {10.1021/acs.jpcc.9b01238}, pages = {11436 -- 11446}, year = {2019}, abstract = {Hybrid halide perovskites, MAPbI(3), MAPbI(2.94)Cl(0.0)6, and MAPbCl(3) (MA, methylammonium), were investigated using inelastic and quasielastic neutron scattering (QENS) with the aim of elucidating the impact of chloride substitution on the rotational dynamics of MA. In this context, we discuss the influence of the inelastic neutron scattering caused by low-energy phonons on QENS, resulting from the MA rotational dynamics in MAPbI(3-x)Cl(x). Through a comparative temperature-dependent QENS investigation with different energy resolutions, which allow a wide Fourier time window, we achieved a consistent description of the influence of chlorine substitution in MAPbI(3) on the MA dynamics. Our results showed that chlorine substitution in the low-temperature orthorhombic phase leads to a weakening of the hydrogen bridge bonds, since the characteristic relaxation times of C-3 rotation at 70 K in MAPbCl(3) (135 ps) and MAPbI(2.94)Cl(0.06) (485 ps) are much shorter than that in MAPbI(3) (1635 ps). For the orthorhombic phase, we obtained the activitin energies from the temperature-dependent characteristic relaxation times tau (c3). by Arrhenius fits, indicating lower values of E-a for MAPbCl(3) and MAPbI(2.94)Cl(0.06) compared to that of MAPbI(3). We also performed QENS analyses at 190 K for all three samples. Here, we observed that MAPbCI(3) shows slower MA rotational dynamics than MAPbI(3) in the disordered structure.}, language = {en} } @article{MuellerFoerstendorfSteudtneretal.2019, author = {M{\"u}ller, Katharina and Foerstendorf, Harald and Steudtner, Robin and Tsushima, Satoru and Kumke, Michael Uwe and Lef{\`e}vre, Gr{\´e}gory and Rothe, J{\"o}rg and Mason, Harris and Szab{\´o}, Zolt{\´a}n and Yang, Ping and Adam, Christian K. R. and Andr{\´e}, R{\´e}mi and Brennenstuhl, Katlen and Chiorescu, Ion and Cho, Herman M. and Creff, Ga{\"e}lle and Coppin, Fr{\´e}d{\´e}ric and Dardenne, Kathy and Den Auwer, Christophe and Drobot, Bj{\"o}rn and Eidner, Sascha and Hess, Nancy J. and Kaden, Peter and Kremleva, Alena and Kretzschmar, Jerome and Kr{\"u}ger, Sven and Platts, James A. and Panak, Petra and Polly, Robert and Powell, Brian A. and Rabung, Thomas and Redon, Roland and Reiller, Pascal E. and R{\"o}sch, Notker and Rossberg, Andr{\´e} and Scheinost, Andreas C. and Schimmelpfennig, Bernd and Schreckenbach, Georg and Skerencak-Frech, Andrej and Sladkov, Vladimir and Solari, Pier Lorenzo and Wang, Zheming and Washton, Nancy M. and Zhang, Xiaobin}, title = {Interdisciplinary Round-Robin Test on molecular spectroscopy of the U(VI) Acetate System}, series = {ACS omega / American Chemical Society}, volume = {4}, journal = {ACS omega / American Chemical Society}, number = {5}, publisher = {American Chemical Society}, address = {Washington}, issn = {2470-1343}, doi = {10.1021/acsomega.9b00164}, pages = {8167 -- 8177}, year = {2019}, abstract = {A comprehensive molecular analysis of a simple aqueous complexing system. U(VI) acetate. selected to be independently investigated by various spectroscopic (vibrational, luminescence, X-ray absorption, and nuclear magnetic resonance spectroscopy) and quantum chemical methods was achieved by an international round-robin test (RRT). Twenty laboratories from six different countries with a focus on actinide or geochemical research participated and contributed to this scientific endeavor. The outcomes of this RRT were considered on two levels of complexity: first, within each technical discipline, conformities as well as discrepancies of the results and their sources were evaluated. The raw data from the different experimental approaches were found to be generally consistent. In particular, for complex setups such as accelerator-based X-ray absorption spectroscopy, the agreement between the raw data was high. By contrast, luminescence spectroscopic data turned out to be strongly related to the chosen acquisition parameters. Second, the potentials and limitations of coupling various spectroscopic and theoretical approaches for the comprehensive study of actinide molecular complexes were assessed. Previous spectroscopic data from the literature were revised and the benchmark data on the U(VI) acetate system provided an unambiguous molecular interpretation based on the correlation of spectroscopic and theoretical results. The multimethodologic approach and the conclusions drawn address not only important aspects of actinide spectroscopy but particularly general aspects of modern molecular analytical chemistry.}, language = {en} } @article{ZhangKochovskiLeeetal.2019, author = {Zhang, Su-Yun and Kochovski, Zdravko and Lee, Hui-Chun and Lu, Yan and Zhang, Hemin and Zhang, Jie and Sun, Jian-Ke and Yuan, Jiayin}, title = {Ionic organic cage-encapsulating phase-transferable metal clusters}, series = {Chemical science}, volume = {10}, journal = {Chemical science}, number = {5}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {2041-6520}, doi = {10.1039/c8sc04375b}, pages = {1450 -- 1456}, year = {2019}, abstract = {Exploration of metal clusters (MCs) adaptive to both aqueous and oil phases without disturbing their size is promising for a broad scope of applications. The state-of-the-art approach via ligand-binding may perturb MCs' size due to varied metal-ligand binding strength when shuttling between solvents of different polarity. Herein, we applied physical confinement of a series of small noble MCs (<1 nm) inside ionic organic cages (I-Cages), which by means of anion exchange enables reversible transfer of MCs between aqueous and hydrophobic solutions without varying their ultrasmall size. Moreover, the MCs@I-Cage hybrid serves as a recyclable, reaction-switchable catalyst featuring high activity in liquid-phase NH3BH3 (AB) hydrolysis reaction with a turnover frequency (TOF) of 115 min-1.}, language = {en} } @article{KleinpeterKoch2019, author = {Kleinpeter, Erich and Koch, Andreas}, title = {Is the term "Carbene" justified for remote N-heterocyclic carbenes (r-NHCs) and abnormal N-heterocyclic carbenes (aNHCs/MICs)?}, series = {Tetrahedron}, volume = {75}, journal = {Tetrahedron}, number = {11}, publisher = {Elsevier}, address = {Oxford}, issn = {0040-4020}, doi = {10.1016/j.tet.2019.02.005}, pages = {1548 -- 1554}, year = {2019}, abstract = {The spatial magnetic properties, through-space NMR shieldings (TSNMRS), of typical N-heterocyclic carbenes NHCs, r-NHCs, a-NHCs and MICs have been calculated using the GIAO perturbation method employing the nucleus independent chemical shift (NICS) concept and visualized as iso-chemical-shielding surfaces (ICSS) of various size and direction. Prior to that both structures and 13C chemical shifts were calculated and in case of isolated carbenes the computed δ(13C)/ppm values compared (as a quality criterion for obtained structures) with the experimental ones. The TSNMRS values of the studied carbenes, which are in mesomeric equilibrium with zwitterionic (ylide/betaine/mesoionic) resonance contributors, are employed to qualify and quantify the present electronic structure and if the term carbene is still justified to denote the compounds studied. The results, thus obtained from spatial magnetic properties (TSNMRS), are compared with the geometry of the compounds, the corresponding WIBERG's bond index values, and the 13C chemical shifts especially of the carbene electron-deficient centre.}, language = {en} } @article{RiemerShipmanWessigetal.2019, author = {Riemer, Nastja and Shipman, Michael and Wessig, Pablo and Schmidt, Bernd}, title = {Iterative arylation of itaconimides with diazonium salts through electrophilic palladium catalysis}, series = {The journal of organic chemistry}, volume = {84}, journal = {The journal of organic chemistry}, number = {9}, publisher = {American Chemical Society}, address = {Washington}, issn = {0022-3263}, doi = {10.1021/acs.joc.9b00627}, pages = {5732 -- 5746}, year = {2019}, abstract = {N-Arylitaconimides, accessible from maleic anhydride, anilines, and paraformaldehyde, react with arene diazonium salts in Pd-catalyzed Matsuda-Heck arylation to the pharmacologically relevant E-configured 3-arylmethylidene pyrrolidine-2,5-diones (also known as arylmethylidene succinimides) through exo-selective beta-H-elimination. The coupling proceeds at ambient temperature with the simple and easy-to-handle precatalyst Pd-II-acetate under ligandand base-free conditions. Notable features are high isolated yields, regio- and stereoselectivities, and short reaction times. In a comparative investigation, aryl iodides, bromides, and triflates were shown to be inferior coupling reagents in this reaction. The 3-arylmethylidene pyrrolidine-2,5-diones undergo second Matsuda-Heck coupling, which proceeds via endo-selective beta-H-elimination to give diarylmethyl-substituted maleimides as coupling products. These products can also be accessed in one flask by sequential addition of different arene diazonium salts to the starting itaconimide. The potential of 3-arylmethylidene succinimides as photoswitches was tested. Upon irradiation of the E-isomer at 300 nm, partial isomerization to the Z-isomer (E/Z = 65:35 in the photostationary state) was observed. The isomerization was found to be nearly completely reversible by irradiating the mixture at 400 nm.}, language = {en} } @article{BurekDenglerEmmerlingetal.2019, author = {Burek, Katja and Dengler, Joachim and Emmerling, Franziska and Feldmann, Ines and Kumke, Michael Uwe and Stroh, Julia}, title = {Lanthanide Luminescence Revealing the Phase Composition in Hydrating Cementitious Systems}, series = {ChemistryOpen}, volume = {8}, journal = {ChemistryOpen}, number = {12}, publisher = {Wiley-VCH-Verl.}, address = {Weinheim}, issn = {2191-1363}, doi = {10.1002/open.201900249}, pages = {1441 -- 1452}, year = {2019}, abstract = {The hydration process of Portland cement in a cementitious system is crucial for development of the high-quality cement-based construction material. Complementary experiments of X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) and time-resolved laser fluorescence spectroscopy (TRLFS) using europium (Eu(III)) as an optical probe are used to analyse the hydration process of two cement systems in the absence and presence of different organic admixtures. We show that different analysed admixtures and the used sulphate carriers in each cement system have a significant influence on the hydration process, namely on the time-dependence in the formation of different hydrate phases of cement. Moreover, the effect of a particular admixture is related to the type of sulphate carrier used. The quantitative information on the amounts of the crystalline cement paste components is accessible via XRD analysis. Distinctly different morphologies of ettringite and calcium-silicate-hydrates (C-S-H) determined by SEM allow visual conclusions about formation of these phases at particular ageing times. The TRLFS data provides information about the admixture influence on the course of the silicate reaction. The dip in the dependence of the luminescence decay times on the hydration time indicates the change in the structure of C-S-H in the early hydration period. Complementary information from XRD, SEM and TRLFS provides detailed information on distinct periods of the cement hydration process.