TY - JOUR
A1 - Koetz, Joachim
T1 - The Effect of Surface Modification of Gold Nanotriangles for Surface-Enhanced Raman Scattering Performance
JF - Nanomaterials
N2 - A surface modification of ultraflat gold nanotriangles (AuNTs) with different shaped nanoparticles is of special relevance for surface-enhanced Raman scattering (SERS) and the photo-catalytic activity of plasmonic substrates. Therefore, different approaches are used to verify the flat platelet morphology of the AuNTs by oriented overgrowth with metal nanoparticles. The most important part for the morphological transformation of the AuNTs is the coating layer, containing surfactants or polymers. By using well established AuNTs stabilized by a dioctyl sodium sulfosuccinate (AOT) bilayer, different strategies of surface modification with noble metal nanoparticles are possible. On the one hand undulated superstructures were synthesized by in situ growth of hemispherical gold nanoparticles in the polyethyleneimine (PEI)-coated AOT bilayer of the AuNTs. On the other hand spiked AuNTs were obtained by a direct reduction of Au³⁺ ions in the AOT double layer in presence of silver ions and ascorbic acid as reducing agent. Additionally, crumble topping of the smooth AuNTs can be realized after an exchange of the AOT bilayer by hyaluronic acid, followed by a silver-ion mediated reduction with ascorbic acid. Furthermore, a decoration with silver nanoparticles after coating the AOT bilayer with the cationic surfactant benzylhexadecyldimethylammonium chloride (BDAC) can be realized. In that case the ultraviolet (UV)-absorption of the undulated Au@Ag nanoplatelets can be tuned depending on the degree of decoration with silver nanoparticles. Comparing the Raman scattering data for the plasmon driven dimerization of 4-nitrothiophenol (4-NTP) to 4,4′-dimercaptoazobenzene (DMAB) one can conclude that the most important effect of surface modification with a 75 times higher enhancement factor in SERS experiments becomes available by decoration with gold spikes.
KW - undulated
KW - spiked and crumble gold nanotriangles
KW - SERS enhancement factor
KW - dimerization of 4-nitrothiophenol
KW - AOT bilayer
KW - PEI coating
Y1 - 2020
U6 - https://doi.org/10.3390/nano10112187
SN - 2079-4991
VL - 10
IS - 11
PB - MDPI
CY - Basel
ER -
TY - JOUR
A1 - Fudickar, Werner
A1 - Metz, Melanie
A1 - Mai-Linde, Yasemin
A1 - Krüger, Tobias
A1 - Kelling, Alexandra
A1 - Sperlich, Eric
A1 - Linker, Torsten
T1 - Influence of functional groups on the ene reaction of singlet oxygen with 1,4-cyclohexadienes
JF - Photochemistry and photobiology : the official journal of the American Society for Photobiology
N2 - The photooxygenation of 1,4-cyclohexadienes has been studied with a special focus on regio- and stereoselectivities. In all examples, only the methyl-substituted double bond undergoes an ene reaction with singlet oxygen, to afford hydroperoxides in moderate to good yields. We explain the high regioselectivities by a "large-group effect" of the adjacent quaternary stereocenter. Nitriles decrease the reactivity of singlet oxygen, presumably by quenching, but can stabilize proposed per-epoxide intermediates by polar interactions resulting in different stereoselectivities. Spiro lactams and lactones show an interesting effect on regio- and stereoselectivities of the ene reactions. Thus, singlet oxygen attacks the double bond preferentially anti to the carbonyl group, affording only one regioisomeric hydroperoxide. If the reaction occurs from the opposite face, the other regioisomer is exclusively formed by severe electrostatic repulsion in a perepoxide intermediate. We explain this unusual behavior by the fixed geometry of spiro compounds and call it a "spiro effect" in singlet oxygen ene reactions.
Y1 - 2021
U6 - https://doi.org/10.1111/php.13422
SN - 0031-8655
SN - 1751-1097
VL - 97
IS - 6
SP - 1289
EP - 1297
PB - Wiley
CY - Malden, Mass.
ER -
TY - JOUR
A1 - Abbas, Ioana M.
A1 - Vranic, Marija
A1 - Hoffmann, Holger
A1 - El-Khatib, Ahmed H.
A1 - Montes-Bayón, María
A1 - Möller, Heiko Michael
A1 - Weller, Michael G.
