TY - JOUR A1 - Yuan, Jinkai A1 - Neri, Wilfrid A1 - Zakri, Cecile A1 - Merzeau, Pascal A1 - Kratz, Karl A1 - Lendlein, Andreas A1 - Poulin, Philippe T1 - Shape memory nanocomposite fibers for untethered high-energy microengines JF - Science N2 - 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. Y1 - 2019 U6 - https://doi.org/10.1126/science.aaw3722 SN - 0036-8075 SN - 1095-9203 VL - 365 IS - 6449 SP - 155 EP - 158 PB - American Assoc. for the Advancement of Science CY - Washington ER - TY - JOUR A1 - Ugwuja, Chidinma G. A1 - Adelowo, Olawale O. A1 - Ogunlaja, Aemere A1 - Omorogie, Martins O. A1 - Olukanni, Olumide D. A1 - Ikhimiukor, Odion O. A1 - Iermak, Ievgeniia A1 - Kolawole, Gabriel A. A1 - Günter, Christina A1 - Taubert, Andreas A1 - Bodede, Olusola A1 - Moodley, Roshila A1 - Inada, Natalia M. A1 - Camargo, Andrea S.S. de A1 - Unuabonah, Emmanuel Iyayi T1 - Visible-Light-Mediated Photodynamic Water Disinfection @ Bimetallic-Doped Hybrid Clay Nanocomposites JF - ACS applied materials & interfaces N2 - This study reports a new class of photocatalytic hybrid clay nanocomposites prepared from low-cost sources (kaolinite clay and Carica papaya seeds) doped with Zn and Cu salts via a solvothermal process. X-ray diffraction analysis suggests that Cu-doping and Cu/Zn-doping introduce new phases into the crystalline structure of Kaolinite clay, which is linked to the reduced band gap of kaolinite from typically between 4.9 and 8.2 eV to 2.69 eV for Cu-doped and 1.5 eV for Cu/Zn hybrid clay nanocomposites (Nisar, J.; Arhammar, C.; Jamstorp, E.; Ahuja, R. Phys. Rev. B 2011, 84, 075120). In the presence of solar light irradiation, Cu- and Cu/Zn-doped nanocomposites facilitate the electron hole pair separation. This promotes the generation of singlet oxygen which in turn improves the water disinfection efficiencies of these novel nanocomposite materials. The nanocomposite materials were further characterized using high-resolution scanning electron microscopy, fluorimetry, therrnogravimetric analysis, and Raman spectroscopy. The breakthrough times of the nanocomposites for a fixed bed mode of disinfection of water contaminated with 2.32 x 10(7) cfu/mL E. coli ATCC 25922 under solar light irradiation are 25 h for Zn-doped, 30 h for Cu-doped, and 35 h for Cu/Zn-doped nanocomposites. In the presence of multidrug and multimetal resistant strains of E. coli, the breakthrough time decreases significantly. Zn-only doped nanocomposites are not photocatalytically active. In the absence of light, the nanocomposites are still effective in decontaminating water, although less efficient than under solar light irradiation. Electrostatic interaction, metal toxicity, and release of singlet oxygen (only in the Cu-doped and Cu/Zn-doped nanocomposites) are the three disinfection mechanisms by which these nanocomposites disinfect water. A regrowth study indicates the absence of any living E. coli cells in treated water even after 4 days. These data and the long hydraulic times (under gravity) exhibited by these nanocomposites during photodisinfection of water indicate an unusually high potential of these nanocomposites as efficient, affordable, and sustainable point-of-use systems for the disinfection of water in developing countries. KW - disinfection KW - nanocomposite material KW - multidrug-resistant Escherichia coli KW - water KW - reactive oxygen species Y1 - 2019 U6 - https://doi.org/10.1021/acsami.9b01212 SN - 1944-8244 SN - 1944-8252 VL - 11 IS - 28 SP - 25483 EP - 25494 PB - American Chemical Society CY - Washington, DC ER - TY - JOUR A1 - Bruun, Kristina A1 - Hille, Carsten T1 - Study on intracellular delivery of liposome encapsulated quantum dots using advanced fluorescence microscopy JF - Scientific reports N2 - Quantum dots increasingly gain popularity for in vivo applications. However, their delivery