}, language = {en} } @article{KopyshevKanevcheLomadzeetal.2019, author = {Kopyshev, Alexey and Kanevche, Katerina and Lomadze, Nino and Pfitzner, Emanuel and Loebner, Sarah and Patil, Rohan R. and Genzer, Jan and Heberle, Joachim and Santer, Svetlana}, title = {Light-Induced Structuring of Photosensitive Polymer Brushes}, series = {ACS Applied polymer materials}, volume = {1}, journal = {ACS Applied polymer materials}, number = {11}, publisher = {American Chemical Society}, address = {Washington}, issn = {2637-6105}, doi = {10.1021/acsapm.9b00705}, pages = {301 -- 3026}, year = {2019}, abstract = {We investigate light-induced irreversible structuring of surface topographies in poly(3-sulfopropyl methacrylate/potassium salt) (PSPMK) brushes on flat solid substrates prepared by surface-initiated atom transfer radical polymerization. The brushes have been loaded with azobenzene-based surfactant comprised of positively charged headgroups and hydrophobic tail. The surfactant exhibits photoresponsive properties through photoisomerization from the trans to cis states leading to significant changes in physicochemical properties of grafted polymer chains. The azobenzene surfactant enables photoresponsive behavior without introducing irreversible changes to chemical composition of the parent polymer brush. Exposing these photosensitive brushes to irradiation with UV interference beams causes the polymer brush to form surface relief grating (SRG) patterns. The cationic surfactant penetrates only similar to 25\% of the upper portion of the PSPMK brush, resulting in the formation of two sections within the brush: a photoresponsive upper layer and nonfunctional buried layer, which is not affected by the UV irradiation. Using nano-FTIR spectroscopy, we characterize locally the chemical composition of the polymer brush and confirm partial penetration of the surfactant within the film. Strong optomechanical stresses take place only within the upper layer of the brush that is impregnated with the surfactants and causes surface topography alternation due to a local rupture of grafted polymer chains. The cleaved polymer chains are then removed from the surface by using a good solvent, leaving behind topographical grating on top of the nonfunctional brush layer. We demonstrate that photostructured polymer brush can be used for reversible switching of brush topography by varying external humidity.}, language = {en} } @article{KocSchoenemannArnuthalingametal.2019, author = {Koc, Julian and Sch{\"o}nemann, Eric and Arnuthalingam, Ajitha and Clarke, Jessica L. and Finlay, John A. and Clare, Anthony S. and Laschewsky, Andre and Rosenhahn, Axel}, title = {Low-fouling thin hydrogel coatings made of photo-cross-linked polyzwitterions}, series = {Langmuir}, volume = {35}, journal = {Langmuir}, number = {5}, publisher = {American Chemical Society}, address = {Washington}, issn = {0743-7463}, doi = {10.1021/acs.langmuir.8b02799}, pages = {1552 -- 1562}, year = {2019}, abstract = {Although zwitterionic chemistries are among the most promising materials for producing nonfouling surfaces, their structural diversity has been low until now. Here, we compare the in vitro fouling behavior of a set of four systematically varied sulfa-/sulfobetaine-containing zwitterionic hydrogel coatings against a series of proteins and nonmotile as well as motile marine organisms as model foulers. The coatings are prepared by simultaneous photoinduced cross-linking and surface anchoring to elucidate the effect of the molecular structure of the zwitterionic moieties on their antifouling activity. Analogously prepared coatings of poly(butyl methacrylate) and poly(oligoethylene glycol methacrylate) serve as references. Photoreactive polymers are synthesized by the statistical copolymerization of sulfobetaine or sulfabetaine methacrylates and methacrylamides with a benzophenone derivative of 2-hydroxyethyl methacrylate and are applied as a thin film coating. While keeping the density of the zwitterionic and cross-linker groups constant, the molecular structure of the zwitterionic side chains is varied systematically, as is the arrangement of the ion pairs in the side chain by changing the classical linear geometry to a novel Y-shaped geometry. All of the polyzwitterions strongly reduce fouling compared to poly(butyl methacrylate). Overall, the sulfabetaine polyzwitterion coatings studied matches the high antifouling effectiveness of oligo(ethylene glycol)-based ones used as a control. Nevertheless, performances varied individually for a given pair of polymer and fouler. The case of the polysulfobetaines exemplifies that minor chemical changes in the polymer structure affect the antifouling performance markedly. Accordingly, the antifouling performance of such polymers cannot be correlated simply to the type of zwitterion used (which could be generally ranked as better performing or poorer performing) but is a result of the polymer's precise chemical structure. Our findings underline the need to enlarge the existing structural diversity of polyzwitterions for antifouling purposes to optimize the potential of their chemical structure.}, language = {en} } @article{RazzaqBehlLendlein2019, author = {Razzaq, Muhammad Yasar and Behl, Marc and Lendlein, Andreas}, title = {Magneto-Mechanical Actuators with Reversible Stretching and Torsional Actuation Capabilities}, series = {MRS Advances}, volume = {4}, journal = {MRS Advances}, number = {19}, publisher = {Cambridge Univ. Press}, address = {New York}, issn = {2059-8521}, doi = {10.1557/adv.2019.123}, pages = {1057 -- 1065}, year = {2019}, abstract = {Composite actuators consisting of magnetic nanoparticles dispersed in a crystallizable multiphase polymer system can be remotely controlled by alternating magnetic fields (AMF). These actuators contain spatially segregated crystalline domains with chemically different compositions. Here, the crystalline domain associated to low melting transition range is responsible for actuation while the crystalline domain associated to the higher melting transition range determines the geometry of the shape change. This paper reports magnetomechanical actuators which are based on a single crystalline domain of oligo(omega-pentadecalactone) (OPDL) along with covalently integrated iron(III) oxide nanoparticles (ioNPs). Different geometrical modes of actuation such as a reversible change in length or twisting were implemented by a magneto-mechanical programming procedure. For an individual actuation mode, the degree of actuation could be tailored by variation of the magnetic field strengths. This material design can be easily extended to other composites containing other magnetic nanoparticles, e.g. with a high magnetic susceptibility.}, language = {en} } @article{RazzaqBehlHeucheletal.2019, author = {Razzaq, Muhammad Yasar and Behl, Marc and Heuchel, Matthias and Lendlein, Andreas}, title = {Matching magnetic heating and thermal actuation for sequential coupling in hybrid composites by design}, series = {Macromolecular rapid communications}, volume = {41}, journal = {Macromolecular rapid communications}, number = {1}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1022-1336}, doi = {10.1002/marc.201900440}, pages = {7}, year = {2019}, abstract = {Sequentially coupling two material functions requires matching the output from the first with the input of the second function. Here, magnetic heating controls thermal actuation of a hybrid composite in a challenging system environment causing an elevated level of heat loss. The concept is a hierarchical design consisting of an inner actuator of nanocomposite material, which can be remotely heated by exposure to an alternating magnetic field (AMF) and outer layers of a porous composite system with a closed pore morphology. These porous layers act as heat insulators and as barriers to the surrounding water. By exposure to the AMF, a local bulk temperature of 71 degrees C enables the magnetic actuation of the device, while the temperature of the surrounding water is kept below 50 degrees C. Interestingly, the heat loss during magnetic heating leads to an increase of the water phase (small volume) temperature. The temperature increase is able to sequentially trigger an adjacent thermal actuator attached to the actuator composite. In this way it could be demonstrated how the AMF is able to initiate two kinds of independent actuations, which might be interesting for robotics operating in aqueous environments.}, language = {en} } @article{OtteSchmidt2019, author = {Otte, Fabian and Schmidt, Bernd}, title = {Matsuda-Heck Arylation of Glycals for the Stereoselective Synthesis of Aryl C-Glycosides}, series = {The journal of organic chemistry}, volume = {84}, journal = {The journal of organic chemistry}, number = {22}, publisher = {American Chemical Society}, address = {Washington}, issn = {0022-3263}, doi = {10.1021/acs.joc.9b02410}, pages = {14816 -- 14829}, year = {2019}, abstract = {The methoxymethyl-protected glycal L-amicetal, synthesized de novo from L-ethyl lactate through tandem ring-closing metathesis-isomerization sequence, undergoes a highly trans-diastereoselective Heck-type coupling reaction with various arene diazonium salts to furnish 2,3-unsaturated aryl C-glycosides in moderate to excellent yields. The products can be further functionalized, e.g., by hydrogenation, epoxidation, or dihydroxylation to furnish 2,3,6-tridesoxy, 2,3-anhydro-6-desoxy, or 6-desoxy aryl C-glycosides, respectively. The method was applied to the synthesis of an a-configured 6-desoxy-gliflozin derivative.}, language = {en} } @article{GuRisseLuetal.2019, author = {Gu, Sasa and Risse, Sebastian and Lu, Yan and Ballauff, Matthias}, title = {Mechanism of the oxidation of 3,3′,5,5′-tetramethylbenzidine catalyzed by peroxidase-like Pt nanoparticles immobilized in spherical polyelectrolyte brushes}, series = {ChemPhysChem}, volume = {21}, journal = {ChemPhysChem}, number = {5}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1439-4235}, doi = {10.1002/cphc.201901087}, pages = {450 -- 458}, year = {2019}, abstract = {Experimental and kinetic modelling studies are presented to investigate the mechanism of 3,3 ',5,5 '-tetramethylbenzidine (TMB) oxidation by hydrogen peroxide (H2O2) catalyzed by peroxidase-like Pt nanoparticles immobilized in spherical polyelectrolyte brushes (SPB-Pt). Due to the high stability of SPB-Pt colloidal, this reaction can be monitored precisely in situ by UV/VIS spectroscopy. The time-dependent concentration of the blue-colored oxidation product of TMB expressed by different kinetic models was used to simulate the experimental data by a genetic fitting algorithm. After falsifying the models with abundant experimental data, it is found that both H2O2 and TMB adsorb on the surface of Pt nanoparticles to react, indicating that the reaction follows the Langmuir-Hinshelwood mechanism. A true rate constant k, characterizing the rate-determining step of the reaction and which is independent on the amount of catalysts used, is obtained for the first time. Furthermore, it is found that the product adsorbes strongly on the surface of nanoparticles, thus inhibiting the reaction. The entire analysis provides a new perspective to study the catalytic mechanism and evaluate the catalytic activity of the peroxidase-like nanoparticles.}, language = {en} } @article{SardarianInalooModarresiAlametal.2019, author = {Sardarian, Ali Reza and Inaloo, Iman Dindarloo and Modarresi-Alam, Ali Reza and Kleinpeter, Erich and Schilde, Uwe}, title = {Metal-Free Regioselective Monocyanation of Hydroxy-, Alkoxy-, and Benzyloxyarenes by Potassium Thiocyanate and Silica Sulfuric Acid as a Cyanating Agent}, series = {The journal of organic chemistry}, volume = {84}, journal = {The journal of organic chemistry}, number = {4}, publisher = {American Chemical Society}, address = {Washington}, issn = {0022-3263}, doi = {10.1021/acs.joc.8b02191}, pages = {1748 -- 1756}, year = {2019}, abstract = {A novel and efficient metal- and solvent-free regioselective para-C-H cyanation of hydroxy-, alkoxy-, and benzyloxyarene derivatives has been introduced, using nontoxic potassium thiocyanate as a cyanating reagent in the presence of silica sulfuric acid (SSA). The desired products are obtained in good to high yields without any toxic byproducts.}, language = {en} } @article{HwangWalczakOschatzetal.2019, author = {Hwang, Jongkook and Walczak, Ralf and Oschatz, Martin and Tarakina, Nadezda and Schmidt, Bernhard V. K. J.