T1 - Investigations of the Copper Peptide Hepcidin-25 by
LC-MS/MS and NMR⁺
JF - International Journal of Molecular Sciences
N2 - Hepcidin-25 was identified as themain iron regulator in the human body, and it by binds to the sole iron-exporter ferroportin. Studies showed that the N-terminus of hepcidin is responsible for this interaction, the same N-terminus that encompasses a small copper(II) binding site known as the ATCUN (amino-terminal Cu(II)- and Ni(II)-binding) motif. Interestingly, this copper-binding property is largely ignored in most papers dealing with hepcidin-25. In this context, detailed investigations of the complex formed between hepcidin-25 and copper could reveal insight into its biological role. The present work focuses on metal-bound hepcidin-25 that can be considered the biologically active form. The first part is devoted to the reversed-phase chromatographic separation of copper-bound and copper-free hepcidin-25 achieved by applying basic mobile phases containing 0.1% ammonia. Further, mass spectrometry (tandemmass spectrometry (MS/MS), high-resolutionmass spectrometry (HRMS)) and nuclear magnetic resonance (NMR) spectroscopy were employed to characterize the copper-peptide. Lastly, a three-dimensional (3D)model of hepcidin-25with bound copper(II) is presented. The identification of metal complexes and potential isoforms and isomers, from which the latter usually are left undetected by mass spectrometry, led to the conclusion that complementary analytical methods are needed to characterize a peptide calibrant or referencematerial comprehensively. Quantitative nuclear magnetic resonance (qNMR), inductively-coupled plasma mass spectrometry (ICP-MS), ion-mobility spectrometry (IMS) and chiral amino acid analysis (AAA) should be considered among others.
KW - hepcidin-25
KW - copper
KW - nickel
KW - copper complex
KW - ATCUN motif
KW - metal complex
KW - MS
KW - NMR structure
KW - metal peptide
KW - metalloprotein
KW - metallopeptide
KW - isomerization
KW - racemization
KW - purity
KW - reference material
Y1 - 2018
U6 - https://doi.org/10.3390/ijms19082271
SN - 1422-0067
SN - 1661-6596
VL - 19
IS - 8
PB - Molecular Diversity Preservation International
CY - Basel
ER -
TY - JOUR
A1 - Raju, Rajarshi Roy
A1 - Koetz, Joachim
T1 - Inner rotation of Pickering Janus emulsions
JF - Nanomaterials : open access journal
N2 - Janus droplets were prepared by vortex mixing of three non-mixable liquids, i.e., olive oil, silicone oil and water, in the presence of gold nanoparticles (AuNPs) in the aqueous phase and magnetite nanoparticles (MNPs) in the olive oil. The resulting Pickering emulsions were stabilized by a red-colored AuNP layer at the olive oil/water interface and MNPs at the oil/oil interface. The core–shell droplets can be stimulated by an external magnetic field. Surprisingly, an inner rotation of the silicon droplet is observed when MNPs are fixed at the inner silicon droplet interface. This is the first example of a controlled movement of the inner parts of complex double emulsions by magnetic manipulation via interfacially confined magnetic nanoparticles.
KW - Janus droplets
KW - Pickering emulsions
KW - magnetic manipulation
KW - gold nanoparticles
KW - magnetite nanoparticles
Y1 - 2021
U6 - https://doi.org/10.3390/nano11123312
SN - 2079-4991
VL - 11
IS - 12
PB - MDPI
CY - Basel
ER -
TY - JOUR
A1 - Picconi, David
T1 - Nonadiabatic quantum dynamics of the coherent excited state intramolecular proton transfer of 10-hydroxybenzo[h]quinoline
JF - Photochemical & photobiological sciences
N2 - The photoinduced nonadiabatic dynamics of the enol-keto isomerization of 10-hydroxybenzo[h]quinoline (HBQ) are studied computationally using high-dimensional quantum dynamics. The simulations are based on a diabatic vibronic coupling Hamiltonian, which includes the two lowest pi pi* excited states and a n pi* state, which has high energy in the Franck-Condon zone, but significantly stabilizes upon excited state intramolecular proton transfer. A procedure, applicable to large classes of excited state proton transfer reactions, is presented to parametrize this model using potential energies, forces and force constants, which, in this case, are obtained by time-dependent density functional theory. The wave packet calculations predict a time scale of 10-15 fs for the photoreaction, and reproduce the time constants and the coherent oscillations observed in time- resolved spectroscopic studies performed on HBQ. In contrast to the interpretation given to the most recent experiments, it is found that the reaction initiated by 1 pi pi* <- S-0 photoexcitation proceeds essentially on a single potential energy surface, and the observed coherences bear signatures of Duschinsky mode-mixing along the reaction path. The dynamics after the 2 pi pi* <- S-0 excitation are instead nonadiabatic, and the n pi* state plays a major role in the relaxation process. The simulations suggest a mainly active role of the proton in the isomerization, rather than a passive migration assisted by the vibrations of the benzoquinoline backbone.