and accumulation into cells can be challenging and there is still lack of detailed information. Thereby, the application of advanced fluorescence techniques can expand the portfolio of useful parameters for a more comprehensive evaluation. Here, we encapsulated hydrophilic quantum dots into liposomes for studying cellular uptake of these so-called lipodots into living cells. First, we investigated photophysical properties of free quantum dots and lipodots observing changes in the fluorescence decay time and translational diffusion behaviour. In comparison to empty liposomes, lipodots exhibited an altered zeta potential, whereas their hydrodynamic size did not change. Fluorescence lifetime imaging microscopy (FLIM) and fluorescence correlation spectroscopy (FCS), both combined with two-photon excitation (2P), were used to investigate the interaction behaviour of lipodots with an insect epithelial tissue. In contrast to the application of free quantum dots, their successful delivery into the cytosol of salivary gland duct cells could be observed when applying lipodots. Lipodots with different lipid compositions and surface charges did not result in considerable differences in the intracellular labelling pattern, luminescence decay time and diffusion behaviour. However, quantum dot degradation after intracellular accumulation could be assumed from reduced luminescence decay times and blue-shifted luminescence signals. In addition to single diffusing quantum dots, possible intracellular clustering of quantum dots could be assumed from increased diffusion times. Thus, by using a simple and manageable liposome carrier system, 2P-FLIM and 2P-FCS recording protocols could be tested, which are promising for investigating the fate of quantum dots during cellular interaction. Y1 - 2019 U6 - https://doi.org/10.1038/s41598-019-46732-5 SN - 2045-2322 VL - 9 PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Weis, Philipp A1 - Hess, Andreas A1 - Kircher, Gunnar A1 - Huang, Shilin A1 - Auernhammer, Günter K. A1 - Koynov, Kaloian A1 - Butt, Hans-Jürgen A1 - Wu, Si T1 - Effects of Spacers on Photoinduced Reversible Solid-to-Liquid Transitions of Azobenzene-Containing Polymers JF - Chemistry - a European journal N2 - 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. KW - azobenzenes KW - isomerization KW - photochemistry KW - polymers KW - self-healing Y1 - 2019 U6 - https://doi.org/10.1002/chem.201902273 SN - 0947-6539 SN - 1521-3765 VL - 25 IS - 46 SP - 10946 EP - 10953 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Qin, Qing A1 - Zhao, Yun A1 - Schmallegger, Max A1 - Heil, Tobias A1 - Schmidt, Johannes A1 - Walczak, Ralf A1 - Gescheidt-Demner, Georg A1 - Jiao, Haijun A1 - Oschatz, Martin T1 - Enhanced Electrocatalytic N-2 Reduction via Partial Anion Substitution in Titanium Oxide-Carbon Composites JF - Angewandte Chemie : a journal of the Gesellschaft Deutscher Chemiker ; International edition N2 - 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. KW - ammonia synthesis KW - anion substitution KW - MOF-derived catalysts KW - N-2 fixation KW - non-noble metal catalysts Y1 - 2019 U6 - https://doi.org/10.1002/anie.201906056 SN - 1433-7851 SN - 1521-3773 VL - 58 IS - 37 SP - 13101 EP - 13106 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Keller, Sebastian A1 - Wetterhorn, Karl M. A1 - Vecellio, Alison A1 - Seeger, Mark A1 - Rayment, Ivan A1 - Schubert, Torsten T1 - Structural and functional analysis of an l-serine O-phosphate decarboxylase involved in norcobamide biosynthesis JF - FEBS letters : the journal for rapid publication of short reports in molecular biosciences N2 - Structural diversity of natural cobamides (Cbas, B12 vitamers) is limited to the nucleotide loop. The loop is connected to the cobalt‐containing corrin ring via an (R)‐1‐aminopropan‐2‐ol O‐2‐phosphate (AP‐P) linker