}, title = {Micro-Blooming: Hierarchically Porous Nitrogen-Doped Carbon Flowers Derived from Metal-Organic Mesocrystals}, series = {Small}, volume = {15}, journal = {Small}, number = {37}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1613-6810}, doi = {10.1002/smll.201901986}, pages = {10}, year = {2019}, abstract = {Synthesis of 3D flower-like zinc-nitrilotriacetic acid (ZnNTA) mesocrystals and their conformal transformation to hierarchically porous N-doped carbon superstructures is reported. During the solvothermal reaction, 2D nanosheet primary building blocks undergo oriented attachment and mesoscale assembly forming stacked layers. The secondary nucleation and growth preferentially occurs at the edges and defects of the layers, leading to formation of 3D flower-like mesocrystals comprised of interconnected 2D micropetals. By simply varying the pyrolysis temperature (550-1000 degrees C) and the removal method of in the situ-generated Zn species, nonporous parent mesocrystals are transformed to hierarchically porous carbon flowers with controllable surface area (970-1605 m(2) g(-1)), nitrogen content (3.4-14.1 at\%), pore volume (0.95-2.19 cm(3) g(-1)), as well as pore diameter and structures. The carbon flowers prepared at 550 degrees C show high CO2/N-2 selectivity due to the high nitrogen content and the large fraction of (ultra)micropores, which can greatly increase the CO2 affinity. The results show that the physicochemical properties of carbons are highly dependent on the thermal transformation and associated pore formation process, rather than directly inherited from parent precursors. The present strategy demonstrates metal-organic mesocrystals as a facile and versatile means toward 3D hierarchical carbon superstructures that are attractive for a number of potential applications.}, language = {en} } @article{FriessWischkeLendlein2019, author = {Friess, Fabian and Wischke, Christian and Lendlein, Andreas}, title = {Microscopic analysis of shape-shiftable oligo(epsilon-caprolactone)-based particles}, series = {MRS advances}, volume = {4}, journal = {MRS advances}, number = {59-60}, publisher = {Cambridge Univ. Press}, address = {New York}, issn = {2059-8521}, doi = {10.1557/adv.2019.392}, pages = {3199 -- 3206}, year = {2019}, abstract = {Spherical particles are routinely monitored and described by hydrodynamic diameters determined, e.g., by light scattering techniques. Non-spherical particles such as prolate ellipsoids require alternative techniques to characterize particle size as well as particle shape. In this study, oligo(epsilon-caprolactone) (oCL) based micronetwork (MN) particles with a shape-shifting function based on their shape-memory capability were programmed from spherical to prolate ellipsoidal shape aided by incorporation and stretching in a water-soluble phantom matrix. By applying light microscopy with automated contour detection and aspect ratio analysis, differences in characteristic aspect ratio distributions of non-crosslinked microparticles (MPs) and crosslinked MNs were detected when the degrees of phantom elongation (30-290\%) are increased. The thermally induced shape recovery of programmed MNs starts in the body rather than from the tips of ellipsoids, which may be explained based on local differences in micronetwork deformation. By this approach, fascinating intermediate particle shapes with round bodies and two opposite sharp tips can be obtained, which could be of interest, e.g., in valves or other technical devices, in which the tips allow to temporarily encage the switchable particle in the desired position.}, language = {en} } @article{WangXuLietal.2019, author = {Wang, Weiwei and Xu, Xun and Li, Zhengdong and Kratz, Karl and Ma, Nan and Lendlein, Andreas}, title = {Modulating human mesenchymal stem cells using poly(n-butyl acrylate) networks in vitro with elasticity matching human arteries}, series = {Clinical hemorheology and microcirculation : blood flow and vessels}, volume = {71}, journal = {Clinical hemorheology and microcirculation : blood flow and vessels}, number = {2}, publisher = {IOS Press}, address = {Amsterdam}, issn = {1386-0291}, doi = {10.3233/CH-189418}, pages = {277 -- 289}, year = {2019}, abstract = {Non-swelling hydrophobic poly(n-butyl acrylate) network (cPnBA) is a candidate material for synthetic vascular grafts owing to its low toxicity and tailorable mechanical properties. Mesenchymal stem cells (MSCs) are an attractive cell type for accelerating endothelialization because of their superior anti-thrombosis and immune modulatory function. Further, they can differentiate into smooth muscle cells or endothelial-like cells and secret pro-angiogenic factors such as vascular endothelial growth factor (VEGF). MSCs are sensitive to the substrate mechanical properties, with the alteration of their major cellular behavior and functions as a response to substrate elasticity. Here, we cultured human adipose-derived mesenchymal stem cells (hADSCs) on cPnBAs with different mechanical properties (cPnBA250, Young's modulus (E) = 250 kPa; cPnBA1100, E = 1100 kPa) matching the elasticity of native arteries, and investigated their cellular response to the materials including cell attachment, proliferation, viability, apoptosis, senescence and secretion. The cPnBA allowed high cell attachment and showed negligible cytotoxicity. F-actin assembly of hADSCs decreased on cPnBA films compared to classical tissue culture plate. The difference of cPnBA elasticity did not show dramatic effects on cell attachment, morphology, cytoskeleton assembly, apoptosis and senescence. Cells on cPnBA250, with lower proliferation rate, had significantly higher VEGF secretion activity. These results demonstrated that tuning polymer elasticity to regulate human stem cells might be a potential strategy for constructing stem cell-based artificial blood vessels.}, language = {en} } @article{LaschewskyRosenhahn2019, author = {Laschewsky, Andr{\´e} and Rosenhahn, Axel}, title = {Molecular design of zwitterionic polymer interfaces}, series = {Langmuir}, volume = {35}, journal = {Langmuir}, number = {5}, publisher = {American Chemical Society}, address = {Washington}, issn = {0743-7463}, doi = {10.1021/acs.langmuir.8b01789}, pages = {1056 -- 1071}, year = {2019}, abstract = {The widespread occurrence of zwitterionic compounds in nature has incited their frequent use in designing biomimetic materials. Therefore, zwitterionic polymers are a thriving field. A particular interest for this particular polymer class has currently focused on their use in establishing neutral, low-fouling surfaces. After highlighting strategies to prepare model zwitterionic surfaces as well as those that are more suitable for practical purposes relying strongly on radical polymerization methods, we present recent efforts to diversify the structure of the hitherto quite limited variety of zwitterionic monomers and of the derived polymers. We identify key structural variables, consider their influence on essential properties such as overall hydrophilicity and long-term stability, and discuss promising targets for the synthesis of new variants.}, language = {en} } @article{MehrGrigorievPuretskiyetal.2019, author = {Mehr, Fatemeh Naderi and Grigoriev, Dmitry and Puretskiy, Nikolay and B{\"o}ker, Alexander}, title = {Mono-patchy zwitterionic microcolloids as building blocks for pH-controlled self-assembly}, series = {Soft matter}, volume = {15}, journal = {Soft matter}, number = {11}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1744-683X}, doi = {10.1039/c8sm02151a}, pages = {2430 -- 2438}, year = {2019}, abstract = {A directional molecular interaction between microcolloids can be achieved through pre-defined sites on their surface, patches, which might make them follow each other in a controlled way and assemble into target structures of more complexity. In this article, we report the successful generation and characterization of mono-patchy melamine-formaldehyde microparticles with oppositely charged patches made of poly(methyl vinyl ether-alt-maleic acid) or polyethyleneimine via microcontact printing. The study of their self-aggregation behavior in solution shows that by change of pH, particle dimers are formed via attractive electrostatic force between the patchy and non-patchy surface of the particles, which reaches its optimum at a specific pH.}, language = {en} } @article{BuecheleChaoOstermannetal.2019, author = {B{\"u}chele, Dominique and Chao, Madlen and Ostermann, Markus and Leenen, Matthias and Bald, Ilko}, title = {Multivariate chemometrics as a key tool for prediction of K and Fe in a diverse German agricultural soil-set using EDXRF}, series = {Scientific Reports}, volume = {9}, journal = {Scientific Reports}, publisher = {Macmillan Publishers Limited, part of Springer Nature}, address = {London}, issn = {2045-2322}, doi = {10.1038/s41598-019-53426-5}, pages = {11}, year = {2019}, abstract = {Within the framework of precision agriculture, the determination of various soil properties is moving into focus, especially the demand for sensors suitable for in-situ measurements. Energy-dispersive X-ray fluorescence (EDXRF) can be a powerful tool for this purpose. In this study a huge diverse soil set (n = 598) from 12 different study sites in Germany was analysed with EDXRF. First, a principal component analysis (PCA) was performed to identify possible similarities among the sample set. Clustering was observed within the four texture classes clay, loam, silt and sand, as clay samples contain high and sandy soils low iron mass fractions. Furthermore, the potential of uni- and multivariate data evaluation with partial least squares regression (PLSR) was assessed for accurate determination of nutrients in German agricultural samples using two calibration sample sets. Potassium and iron were chosen for testing the performance of both models. Prediction of these nutrients in 598 German soil samples with EDXRF was more accurate using PLSR which is confirmed by a better overall averaged deviation and PLSR should therefore be preferred.}, language = {en} } @article{SchwarzeRiemerMuelleretal.2019, author = {Schwarze, Thomas and Riemer, Janine and M{\"u}ller, Holger and John, Leonard and Holdt, Hans-J{\"u}rgen and Wessig, Pablo}, title = {Na+ Selective Fluorescent Tools Based on Fluorescence Intensity Enhancements, Lifetime Changes, and on a Ratiometric Response}, series = {Chemistry - a European journal}, volume = {25}, journal = {Chemistry - a European journal}, number = {53}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {0947-6539}, doi = {10.1002/chem.201902536}, pages = {12412 -- 12422}, year = {2019}, abstract = {Over the years, we developed highly selective fluorescent probes for K+ in water, which show K+-induced fluorescence intensity enhancements, lifetime changes, or a ratiometric behavior at two emission wavelengths (cf. Scheme 1, K1-K4). In this paper, we introduce selective fluorescent probes for Na+ in water, which also show Na+ induced signal changes, which are analyzed by diverse fluorescence techniques. Initially, we synthesized the fluorescent probes 2, 4, 5, 6 and 10 for a fluorescence analysis by intensity enhancements at one wavelength by varying the Na+ responsive ionophore unit and the fluorophore moiety to adjust different K-d values for an intra- or extracellular Na+ analysis. Thus, we found that 2, 4 and 5 are Na+ selective fluorescent tools, which are able to measure physiologically important Na+ levels at wavelengths higher than 500 nm. Secondly, we developed the fluorescent probes 7 and 8 to analyze precise Na+ levels by fluorescence lifetime changes. Herein, only 8 (K-d=106 mm) is a capable fluorescent tool to measure Na+ levels in blood samples by lifetime changes. Finally, the fluorescent probe 9 was designed to show a Na+ induced ratiometric fluorescence behavior at two emission wavelengths. As desired, 9 (K-d=78 mm) showed a ratiometric fluorescence response towards Na+ ions and is a suitable tool to measure physiologically relevant Na+ levels by the intensity change of two emission wavelengths at 404 nm and 492 nm.}, language = {en} } @article{UnuabonahNoeskeWeberetal.2019, author = {Unuabonah, Emmanuel and N{\"o}ske, Robert and Weber, Jens and G{\"u}nter, Christina and Taubert, Andreas}, title = {New micro/mesoporous nanocomposite material from low-cost sources for the efficient removal of aromatic and pathogenic pollutants from water}, series = {Beilstein journal of nanotechnology}, volume = {10}, journal = {Beilstein journal of nanotechnology}, publisher = {Beilstein-Institut zur F{\"o}rderung der Chemischen Wissenschaften}, address = {Frankfurt, Main}, issn = {2190-4286}, doi = {10.3762/bjnano.10.11}, pages = {119 -- 131}, year = {2019}, abstract = {A new micro/mesoporous hybrid clay nanocomposite prepared from kaolinite clay, Carica papaya seeds, and ZnCl2 via calcination in an inert atmosphere is presented. Regardless of the synthesis temperature, the specific surface area of the nanocomposite material is between approximate to 150 and 300 m(2)/g. The material contains both micro- and mesopores in roughly equal amounts. X-ray diffraction, infrared spectroscopy, and solid-state nuclear magnetic resonance spectroscopy suggest the formation of several new bonds in the materials upon reaction of the precursors, thus confirming the formation of a new hybrid material. Thermogravimetric analysis/differential thermal analysis and elemental analysis confirm the presence of carbonaceous matter. The new composite is stable up to 900 degrees C and is an efficient adsorbent for the removal of a water micropollutant, 4-nitrophenol, and a pathogen, E. coli, from an aqueous medium, suggesting applications in water remediation are feasible.