[GRAPHICS]
.
KW - Excited state proton transfer
KW - Quantum dynamics
KW - Nonadiabatic effects
KW - Spectroscopy
KW - Coherences
Y1 - 2021
U6 - https://doi.org/10.1007/s43630-021-00112-z
SN - 1474-905X
SN - 1474-9092
VL - 20
IS - 11
SP - 1455
EP - 1473
PB - Springer
CY - Heidelberg
ER -
TY - JOUR
A1 - Zabel, André
A1 - Winter, Alette
A1 - Kelling, Alexandra
A1 - Schilde, Uwe
A1 - Strauch, Peter
T1 - Tetrabromidocuprates(II)-Synthesis, Structure and EPR
JF - International journal of molecular sciences
N2 - Metal-containing ionic liquids (ILs) are of interest for a variety of technical applications, e.g., particle synthesis and materials with magnetic or thermochromic properties. In this paper we report the synthesis of, and two structures for, some new tetrabromidocuprates(II) with several “onium” cations in comparison to the results of electron paramagnetic resonance (EPR) spectroscopic analyses. The sterically demanding cations were used to separate the paramagnetic Cu(II) ions for EPR measurements. The EPR hyperfine structure in the spectra of these new compounds is not resolved, due to the line broadening resulting from magnetic exchange between the still-incomplete separated paramagnetic Cu(II) centres. For the majority of compounds, the principal g values (g|| and gK) of the tensors could be determined and information on the structural changes in the [CuBr4]2- anions can be obtained. The complexes have high potential, e.g., as ionic liquids, as precursors for the synthesis of copper bromide particles, as catalytically active or paramagnetic ionic liquids.
KW - tetrabromidocuprate(II)
KW - X-ray structure
KW - electron paramagnetic resonance
KW - copper(II)
Y1 - 2016
U6 - https://doi.org/10.3390/ijms17040596
VL - 17
IS - 4
PB - MDPI
CY - Basel
ER -
TY - JOUR
A1 - Meyer, S.
A1 - Raber, G.
A1 - Ebert, Franziska
A1 - Leffers, L.
A1 - Müller, Sandra Marie
A1 - Taleshi, M. S.
A1 - Francesconi, Kevin A.
A1 - Schwerdtle, Tanja
T1 - In vitro toxicological characterisation of arsenic-containing fatty acids and three of their metabolites
JF - Toxicology research
N2 - Arsenic-containing fatty acids are a group of fat-soluble arsenic species (arsenolipids) which are present in marine fish and other seafood. Recently, it has been shown that arsenic-containing hydrocarbons, another group of arsenolipids, exert toxicity in similar concentrations comparable to arsenite although the toxic modes of action differ. Hence, a risk assessment of arsenolipids is urgently needed. In this study the cellular toxicity of a saturated (AsFA 362) and an unsaturated (AsFA 388) arsenic-containing fatty acid and three of their proposed metabolites (DMAV, DMAPr and thio-DMAPr) were investigated in human liver cells (HepG2). Even though both arsenic-containing fatty acids were less toxic as compared to arsenic-containing hydrocarbons and arsenite, significant effects were observable at μM concentrations. DMAV causes effects in a similar concentration range and it could be seen that it is metabolised to its highly toxic thio analogue thio-DMAV in HepG2 cells. Nevertheless, DMAPr and thio-DMAPr did not exert any cytotoxicity. In summary, our data indicate that risks to human health related to the presence of arsenic-containing fatty acids in marine food cannot be excluded. This stresses the need for a full in vitro and in vivo toxicological characterisation of these arsenolipids.
Y1 - 2015
U6 - https://doi.org/10.1039/c5tx00122f
SN - 2045-4538
VL - 5
IS - 4
SP - 1289
EP - 1296
PB - Royal Society of Chemistry
CY - Cambridge
ER -
TY - JOUR
A1 - Reschke, Stefan
A1 - Mebs, Stefan
A1 - Sigfridsson-Clauss, Kajsa G. V.