moiety. AP‐P is produced by the l‐threonine O‐3‐phosphate (l‐Thr‐P) decarboxylase CobD. Here, the CobD homolog SMUL_1544 of the organohalide‐respiring epsilonproteobacterium Sulfurospirillum multivorans was characterized as a decarboxylase that produces ethanolamine O‐phosphate (EA‐P) from l‐serine O‐phosphate (l‐Ser‐P). EA‐P is assumed to serve as precursor of the linker moiety of norcobamides that function as cofactors in the respiratory reductive dehalogenase. SMUL_1544 (SmCobD) is a pyridoxal‐5′‐phosphate (PLP)‐containing enzyme. The structural analysis of the SmCobD apoprotein combined with the characterization of truncated mutant proteins uncovered a role of the SmCobD N‐terminus in efficient l‐Ser‐P conversion. KW - cobamides KW - ethanolamine phosphate KW - norcobamide biosynthesis KW - serine phosphate decarboxylase Y1 - 2019 U6 - https://doi.org/10.1002/1873-3468.13543 SN - 0014-5793 SN - 1873-3468 VL - 593 IS - 21 SP - 3040 EP - 3053 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Alrefai, Anas A1 - Mondal, Suvendu Sekhar A1 - Wruck, Alexander A1 - Kelling, Alexandra A1 - Schilde, Uwe A1 - Brandt, Philipp A1 - Janiak, Christoph A1 - Schoenfeld, Sophie A1 - Weber, Birgit A1 - Rybakowski, Lawrence A1 - Herrman, Carmen A1 - Brennenstuhl, Katlen A1 - Eidner, Sascha A1 - Kumke, Michael Uwe A1 - Behrens, Karsten A1 - Günter, Christina A1 - Müller, Holger A1 - Holdt, Hans-Jürgen T1 - Hydrogen-bonded supramolecular metal-imidazolate frameworks: gas sorption, magnetic and UV/Vis spectroscopic properties JF - Journal of Inclusion Phenomena and Macrocyclic Chemistry N2 - 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. KW - Gas-sorption KW - Ligand design KW - Magnetic properties KW - Supramolecular chemistry KW - Solvothermal synthesis Y1 - 2019 U6 - https://doi.org/10.1007/s10847-019-00926-6 SN - 1388-3127 SN - 1573-1111 VL - 94 IS - 3-4 SP - 155 EP - 165 PB - Springer CY - Dordrecht ER - TY - JOUR A1 - Zhang, Pengfei A1 - Behl, Marc A1 - Peng, Xingzhou A1 - Balk, Maria A1 - Lendlein, Andreas T1 - Chemoresponsive Shape-Memory Effect of Rhodium-Phosphine Coordination Polymer Networks JF - Chemistry of materials : a publication of the American Chemical Society N2 - 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. Y1 - 2019 U6 - https://doi.org/10.1021/acs.chemmater.9b00363 SN - 0897-4756 SN - 1520-5002 VL - 31 IS - 15 SP - 5402 EP - 5407 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Garakani, Tayebeh Mirzaei A1 - Liu, Zhanzhi A1 - Glebe, Ulrich A1 - Gehrmann, Julia A1 - Lazar, Jaroslav A1 - Mertens, Marie Anna Stephanie A1 - Möller, Mieke A1 - Hamzelui, Niloofar A1 - Zhu, Leilei A1 - Schnakenberg, Uwe A1 - Böker, Alexander A1 - Schwaneberg, Ulrich T1 - In Situ Monitoring of Membrane Protein Insertion into Block Copolymer Vesicle Membranes and Their Spreading via Potential-Assisted Approach JF - ACS applied materials & interfaces N2 - 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. KW - synthosomes KW - solid-supported biomimetic membranes KW - polymersome spreading KW - electrochemical impedance spectroscopy KW - FhuA Y1 - 2019 U6 - https://doi.org/10.1021/acsami.9b09302 SN - 1944-8244 SN - 1944-8252 VL - 11 IS - 32 SP - 29276 EP - 29289 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Friess, Fabian A1 - Roch, Toralf A1 - Seifert, Barbara A1 - Lendlein, Andreas A1 - Wischke, Christian T1 - Phagocytosis of spherical and ellipsoidal micronetwork colloids from crosslinked poly(epsilon-caprolactone) JF - International Journal of Pharmaceutics N2 - 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. KW - Particle shape KW - Phagocytosis KW - Macrophage KW - Polymer micronetwork colloids KW - Poly(epsilon-caprolactone) Y1 - 2019 U6 - https://doi.org/10.1016/j.ijpharm.2019.118461 SN - 0378-5173 SN - 1873-3476 VL - 567 PB - Elsevier CY - Amsterdam ER -