}, language = {en} } @article{ZhangGuoTangetal.2019, author = {Zhang, Su-Yun and Guo, Wen-Bin and Tang, Ying-Ying and Xu, Jin-Qiu and He, Zhang-Zhen}, title = {Observation of Spin Relaxation in a Vanadate Chloride with Quasi-One-Dimensional Linear Chain}, series = {Crystal growth \& design : integrating the fields of crystal engineering and crystal growth for the synthesis and applications of new materials}, volume = {19}, journal = {Crystal growth \& design : integrating the fields of crystal engineering and crystal growth for the synthesis and applications of new materials}, number = {4}, publisher = {American Chemical Society}, address = {Washington}, issn = {1528-7483}, doi = {10.1021/acs.cgd.8b01839}, pages = {2228 -- 2234}, year = {2019}, abstract = {A new cobalt(II) vanadate chloride, Pb2Co(OH)(V2O7)Cl, has been synthesized under mild hydrothermal conditions. It contains quasi-one-dimensional (1D) linear chains built by edge-sharing of (CoO6)-O-II octahedra. The cobalt(II) oxide chains are further interconnected by (V2O7)(4-) dimers into a three-dimensional (3D) anionic framework with Pb2+ and Cl- ions residing in Co4V8 12-member ring tunnels. The intrachain Co center dot center dot center dot Co distance is 3.041 angstrom, while the interchain distances are 8.742 and 9.256 angstrom. Magnetic measurements suggest the ferromagnetic intrachain and the antiferromagnetic interchain interactions with a specific value of J(intra)/J(inter) = 1.7 x 10(3). Zero-field heat capacity demonstrates the magnetic long-range ordering at 5.5 K. Alternating current (AC) magnetic susceptibility under zero external direct current (DC) fields displays two slow magnetic relaxations at low temperatures, giving characteristic relaxations (tau(0)) of 1.2(3) x 10(-12) and 1.9(4) x 10(-10) s with effective energy barriers (Delta(r)) of 76.1(2) and 48.4(5) K. The energy barrier between the spin up and spin-down states can be ascribed to the ferromagnetic spin chain and the Ising-like magnetic anisotropy in Pb2Co(OH)(V2O7)Cl.}, language = {en} } @article{BrunacciNeffeWischkeetal.2019, author = {Brunacci, Nadia and Neffe, Axel T. and Wischke, Christian and Naolou, Toufik and N{\"o}chel, Ulrich and Lendlein, Andreas}, title = {Oligodepsipeptide (nano)carriers}, series = {Journal of controlled release}, volume = {301}, journal = {Journal of controlled release}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0168-3659}, doi = {10.1016/j.jconrel.2019.03.004}, pages = {146 -- 156}, year = {2019}, abstract = {High drug loads of nanoparticles are essential to efficiently provide a desired dosage in the required timeframe, however, these conditions may not be reached with so far established degradable matrices. Our conceptual approach for increasing the drug load is based on strengthening the affinity between drug and matrix in combination with stabilizing drug-matrix-hybrids through strong intermolecular matrix interactions. Here, a method for designing such complex drug-matrix hybrids is introduced employing computational methods (molecular dynamics and docking) as well as experimental studies (affinity, drug loading and distribution, drug release from films and nanoparticles). As model system, dexamethasone (DXM), relevant for the treatment of inflammatory diseases, in combination with poly[(rac-lactide)-co-glycolide] (PLGA) as standard degradable matrix or oligo[(3-(S)-sec-butyl) morpholine-2,5-dione] diol (OBMD) as matrix with hypothesized stronger interaction with DXM were investigated. Docking studies predicted higher affinity of DXM to OBMD than PLGA and displayed amide bond participation in hydrogen bonding with OBMD. Experimental investigations on films and nanoparticles, i.e. matrices of different shapes and sizes, confirmed this phenomenon as shown e.g. by a similar to 10 times higher solid state solubility of DXM in OBMD than in PLGA. DXM-loaded particles of similar to 150 nm prepared by nanoprecipitation in aqueous environment had a drug loading (DL) up to 16 times higher when employing OBMD as matrix compared to PLGA carriers due to enhanced drug retention in the OBMD phase. Importantly, drug relase periods were not altered as the release from films and particles was mainly ruled by the diffusion length as well as matrix degradation rather than the matrix type, which can be assigned to water diffusing into the matrix and breaking up of drug-matrix hydrogen bonds. Overall, the presented design and fabrication scheme showed predictive power and might universally enable the screening of drug/matrix interactions particularly to expand the oligodepsipeptide platform technology, e.g. by varying the depsipeptide side chains, for drug carrier and release systems.}, language = {en} } @article{BalderasValadezSchuermannPacholski2019, author = {Balderas-Valadez, Ruth Fabiola and Sch{\"u}rmann, Robin Mathis and Pacholski, Claudia}, title = {One Spot-Two Sensors: Porous Silicon Interferometers in Combination With Gold Nanostructures Showing Localized Surface Plasmon Resonance}, series = {Frontiers in chemistry}, volume = {7}, journal = {Frontiers in chemistry}, publisher = {Frontiers Research Foundation}, address = {Lausanne}, issn = {2296-2646}, doi = {10.3389/fchem.2019.00593}, pages = {12}, year = {2019}, abstract = {Sensors composed of a porous silicon monolayer covered with a film of nanostructured gold layer, which provide two optical signal transduction methods, are fabricated and thoroughly characterized concerning their sensing performance. For this purpose, silicon substrates were electrochemically etched in order to obtain porous silicon monolayers, which were subsequently immersed in gold salt solution facilitating the formation of a porous gold nanoparticle layer on top of the porous silicon. The deposition process was monitored by reflectance spectroscopy, and the appearance of a dip in the interference pattern of the porous silicon layer was observed. This dip can be assigned to the absorption of light by the deposited gold nanostructures leading to localized surface plasmon resonance. The bulk sensitivity of these sensors was determined by recording reflectance spectra in media having different refractive indices and compared to sensors exclusively based on porous silicon or gold nanostructures. A thorough analysis of resulting shifts of the different optical signals in the reflectance spectra on the wavelength scale indicated that the optical response of the porous silicon sensor is not influenced by the presence of a gold nanostructure on top. Moreover, the adsorption of thiol-terminated polystyrene to the sensor surface was solely detected by changes in the position of the dip in the reflectance spectrum, which is assigned to localized surface plasmon resonance in the gold nanostructures. The interference pattern resulting from the porous silicon layer is not shifted to longer wavelengths by the adsorption indicating the independence of the optical response of the two nanostructures, namely porous silicon and nanostructured gold layer, to refractive index changes and pointing to the successful realization of two sensors in one spot.}, language = {en} } @article{MameriKoutchoukaliKoutchoukalietal.2019, author = {Mameri, Fatima and Koutchoukali, Ouahiba and Koutchoukali, Mohamed Salah and Hartwig, Anne and Nemdili, Leila and Ulrich, Joachim}, title = {Optimum operating conditions for manufacturing ibuprofen tablets coated with polyethylene glycol by melt crystallization process}, series = {Journal of Thermal Analysis and Calorimetry}, volume = {136}, journal = {Journal of Thermal Analysis and Calorimetry}, number = {2}, publisher = {Springer}, address = {Dordrecht}, issn = {1388-6150}, doi = {10.1007/s10973-018-7667-z}, pages = {833 -- 842}, year = {2019}, abstract = {The aim of this work is to apply the melt crystallization technology to manufacture ibuprofen tablets coated with polyethylene glycol in a single step. This technology, based on a pastillation process, allows in situ separation between two components (active ingredient and coating material). The design and application of this technique depend on the thermo-physical properties of the substances used, as well as on the existence of a eutectic point in the phase diagram. To evaluate the prerequisite conditions, first, DSC curves, allowing the construction of the phase diagram of the binary system, were investigated and the eutectic point was determined (30 mass\% ibuprofen, 52 degrees C). Then, the stability of the selected mixture (10:90 mass\% of ibuprofen, PEG6000) was studied by thermogravimetric analysis. Finally, the coating quality was investigated under different operating conditions including viscosity, cooling plate temperature, the power of ultrasound and seeding. This parametric study showed that seeding with PEG6000 is necessary to obtain a hemispherical pastille shape, a suitable separation and a pure and thick coating layer. In addition to the optimization of operating conditions of the in situ coating process, it was possible to determine the optimum viscosity and the cooling plate temperature (271.77 m Pa s, 25 degrees C) to obtain a uniform and crystalline coating. During the deposition of molten drops on the cooled surface, the progression of crystal growth was monitored online by optical microscopy. According to the good separation achieved and to the purity and thickness of the microscopic cross-sectional material, the in situ coating process is conceivable for the production of PEG6000-coated ibuprofen tablets.}, language = {en} } @article{SzatmariBelasriHeydenreichetal.2019, author = {Szatmari, Istvan and Belasri, Khadija and Heydenreich, Matthias and Koch, Andreas and Kleinpeter, Erich and Fulop, Ferenc}, title = {Ortho-Quinone methide driven synthesis of new O,N- or N,N-Heterocycles}, series = {ChemistryOpen : including thesis treasury}, volume = {8}, journal = {ChemistryOpen : including thesis treasury}, number = {7}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {2191-1363}, doi = {10.1002/open.201900150}, pages = {961 -- 971}, year = {2019}, abstract = {To synthesize functionalized Mannich bases that can serve two different types of ortho-quinone methide (o-QM) intermediates, 2-naphthol and 6-hydroxyquinoline were reacted with salicylic aldehyde in the presence of morpholine. The Mannich bases that can form o-QM and aza-o-QM were also synthesized by mixing 2-naphthol, 2-nitrobenzaldehyde, and morpholine followed by reduction of the nitro group. The highly functionalized aminonaphthol derivatives were then tested in [4+2] cycloaddition with different cyclic imines. The reaction proved to be both regio- and diastereoselective. In all cases, only one reaction product was obtained. Detailed structural analyses of the new polyheterocycles as well as conformational studies including DFT modelling were performed. The relative stability of o-QMs/aza-o-QM were also calculated, and the regioselectivity of the reactions could be explained only when the cycloaddition started from aminodiol 4. It was summarized that starting from diaminonaphthol 25, the regioselectivity of the reaction is driven by the higher nucleophilicity of the amino group compared with the hydroxy group. 12H-benzo[a]xanthen-12-one (11), formed via o-QM formation, was isolated as a side product. The proton NMR spectrum of 11 proved to be very unique from NMR point of view. The reason for the extreme low-field position of proton H-1 could be accounted for by theoretical calculation of structure and spatial magnetic properties of the compound in combination of ring current effects of the aromatic moieties and steric compression within the heavily hindered H(1)-C(1)-C(12b)-C(12a)-C(12)=O structural fragment.}, language = {en} } @article{LaiFengHeiletal.2019, author = {Lai, Feili and Feng, Jianrui and Heil, Tobias and Tian, Zhihong and Schmidt, Johannes and Wang, Gui-Chang and Oschatz, Martin}, title = {Partially delocalized charge in Fe-doped NiCo2S4 nanosheet-mesoporous carbon-composites for high-voltage supercapacitors}, series = {Journal of materials chemistry : A, Materials for energy and sustainability}, volume = {7}, journal = {Journal of materials chemistry : A, Materials for energy and sustainability}, number = {33}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {2050-7488}, doi = {10.1039/c9ta06250e}, pages = {19342 -- 19347}, year = {2019}, abstract = {Unraveling the effect of transition-metal doping on the energy storage properties of bimetallic sulfides remains a grand challenge. Herein, we construct bimetallic sulfide nanosheets and hence deliberately introduce transition-metal doping domains on their surface. The resulting materials show not only an enhanced density of states near the Fermi level but also partially delocalized charge as shown by density functional theory (DFT) calculations. Fe-doped NiCo2S4 nanosheets wrapped on N,S-doped ordered mesoporous carbon (Fe-NiCo2S4@N,S-CMK-3) are prepared, which show an enhanced specific capacitance of 197.8 F g(-1) in ionic liquid-based supercapacitors at a scan rate of 2 mV s(-1). This is significantly higher as compared to the capacitance of 155.2 and 135.9 F g(-1) of non-iron-doped NiCo2S4@N,S-CMK and Fe-NiCo2S4@CMK-3 electrodes, respectively. This result arises from the enhanced ionic liquid polarization effect and transportation ability from the Fe-NiCo2S4 surface and N,S-CMK-3 structure. Furthermore, the importance of matching multi-dimensional structures and ionic liquid ion sizes in the fabrication of asymmetric supercapacitors (ASCs) is demonstrated. As a result, the ASC device exhibits a high energy density of 107.5 W h kg(-1) at a power density of 100 W kg(-1) in a working-voltage window of 4 V when using Fe-NiCo2S4@N,S-CMK-3 and N,S-CMK-3 as positive and negative electrodes, respectively. This work puts forward a new direction to design supercapacitor composite electrodes for efficient ionic liquid coupling.}, language = {en} } @article{PrellerRungeBorchertZellmeretal.2019, author = {Preller, Tobias and Runge-Borchert, Gundula and Zellmer, Sabrina and Menzel, Dirk and Saein, Saeid Azimi and Peters, Jan and Raatz, Annika and Tiersch, Brigitte and Koetz, Joachim and Garnweitner, Georg}, title = {Particle-reinforced and functionalized hydrogels for SpineMan, a soft robotics application}, series = {Journal of materials science}, volume = {54}, journal = {Journal of materials science}, number = {5}, publisher = {Springer}, address = {New York}, issn = {0022-2461}, doi = {10.1007/s10853-018-3106-6}, pages = {4444 -- 4456}, year = {2019}, abstract = {SpineMan is designed as a prototype of a soft robotic manipulator that is constructed of alternating hard and soft segments similar to the human spine. Implementing such soft segments allows to surpass the rigidity of conventional robots and ensures safer workspaces where humans and machines can work side by side with less stringent safety restrictions. Therefore, we used a hydrogel as viscoelastic material consisting of poly(vinyl alcohol) and borax. The mechanical properties of the hydrogel were tailored by embedding silica particles of various particles sizes as well as in different mass fractions. Increased mass contents as well as larger particle sizes led to strongly enhanced rigidity with a more than doubled storage modulus of the composite compared to the pure hydrogel. Furthermore, specific functionalities were induced by the incorporation of superparamagnetic Fe3O4 nanoparticles that can in principle be used for sensing robotic motion and detecting malfunctions. Therefore, we precisely adjusted the saturation magnetization of the soft segments using defined mass contents of the nanoparticles. To ensure long-time shape stability and prevention of atmospheric influences on the prepared composites, a silicone skin of specific shore hardness was used. The composites and the soft segments were characterized by oscillation measurements, cryo-SEM, bending tests and SQUID measurements, which give insights into the properties in the passive and in the moving state of SpineMan. The utilization of tailored composites led to highly flexible, reinforced and functional soft segments, which ensure stability, easy movability by springs of the shape memory alloy nitinol and prevention of total failure.}, language = {en} } @article{FriessRochSeifertetal.2019, author = {Friess, Fabian and Roch, Toralf and Seifert, Barbara and Lendlein, Andreas and Wischke, Christian}, title = {Phagocytosis of spherical and ellipsoidal micronetwork colloids from crosslinked poly(epsilon-caprolactone)}, series = {International Journal of Pharmaceutics}, volume = {567}, journal = {International Journal of Pharmaceutics}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0378-5173}, doi = {10.1016/j.ijpharm.2019.118461}, pages = {7}, year = {2019}, abstract = {The effect of non-spherical particle shapes on cellular uptake has been reported as a general design parameter to control cellular recognition of particulate drug carriers. Beside shape, also size and cell-particle ratio should mutually effect phagocytosis. Here, the capability to control cellular uptake of poly(epsilon-caprolactone) (PCL) based polymer micronetwork colloids (MNC), a carrier system that can be transferred to various shapes, is explored in vitro at test conditions allowing multiple cell-particle contacts. PCL-based MNC were synthesized as spheres with a diameter of similar to 6, similar to 10, and 13 mu m, loaded with a fluorescent dye by a specific technique of swelling, redispersion and drying, and transferred into different ellipsoidal shapes by a phantom stretching method. The boundaries of MNC deformability to prolate ellipsoid target shapes were systematically analyzed and found to be at an aspect ratio AR of similar to 4 as obtained by a phantom elongation epsilon(ph) of similar to 150\%. Uptake studies with a murine macrophages cell line showed shape dependency of phagocytosis for selected conditions when varying particle sizes (similar to 6 and 10 mu m),and shapes (epsilon(ph): 0, 75 or 150\%), cell-particle ratios (1:1, 1:2, 1:10, 1:50), and time points (1-24 h). For larger-sized MNC, there was no significant shape effect on phagocytosis as these particles may associate with more than one cell, thus increasing the possibility of phagocytosis by any of these cells. Accordingly, controlling shape effects on phagocytosis for carriers made from degradable polymers relevant for medical applications requires considering further parameters besides shape, such as kinetic aspects of the exposure and uptake by cells.}, language = {en} } @article{SchimkaKlierdeGuerenuetal.2019, author = {Schimka, Selina and Klier, Dennis Tobias and de Guerenu, Anna Lopez and Bastian, Philipp and Lomadze, Nino and Kumke, Michael Uwe and Santer, Svetlana}, title = {Photo-isomerization of azobenzene containing surfactants induced by near-infrared light using upconversion nanoparticles as mediator}, series = {Journal of physics : Condensed matter}, volume = {31}, journal = {Journal of physics : Condensed matter}, number = {12}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {0953-8984}, doi = {10.1088/1361-648X/aafcfa}, pages = {9}, year = {2019}, abstract = {Here we report on photo-isomerization of azobenzene containing surfactants induced during irradiation with near-infrared (NIR) light in the presence of upconversion nanoparticles (UCNPs) acting as mediator. The surfactant molecule consists of charged head group and hydrophobic tail with azobenzene group incorporated in alkyl chain. The azobenzene group can be reversible photo-isomerized between two states: trans- and cis- by irradiation with light of an appropriate wavelength. The trans-cis photo-isomerization is induced by UV light, while cis-trans isomerization proceeds either thermally in darkness, or can be accelerated by exposure to illumination with a longer wavelength typically in a blue/green range. We present the application of lanthanide doped UCNPs to successfully switch azobenzene containing surfactants from cis to trans conformation in bulk solution using NIR light. Using Tm-3(+) or Er-3(+) as activator ions, the UCNPs provide emissions in the spectral range of 450 nm < lambda(em) < 480 nm (for Tm-3(+), three and four photon induced emission) or 525 nm < lambda(em) < 545 nm (for Er-3(+), two photon induced emission), respectively. Especially for UCNPs containing Tm-3(+) a good overlap of the emissions with the absorption bands of the azobenzene is present. Under illumination of the surfactant solution with NIR light (lambda(ex) = 976 nm) in the presence of the Tm-3(+)-doped UCNPs, the relaxation time of cis-trans photo-isomerization was increased by almost 13 times compared to thermally induced isomerization. The influence of thermal heating due to the irradiation using NIR light was shown to be minor for solvents not absorbing in NIR spectral range (e.g. CHCl3) in contrast to water, which shows a distinct absorption in the NIR.}, language = {en} } @article{HaubitzJohnWessigetal.2019, author = {Haubitz, Toni and John, Leonard and Wessig, Pablo and Kumke, Michael Uwe}, title = {Photophysics of Acyl- and Ester-DBD Dyes}, series = {the journal of physical chemistry : A, Molecules, spectroscopy, kinetics, environment \& general theory}, volume = {123}, journal = {the journal of physical chemistry : A, Molecules, spectroscopy, kinetics, environment \& general theory}, number = {22}, publisher = {American Chemical Society}, address = {Washington}, issn = {1089-5639}, doi = {10.1021/acs.jpca.9b02973}, pages = {4717 -- 4726}, year = {2019}, abstract = {A new generation of wavelength-tunable, fluorescent dyes, so-called DBD ([1,3]dioxolo[4,5-f][1,3]benzodioxole) dyes, were developed a few years ago, and they showed great potential as probes, for example, for fluorescence microscopy. However, their photophysics is not fully explored and leaves open questions regarding their large fluorescence Stokes shifts and sensitivity to solvent conditions of differently substituted DBD dyes. To improve the understanding of the influence of the substitution pattern of the DBD dyes on their respective photophysics, transient absorption spectroscopy (TAS) was used, that is, a pump-probe experiment on the femtosecond timescale. TAS allows measurements of excited states, ground state recovery, solvent relaxation, and fluorescence properties on time scales of up to several nanoseconds. Two different DBD dye samples were investigated: aryl- and ester-substituted DBD dyes. Experiments were carried out in solvents with different polarities using different excitation energies and at different viscosities. Based on the experimental data and theoretical calculations, we were able to determine the conformational changes of the molecule due to electronic excitation and were able to investigate solvent relaxation processes for both types of DBD dyes. By generalizing the theory for quadrupole-induced solvent relaxation developed by Togashi et al., we derived quadrupole moments of both molecules in the ground and excited state. Our data showed differences in the binding of polar solvent molecules to the dyes depending on the substituent on the DBD dye. In the case of water as the solvent, an additional efficient quenching process in the electronically excited state was revealed, which was indicated by the observation of solvated electrons in the TAS signals.}, language = {en} } @article{LuedeckeWeidnerSchlaad2019, author = {L{\"u}decke, Nils and Weidner, Steffen M. and Schlaad, Helmut}, title = {Poly(2-oxazoline)s Based on Phenolic Acids}, series = {Macromolecular rapid communications}, volume = {41}, journal = {Macromolecular rapid communications}, number = {1}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1022-1336}, doi = {10.1002/marc.201900404}, pages = {5}, year = {2019}, abstract = {A series of phenolic-acid-based 2-oxazoline monomers with methoxy-substituted phenyl and cinnamyl side chains is synthesized and polymerized in a microwave reactor at 140 °C using methyl tosylate as the initiator. The obtained poly(2-oxazoline)s are characterized by NMR spectroscopy, MALDI-TOF mass spectrometry, and size-exclusion chromatography (SEC). Kinetic studies reveal that the microwave-assisted polymerization is fast and completed within less than ≈10 min for low monomer-to-initiator ratios of ≤25. Polymers with number-average molar masses of up to 6500 g mol-1 and low dispersity (1.2-1.3) are produced. The aryl methyl ethers are successfully cleaved with aluminum triiodide/N,N′-diisopropylcarbodiimide to give a poly(2-oxazoline) with pendent catechol groups.}, language = {en} } @article{AlNakeebKochovskiLietal.2019, author = {Al Nakeeb, Noah and Kochovski, Zdravko and Li, Tingting and Zhang, Youjia and Lu, Yan and Schmidt, Bernhard V. K. J.}, title = {Poly(ethylene glycol) brush-b-poly(N-vinylpyrrolidone)-based double hydrophilic block copolymer particles crosslinked via crystalline alpha-cyclodextrin domains}, series = {RSC Advances}, volume = {9}, journal = {RSC Advances}, number = {9}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {2046-2069}, doi = {10.1039/c8ra10672j}, pages = {4993 -- 5001}, year = {2019}, abstract = {Self-assembly of block copolymers is a significant area of polymer science. The self-assembly of completely water-soluble block copolymers is of particular interest, albeit a challenging task. In the present work the self-assembly of a linear-brush architecture block copolymer, namely poly(N-vinylpyrrolidone)-b-poly(oligoethylene glycol methacrylate) (PVP-b-POEGMA), in water is studied. Moreover, the assembled structures are crosslinked via alpha-CD host/guest complexation in a supramolecular way. The crosslinking shifts the equilibrium toward aggregate formation without switching off the dynamic equilibrium of double hydrophilic block copolymer (DHBC). As a consequence, the self-assembly efficiency is improved without extinguishing the unique DHBC self-assembly behavior. In addition, decrosslinking could be induced without a change in concentration by adding a competing complexation agent for alpha-CD. The self-assembly behavior was followed by DLS measurement, while the presence of the particles could be observed via cryo-TEM before and after crosslinking.}, language = {en} } @article{BehrendtHessLehmannetal.2019, author = {Behrendt, Felix Nicolas and Hess, Andreas and Lehmann, Max and Schmidt, Bernd and Schlaad, Helmut}, title = {Polymerization of cystine-derived monomers}, series = {Polymer Chemistry}, volume = {10}, journal = {Polymer Chemistry}, number = {13}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1759-9954}, doi = {10.1039/c9py00118b}, pages = {1636 -- 1641}, year = {2019}, abstract = {Cystine was used as a platform chemical to prepare cyclic and acyclic monomers for entropy-driven ringopening polymerization (ED-ROMP) via olefin or disulfide metathesis and for step-growth polymerization. The olefin ED-ROMP of an olefin/disulfide containing 16-atom macrocycle using the 3rd generation Grubbs catalyst was examined in greater detail. Kinetic studies revealed that the catalyst turned inactive during the polymerization, which limited the achievable (apparent) polymer molar mass to similar to 70 kg mol(-1). Such limitation could be overcome with the disulfide ED-ROMP of the same macrocycle to yield polymers with molar masses of up to 180 kg mol(-1). The step-growth polymerizations of acyclic diene and dithiol monomers via olefin metathesis or oxidation were far less effective and yielded just low molar mass polymers or oligomers; photopolymerization of a thiol-ene monomer produced a polyester with a molar mass of 35 kg mol(-1).}, language = {en} } @article{JiangMansfeldKratzetal.2019, author = {Jiang, Yi and Mansfeld, Ulrich and Kratz, Karl and Lendlein, Andreas}, title = {Programmable microscale stiffness pattern of flat polymeric substrates by temperature-memo technology}, series = {MRS Communications}, volume = {9}, journal = {MRS Communications}, number = {1}, publisher = {Cambridge Univ. Press}, address = {New York}, issn = {2159-6859}, doi = {10.1557/mrc.2019.24}, pages = {181 -- 188}, year = {2019}, abstract = {Temperature-memory technology was utilized to generate flat substrates with a programmable stiffness pattern from cross-linked poly(ethylene-co-vinyl acetate) substrates with cylindrical microstructures. Programmed substrates were obtained by vertical compression at temperatures in the range from 60 to 100 degrees C and subsequent cooling, whereby a flat substrate was achieved by compression at 72 degrees C, as documented by scanning electron microscopy and atomic force microscopy (AFM). AFM nanoindentation experiments revealed that all programmed substrates exhibited the targeted stiffness pattern. The presented technology for generating polymeric substrates with programmable stiffness pattern should be attractive for applications such as touchpads. optical storage, or cell instructive substrates.}, language = {en} } @article{YuQuanMeietal.2019, author = {Yu, Hongtao and Quan, Ting and Mei, Shilin and Kochovski, Zdravko and Huang, Wei and Meng, Hong and Lu, Yan}, title = {Prompt Electrodeposition of Ni Nanodots on Ni Foam to Construct a High-Performance Water-Splitting Electrode}, series = {Nano-Micro Letters}, volume = {11}, journal = {Nano-Micro Letters}, number = {41}, publisher = {Shanghai JIAO TONG univ press}, address = {Shanghai}, issn = {2311-6706}, doi = {10.1007/s40820-019-0269-x}, pages = {13}, year = {2019}, abstract = {HighlightsFacile electrodeposition for fabricating active Ni nanodots (NiNDs) on Ni foam (NF) is shown.Binder- and heteroatom-free recyclable NiO/NiNDs@NF electrodes are efficiently made.NiO/NiNDs@NF bifunctional catalytic electrodes are used for water splitting. AbstractIn past decades, Ni-based catalytic materials and electrodes have been intensively explored as low-cost hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) catalysts for water splitting. With increasing demands for Ni worldwide, simplifying the fabrication process, increasing Ni recycling, and reducing waste are tangible sustainability goals. Here, binder-free, heteroatom-free, and recyclable Ni-based bifunctional catalytic electrodes were fabricated via a one-step quick electrodeposition method. Typically, active Ni nanodot (NiND) clusters are electrodeposited on Ni foam (NF) in Ni(NO3)(2) acetonitrile solution. After drying in air, NiO/NiND composites are obtained, leading to a binder-free and heteroatom-free NiO/NiNDs@NF catalytic electrode. The electrode shows high efficiency and long-term stability for catalyzing hydrogen and oxygen evolution reactions at low overpotentials ((10)(HER)=119mV and (50)(OER)=360mV) and can promote water catalysis at 1.70V@10mAcm(-2). More importantly, the recovery of raw materials (NF and Ni(NO3)(2)) is quite easy because of the solubility of NiO/NiNDs composites in acid solution for recycling the electrodes. Additionally, a large-sized (S similar to 70cm(2)) NiO/NiNDs@NF catalytic electrode with high durability has also been constructed. This method provides a simple and fast technology to construct high-performance, low-cost, and environmentally friendly Ni-based bifunctional electrocatalytic electrodes for water splitting.}, language = {en} } @article{BalkBehlLendlein2019, author = {Balk, Maria and Behl, Marc and Lendlein, Andreas}, title = {Quadruple-shape hydrogels}, series = {Smart materials and structures}, volume = {28}, journal = {Smart materials and structures}, number = {5}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {0964-1726}, doi = {10.1088/1361-665X/ab0e91}, pages = {10}, year = {2019}, abstract = {The capability of directed movements by two subsequent shape changes could be implemented in shape-memory hydrogels by incorporation of two types of crystallizable side chains While in non-swollen polymer networks even more directed movements could be realized, the creation of multi-shape hydrogels is still a challenge. We hypothesize that a quadruple-shape effect in hydrogels can be realized, when a swelling capacity almost independent of temperature is generated, whereby directed movements could be enabled, which are not related to swelling. In this case, entropy elastic recovery could be realized by hydrophilic segments and the fixation of different macroscopic shapes by means of three semi-crystalline side chains generating temporary crosslinks. Monomethacrylated semi-crystalline oligomers were connected as side chains in a hydrophilic polymer network via radical copolymerization. Computer assisted modelling was utilized to design a demonstrator capable of complex shape shifts by creating a casting mold via 3D printing from polyvinyl alcohol. The demonstrator was obtained after copolymerization of polymer network forming components within the mold, which was subsequently dissolved in water. A thermally-induced quadruple-shape effect was realized after equilibrium swelling of the polymer network in water. Three directed movements were successfully obtained when the temperature was continuously increased from 5 degrees C to 90 degrees C with a recovery ratio of the original shape above 90\%. Hence, a thermally-induced quadruple-shape effect as new record for hydrogels was realized. Here, the temperature range for the multi-shape effect was limited by water as swelling media (0 degrees C-100 degrees C), simultaneously distinctly separated thermal transitions were required, and the overall elasticity indispensable for successive deformations was reduced as result of partially chain segment orientation induced by swelling in water. Conclusively the challenges for penta- or hexa-shape gels are the design of systems enabling higher elastic deformability and covering a larger temperature range by switching to a different solvent.}, language = {en} } @article{WanjikuYamamotoKlosseketal.2019, author = {Wanjiku, Barbara and Yamamoto, Kenji and Klossek, Andre and Schumacher, Fabian and Pischon, Hannah and Mundhenk, Lars and Rancan, Fiorenza and Judd, Martyna M. and Ahmed, Muniruddin and Zoschke, Christian and Kleuser, Burkhard and R{\"u}hl, Eckart and Sch{\"a}fer-Korting, Monika}, title = {Qualifying X-ray and Stimulated Raman Spectromicroscopy for Mapping Cutaneous Drug Penetration}, series = {Analytical chemistry}, volume = {91}, journal = {Analytical chemistry}, number = {11}, publisher = {American Chemical Society}, address = {Washington}, issn = {0003-2700}, doi = {10.1021/acs.analchem.9b00519}, pages = {7208 -- 7214}, year = {2019}, abstract = {Research on topical drug delivery relies on reconstructed human skin (RHS) in addition to ex vivo human and animal skin, each with specific physiological features. Here, we compared the penetration of dexamethasone from an ethanolic hydroxyethyl cellulose gel into ex vivo human skin, murine skin, and RHS. For comprehensive insights into skin morphology and penetration enhancing mechanisms, scanning transmission X-ray microscopy (STXM), liquid chromatography tandem mass spectrometry (LC-MS/MS), and stimulated Raman spectromicroscopy (SRS) were combined. STXM offers high spatial resolution with label-free drug detection and is therefore sensitive to tissue damage. Despite differences in sample preparation and data analysis, the amounts of dexamethasone in RHS, detected and quantified by STXM and LC-MS/MS, were very similar and increased during the first 100 min of exposure. SRS revealed interactions between the gel and the stratum corneum or, more specifically, its protein and lipid structures. Similar to both types of ex vivo skin, higher protein-to-lipid ratios within the stratum corneum of RHS indicated reduced lipid amounts after 30 min of ethanol exposure. Extended ethanol exposure led to a continued reduction of lipids in the ex vivo matrixes, while protein integrity appeared to be compromised in RHS, which led to declining protein signals. In conclusion, LC-MS/MS proved the predictive capability of STXM for label-free drug detection. Combining STXM with SRS precisely dissected the penetration enhancing effects of ethanol. Further studies on topical drug delivery should consider the potential of these complementary techniques.}, language = {en} } @article{MinkMcHardyBresseletal.2019, author = {Mink, Albert and McHardy, Christopher and Bressel, Lena and Rauh, Cornelia and Krause, Mathias J.}, title = {Radiative transfer lattice Boltzmann methods}, series = {Journal of quantitative spectroscopy \& radiative transfer}, volume = {243}, journal = {Journal of quantitative spectroscopy \& radiative transfer}, publisher = {Pergamon Press}, address = {Oxford}, issn = {0022-4073}, doi = {10.1016/j.jqsrt.2019.106810}, year = {2019}, abstract = {The numerical prediction of radiative transport is a challenging task due to the complexity of the radiative transport equation. We apply the lattice Boltzmann method (LBM), originally developed for fluid flow problems, to solve the radiative transport in volume. One model (meso RTLBM) is derived directly from a discretization of the radiative transport equation, yielding in a precise but numerical costly scheme. The second model (macro RTLBM) solves the Helmholtz equation, which is a proper approximation for highly scattering volumes. Both numerical algorithms are validated against Monte-Carlo data for a set of 35 optical parameters, which correspond to radiative transport ranging from ballistic to diffuse regimes. Together with a set of four benchmark simulations, the comprehensive validation concludes the overall quality and detects asymptotic trends for radiative transport LBM. Furthermore, an accuracy map is presented, which summarizes the error for all parameters. This graph allows to determine the validity range for both radiative transport LBM at a glance. Finally, comprehensive guidelines are formulated to facilitate the choice of the radiative transport LBM model.}, language = {en} } @article{LendleinGould2019, author = {Lendlein, Andreas and Gould, Oliver E. C.}, title = {Reprogrammable recovery and actuation behaviour of shape-memory polymers}, series = {Nature reviews. Materials}, volume = {4}, journal = {Nature reviews. Materials}, number = {2}, publisher = {Nature Publ. Group}, address = {London}, issn = {2058-8437}, doi = {10.1038/s41578-018-0078-8}, pages = {116 -- 133}, year = {2019}, abstract = {Shape memory is the capability of a material to be deformed and fixed into a temporary shape. Recovery of the original shape can then be triggered only by an external stimulus. Shape-memory polymers are highly deformable materials that can be programmed to recover a memorized shape in response to a variety of environmental and spatially localized stimuli as a one-way effect. The shape-memory function can also be generated as a reversible effect enabling actuation behaviour through macroscale deformation and processing, specifically by dictating the macromolecular orientation of actuation units and of the skeleton structure of geometry-determining units in the polymers. Shape-memory polymers can be programmed and reprogrammed into arbitrary shapes. Both recovery and actuation behaviour are reprogrammable. In this Review, we outline the common basis and key differences between the two shape-memory behaviours of polymers in terms of mechanism, fabrication schemes and characterization methods. We discuss which combination of macromolecular architecture and macroscale processing is necessary for coordinated, decentralized and responsive physical behaviour. The extraction of relevant thermomechanical information is described, and design criteria are shown for microscale and macroscale morphologies to gain high levels of recovered or actuation strains as well as on-demand 2D-to-3D shape transformations. Finally, real-world applications and key future challenges are highlighted.}, language = {en} } @article{SaretiaMachatschekSchulzetal.2019, author = {Saretia, Shivam and Machatschek, Rainhard Gabriel and Schulz, Burkhard and Lendlein, Andreas}, title = {Reversible 2D networks of oligo(epsilon-caprolactone) at the air-water interface}, series = {Biomedical Materials}, volume = {14}, journal = {Biomedical Materials}, number = {3}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {1748-6041}, doi = {10.1088/1748-605X/ab0cef}, pages = {10}, year = {2019}, abstract = {Hydroxyl terminated oligo(epsilon-caprolactone) (OCL) monolayers were reversibly cross-linked forming two dimensional networks (2D) at the air-water interface. The equilibrium reaction with glyoxal as the cross-linker is pH-sensitive. Pronounced contraction in the area of the prepared 2DOCL films in dependence of surface pressure and time revealed the process of the reaction. Cross-linking inhibited crystallization and retarded enzymatic degradation of the OCLfilm. Altering the subphase pH led to a cleavage of the covalent acetal cross-links. The reversibility of the covalent acetal cross-links was proved by observing an identical isotherm as non-cross-linked sample. Besides as model systems, these customizable reversible OCL2D networks are intended for use as pHresponsive drug delivery systems or functionalized cell culture substrates.}, language = {en} } @article{DebsharmaBehrendtLaschewskyetal.2019, author = {Debsharma, Tapas and Behrendt, Felix Nicolas and Laschewsky, Andre and Schlaad, Helmut}, title = {Ring-opening metathesis polymerization of biomass-derived levoglucosenol}, series = {Angewandte Chemie : a journal of the Gesellschaft Deutscher Chemiker}, volume = {58}, journal = {Angewandte Chemie : a journal of the Gesellschaft Deutscher Chemiker}, number = {20}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1433-7851}, doi = {10.1002/anie.201814501}, pages = {6718 -- 6721}, year = {2019}, abstract = {The readily available cellulose-derived bicyclic compound levoglucosenol was polymerized through ring-opening metathesis polymerization (ROMP) to yield polylevoglucosenol as a novel type of biomass-derived thermoplastic polyacetal, which, unlike polysaccharides, contains cyclic as well as linear segments in its main chain. High-molar-mass polyacetals with apparent weight-average molar masses of up to 100kgmol(-1) and dispersities of approximately 2 were produced despite the non-living/controlled character of the polymerization due to irreversible deactivation or termination of the catalyst/active chain ends. The resulting highly functionalized polyacetals are glassy in bulk with a glass transition temperature of around 100 degrees C. In analogy to polysaccharides, polylevoglucosenol degrades slowly in an acidic environment.}, language = {en} } @article{BreternitzLehmannBarnettetal.2019, author = {Breternitz, Joachim and Lehmann, Frederike and Barnett, Sarah A. and Nowell, Harriott and Schorr, Susan}, title = {Role of the Iodide-methylammonium interaction in the ferroelectricity of CH3NH3PbI3}, series = {Angewandte Chemie - international edition}, volume = {59}, journal = {Angewandte Chemie - international edition}, number = {1}, publisher = {John Wiley \& Sons, Inc.}, address = {New Jersey}, pages = {5}, year = {2019}, abstract = {Excellent conversion efficiencies of over 20\% and facile cell production have placed hybrid perovskites at the forefront of novel solar cell materials, with CH3NH3PbI3 being an archetypal compound. The question why CH3NH3PbI3 has such extraordinary characteristics, particularly a very efficient power conversion from absorbed light to electrical power, is hotly debated, with ferroelectricity being a promising candidate. This does, however, require the crystal structure to be non-centrosymmetric and we herein present crystallographic evidence as to how the symmetry breaking occurs on a crystallographic and, therefore, long-range level. Although the molecular cation CH3NH3+ is intrinsically polar, it is heavily disordered and this cannot be the sole reason for the ferroelectricity. We show that it, nonetheless, plays an important role, as it distorts the neighboring iodide positions from their centrosymmetric positions.}, language = {en} } @article{BaldSchuermannEbeletal.2019, author = {Bald, Ilko and Sch{\"u}rmann, Robin Mathis and Ebel, Kenny and Nicolas, Christophe and Milosavljevic, Aleksandar R.}, title = {Role of valence band states and plasmonic enhancement in electron-transfer-induced transformation of nitrothiophenol}, series = {The Journal of Physical Chemistry Letters}, volume = {10}, journal = {The Journal of Physical Chemistry Letters}, publisher = {American Chemical Society}, address = {Washington}, issn = {1948-7185}, doi = {10.1021/acs.jpclett.9b00848}, pages = {3153 -- 3158}, year = {2019}, abstract = {Hot-electron-induced reactions are more and more recognized as a critical and ubiquitous reaction in heterogeneous catalysis. However, the kinetics of these reactions is still poorly understood, which is also due to the complexity of plasmonic nanostructures. We determined the reaction rates of the hot-electron-mediated reaction of 4-nitrothiophenol (NTP) on gold nanoparticles (AuNPs) using fractal kinetics as a function of the laser wavelength and compared them with the plasmonic enhancement of the system. The reaction rates can be only partially explained by the plasmonic response of the NPs. Hence, synchrotron X-ray photoelectron spectroscopy (XPS) measurements of isolated NTP-capped AuNP clusters have been performed for the first time. In this way, it was possible to determine the work function and the accessible valence band states of the NP systems. The results show that besides the plasmonic enhancement, the reaction rates are strongly influenced by the local density of the available electronic states of the system.}, language = {en} } @article{KocSimovichSchoenemannetal.2019, author = {Koc, Julian and Simovich, Tomer and Sch{\"o}nemann, Eric and Chilkoti, Ashutosh and Gardner, Harrison and Swain, Geoffrey W. and Hunsucker, Kelli and Laschewsky, Andr{\´e} and Rosenhahn, Axel}, title = {Sediment challenge to promising ultra-low fouling hydrophilic surfaces in the marine environment}, series = {Biofouling : the journal of bioadhesion and biofilm research}, volume = {35}, journal = {Biofouling : the journal of bioadhesion and biofilm research}, number = {4}, publisher = {Taylor \& Francis}, address = {London}, issn = {0892-7014}, doi = {10.1080/08927014.2019.1611790}, pages = {454 -- 462}, year = {2019}, abstract = {Hydrophilic coatings exhibit ultra-low fouling properties in numerous laboratory experiments. In stark contrast, the antifouling effect of such coatings in vitro failed when performing field tests in the marine environment. The fouling release performance of nonionic and zwitterionic hydrophilic polymers was substantially reduced compared to the controlled laboratory environment. Microscopy and spectroscopy revealed that a large proportion of the accumulated material in field tests contains inorganic compounds and diatomaceous soil. Diatoms adhered to the accumulated material on the coating, but not to the pristine polymer. Simulating field tests in the laboratory using sediment samples collected from the test sites showed that incorporated sand and diatomaceous earth impairs the fouling release characteristics of the coatings. When exposed to marine sediment from multiple locations, particulate matter accumulated on these coatings and served as attachment points for diatom adhesion and enhanced fouling. Future developments of hydrophilic coatings should consider accumulated sediment and its potential impact on the antifouling performance.}, language = {en} } @article{KroepflFrancesconiSchwerdtleetal.2019, author = {Kroepfl, Nina and Francesconi, Kevin A. and Schwerdtle, Tanja and Kuehnelt, Doris}, title = {Selenoneine and ergothioneine in human blood cells determined simultaneously by HPLC/ICP-QQQ-MS}, series = {Journal of Analytical Atomic Spectrometry}, volume = {34}, journal = {Journal of Analytical Atomic Spectrometry}, number = {1}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {0267-9477}, doi = {10.1039/c8ja00276b}, pages = {127 -- 134}, year = {2019}, abstract = {The possible relevance to human health of selenoneine and its sulfur-analogue ergothioneine has generated interest in their quantitative determination in biological samples. To gain more insight into the similarities and differences of these two species, a method for their simultaneous quantitative determination in human blood cells using reversed-phase high performance liquid chromatography (RP-HPLC) coupled to inductively coupled plasma triple quadrupole mass spectrometry (ICP-QQQ-MS) is presented. Spectral interferences hampering the determination of sulfur and selenium by ICPMS are overcome by introducing oxygen to the reaction cell. To access selenoneine and ergothioneine in the complex blood matrix, lysis of the cells with cold water followed by cut-off filtration (3000 Da) is performed. Recoveries based on blood cells spiked with selenoneine and ergothioneine were between 80\% and 85\%. The standard deviation of the method was around 0.10 mg S per L for ergothioneine (corresponding to relative standard deviations (RSD) between 10-1\% for ergothioneine concentrations of 1-10 mg S per L) and 0.25 g Se per L for selenoneine (RSDs of 25-2\% for concentrations of 1-10 g Se per L). The method was applied to blood cell samples from three volunteers which showed selenoneine and ergothioneine concentrations in the range of 3.25 to 7.35 g Se per L and 0.86 to 6.44 mg S per L, respectively. The method is expected to be of wide use in future studies investigating the dietary uptake of selenoneine and ergothioneine and their relevance in human health.}, language = {en} } @article{RuszkiewiczdeMacedoMirandaVizueteetal.2019, author = {Ruszkiewicz, Joanna A. and de Macedo, Gabriel Teixeira and Miranda-Vizuete, Antonio and Bowman, Aaron B. and Bornhorst, Julia and Schwerdtle, Tanja and Antunes Soares, Felix A. and Aschner, Michael}, title = {Sex-Specific response of caenorhabditis elegans to Methylmercury Toxicity}, series = {Neurotoxicity Research}, volume = {35}, journal = {Neurotoxicity Research}, number = {1}, publisher = {Springer}, address = {New York}, issn = {1029-8428}, doi = {10.1007/s12640-018-9949-4}, pages = {208 -- 216}, year = {2019}, abstract = {Methylmercury (MeHg), an abundant environmental pollutant, has long been known to adversely affect neurodevelopment in both animals and humans. Several reports from epidemiological studies, as well as experimental data indicate sex-specific susceptibility to this neurotoxicant; however, the molecular bases of this process are still not clear. In the present study, we used Caenorhabditis elegans (C. elegans), to investigate sex differences in response to MeHg toxicity during development. Worms at different developmental stage (L1, L4, and adult) were treated with MeHg for 1h. Lethality assays revealed that male worms exhibited significantly higher resistance to MeHg than hermaphrodites, when at L4 stage or adults. However, the number of worms with degenerated neurons was unaffected by MeHg, both in males and hermaphrodites. Lower susceptibility of males was not related to changes in mercury (Hg) accumulation, which was analogous for both wild-type (wt) and male-rich him-8 strain. Total glutathione (GSH) levels decreased upon MeHg in him-8, but not in wt. Moreover, the sex-dependent response of the cytoplasmic thioredoxin system was observedmales exhibited significantly higher expression of thioredoxin TRX-1, and thioredoxin reductase TRXR-1 expression was downregulated upon MeHg treatment only in hermaphrodites. These outcomes indicate that the redox status is an important contributor to sex-specific sensitivity to MeHg in C. elegans.}, language = {en} } @article{YuanNeriZakrietal.2019, author = {Yuan, Jinkai and Neri, Wilfrid and Zakri, Cecile and Merzeau, Pascal and Kratz, Karl and Lendlein, Andreas and Poulin, Philippe}, title = {Shape memory nanocomposite fibers for untethered high-energy microengines}, series = {Science}, volume = {365}, journal = {Science}, number = {6449}, publisher = {American Assoc. for the Advancement of Science}, address = {Washington}, issn = {0036-8075}, doi = {10.1126/science.aaw3722}, pages = {155 -- 158}, year = {2019}, abstract = {Classic rotating engines are powerful and broadly used but are of complex design and difficult to miniaturize. It has long remained challenging to make large-stroke, high-speed, high-energy microengines that are simple and robust. We show that torsionally stiffened shape memory nanocomposite fibers can be transformed upon insertion of twist to store and provide fast and high-energy rotations. The twisted shape memory nanocomposite fibers combine high torque with large angles of rotation, delivering a gravimetric work capacity that is 60 times higher than that of natural skeletal muscles. The temperature that triggers fiber rotation can be tuned. This temperature memory effect provides an additional advantage over conventional engines by allowing for the tunability of the operation temperature and a stepwise release of stored energy.}, language = {en} } @article{MazurekBudzynskaRazzaqBehletal.2019, author = {Mazurek-Budzynska, Magdalena and Razzaq, Muhammad Yasar and Behl, Marc and Lendlein, Andreas}, title = {Shape-Memory Polymers}, series = {Functional Polymers}, journal = {Functional Polymers}, publisher = {Springer}, address = {Cham}, isbn = {978-3-319-95987-0}, issn = {2510-3458}, doi = {10.1007/978-3-319-95987-0_18}, pages = {605 -- 663}, year = {2019}, abstract = {Shape-memory polymers (SMPs) are stimuli-sensitive materials capable of changing their shape on demand. A shape-memory function is a result of the polymer architecture together with the application of a specific programming procedure. Various possible mechanisms to induce the shape-memory effect (SME) can be realized, which can be based on thermal transitions of switching domains or on reversible molecular switches (e.g., supramolecular interactions, reversible covalent bonds). Netpoints, which connect the switching domains and determine the permanent shape, can be either provided by covalent bonds or by physical intermolecular interactions, such as hydrogen bonds or crystallites. This chapter reviews different ways of implementing the phenomenon of programmable changes in the polymer shape, including the one-way shape-memory effect (1-W SME), triple-and multi-shape effects (TSE/ MSE), the temperature-memory effect (TME), and reversible shape-memory effects, which can be realized in constant stress conditions (rSME), or in stress-free conditions (reversible bidirectional shape-memory effect (rbSME)). Furthermore, magnetically actuated SMPs and shape-memory hydrogels (SMHs) are described to show the potential of the SMP technology in biomedical applications and multifunctional approaches.}, language = {en} } @article{ReinthalerJohanssonBrauneetal.2019, author = {Reinthaler, Markus and Johansson, Johan Backemo and Braune, Steffen and Al-Hindwan, Haitham Saleh Ali and Lendlein, Andreas and Jung, Friedrich}, title = {Shear-induced platelet adherence and activation in an in-vitro dynamic multiwell-plate system}, series = {Clinical hemorheology and microcirculation : blood flow and vessels}, volume = {71}, journal = {Clinical hemorheology and microcirculation : blood flow and vessels}, number = {2}, publisher = {IOS Press}, address = {Amsterdam}, issn = {1386-0291}, doi = {10.3233/CH-189410}, pages = {183 -- 191}, year = {2019}, abstract = {Circulating blood cells are prone to varying flow conditions when contacting cardiovascular devices. For a profound understanding of the complex interplay between the blood components/cells and cardiovascular implant surfaces, testing under varying shear conditions is required. Here, we study the influence of arterial and venous shear conditions on the in vitro evaluation of the thrombogenicity of polymer-based implant materials. Medical grade poly(dimethyl siloxane) (PDMS), polyethylene terephthalate (PET) and polytetrafluoroethylene (PTFE) films were included as reference materials. The polymers were exposed to whole blood from healthy humans. Blood was agitated orbitally at low (venous shear stress: 2.8 dyne. cm(-2)) and high (arterial shear stress: 22.2 dyne .cm(-2)) agitation speeds in a well-plate based test system. Numbers of non-adherent platelets, platelet activation (P-Selectin positive platelets), platelet function (PFA100 closure times) and platelet adhesion (laser scanning microscopy (LSM)) were determined. Microscopic data and counting of the circulating cells revealed increasing numbers of material-surface adherent platelets with increasing agitation speed. Also, activation of the platelets was substantially increased when tested under the high shear conditions (P-Selectin levels, PFA-100 closure times). At low agitation speed, the platelet densities did not differ between the three materials. Tested at the high agitation speed, lowest platelet densities were observed on PDMS, intermediate levels on PET and highest on PTFE. While activation of the circulating platelets was affected by the implant surfaces in a similar manner, PFA closure times did not reflect this trend. Differences in the thrombogenicity of the studied polymers were more pronounced when tested at high agitation speed due to the induced shear stresses. Testing under varying shear stresses, thus, led to a different evaluation of the implant thrombogenicity, which emphasizes the need for testing under various flow conditions. Our data further confirmed earlier findings where the same reference implants were tested under static (and not dynamic) conditions and with fresh human platelet rich plasma instead of whole blood. This supports that the application of common reference materials may improve inter-study comparisons, even under varying test conditions.}, language = {en} } @article{GrosskopfTierschKoetzetal.2019, author = {Großkopf, S{\"o}ren and Tiersch, Brigitte and Koetz, Joachim and Mix, Andreas and Hellweg, Thomas}, title = {Shear-Induced Transformation of Polymer-Rich Lamellar Phases to Micron-Sized Vesicles}, series = {Langmuir}, volume = {35}, journal = {Langmuir}, number = {8}, publisher = {American Chemical Society}, address = {Washington}, issn = {0743-7463}, doi = {10.1021/acs.langmuir.8602786}, pages = {3048 -- 3057}, year = {2019}, abstract = {In the present work, we study the shear-induced transformation of polymer-rich lamellar phases into vesicles. The evolution of vesicle size is studied by different scattering techniques, rheology, and microscopy methods. The lamellar phase found in the system D2O/o-xylene/Pluronic PE9400/C(8)TAB can be fully transformed to multilamellar vesicles (MLVs) by applying shear. The size of the MLVs is proportional to the inverse square root of the shear rate. Hence, the polymer based quaternary system behaves similar to lamellar phases based on small surfactant molecules. Additionally, we found a growth effect leading to a size increase of the vesicles after shearing was stopped.}, language = {en} } @article{RotheZhaoKewesetal.2019, author = {Rothe, Martin and Zhao, Yuhang and Kewes, G{\"u}nter and Kochovski, Zdravko and Sigle, Wilfried and van Aken, Peter A. and Koch, Christoph and Ballauff, Matthias and Lu, Yan and Benson, Oliver}, title = {Silver nanowires with optimized silica coating as versatile plasmonic resonators}, series = {Scientific reports}, volume = {9}, journal = {Scientific reports}, publisher = {Nature Publ. Group}, address = {London}, issn = {2045-2322}, doi = {10.1038/s41598-019-40380-5}, pages = {12}, year = {2019}, abstract = {Metal nanoparticles are the most frequently used nanostructures in plasmonics. However, besides nanoparticles, metal nanowires feature several advantages for applications. Their elongation offers a larger interaction volume, their resonances can reach higher quality factors, and their mode structure provides better coupling into integrated hybrid dielectric-plasmonic circuits. It is crucial though, to control the distance of the wire to a supporting substrate, to another metal layer or to active materials with sub-nanometer precision. A dielectric coating can be utilized for distance control, but it must not degrade the plasmonic properties. In this paper, we introduce a controlled synthesis and coating approach for silver nanowires to fulfill these demands. We synthesize and characterize silver nanowires of around 70 nm in diameter. These nanowires are coated with nm-sized silica shells using a modified Stober method to achieve a homogeneous and smooth surface quality. We use transmission electron microscopy, dark-field microscopy and electron-energy loss spectroscopy to study morphology and plasmonic resonances of individual nanowires and quantify the influence of the silica coating. Thorough numerical simulations support the experimental findings showing that the coating does not deteriorate the plasmonic properties and thus introduce silver nanowires as usable building blocks for integrated hybrid plasmonic systems.}, language = {en} }