A1 - Kositzki, Ramona
A1 - Leimkühler, Silke
A1 - Haumann, Michael
T1 - Protonation and Sulfido versus Oxo Ligation Changes at the Molybdenum Cofactor in Xanthine Dehydrogenase (XDH) Variants Studied by X-ray Absorption Spectroscopy
JF - Inorganic chemistry
N2 - Enzymes of the xanthine oxidase family are among the best characterized mononuclear molybdenum enzymes. Open questions about their mechanism of transfer of an oxygen atom to the substrate remain. The enzymes share a molybdenum cofactor (Moco) with the metal ion binding a molybdopterin (MPT) molecule via its dithiolene function and terminal sulfur and oxygen groups. For xanthine dehydrogenase (XDH) from the bacterium Rhodobacter capsulatus, we used X-ray absorption spectroscopy to determine the Mo site structure, its changes in a pH range of 5-10, and the influence of amino acids (Glu730 and Gln179) close to Moco in wild-type (WT), Q179A, and E730A variants, complemented by enzyme kinetics and quantum chemical studies. Oxidized WT and Q179A revealed a similar Mo (VI) ion with each one MPT, Mo=O, Mo-O-, and Mo=S ligand, and a weak Mo-O(E730) bond at alkaline pH. Protonation of an oxo to a hydroxo (OH) ligand (pK similar to 6.8) causes inhibition of XDH at acidic pH, whereas deprotonated xanthine (pK similar to 8.8) is an inhibitor at alkaline pH. A similar acidic pK for the WT and Q179A. variants, as well as the metrical parameters of the Mo site and density functional theory calculations, suggested protonation at the equatorial oxo group. The sulfido was replaced with an oxo ligand in the inactive E730A variant, further showing another oxo and one Mo OH ligand at Mo, which are independent of pH. Our findings suggest a reaction mechanism for XDH in which an initial oxo rather than a hydroxo group and the sulfido ligand are essential for xanthine oxidation.
Y1 - 2017
U6 - https://doi.org/10.1021/acs.inorgchem.6b02846
SN - 0020-1669
SN - 1520-510X
VL - 56
IS - 4
SP - 2165
EP - 2176
PB - American Chemical Society
CY - Washington
ER -
TY - JOUR
A1 - Braune, Steffen
A1 - Latour, Robert A.
A1 - Reinthaler, Markus
A1 - Landmesser, Ulf
A1 - Lendlein, Andreas
A1 - Jung, Friedrich
T1 - In Vitro Thrombogenicity Testing of Biomaterials
JF - Advanced healthcare materials
N2 - The short- and long-term thrombogenicity of implant materials is still unpredictable, which is a significant challenge for the treatment of cardiovascular diseases. A knowledge-based approach for implementing biofunctions in materials requires a detailed understanding of the medical device in the biological system. In particular, the interplay between material and blood components/cells as well as standardized and commonly acknowledged in vitro test methods allowing a reproducible categorization of the material thrombogenicity requires further attention. Here, the status of in vitro thrombogenicity testing methods for biomaterials is reviewed, particularly taking in view the preparation of test materials and references, the selection and characterization of donors and blood samples, the prerequisites for reproducible approaches and applied test systems. Recent joint approaches in finding common standards for a reproducible testing are summarized and perspectives for a more disease oriented in vitro thrombogenicity testing are discussed.
KW - biomaterials
KW - blood tests
KW - implants
KW - in vitro
KW - thrombogenicity
Y1 - 2019
U6 - https://doi.org/10.1002/adhm.201900527
SN - 2192-2640
SN - 2192-2659
VL - 8
IS - 21
PB - Wiley
CY - Hoboken
ER -
TY - JOUR
A1 - Lu, Yong-Ping
A1 - Reichetzeder, Christoph
A1 - Prehn, Cornelia
A1 - von Websky, Karoline
A1 - Slowinski, Torsten
A1 - Chen, You-Peng
A1 - Yin, Liang-Hong
A1 - Kleuser, Burkhard
A1 - Yang, Xue-Song
A1 - Adamski, Jerzy
A1 - Hocher, Berthold
T1 - Fetal serum metabolites are independently associated with Gestational diabetes mellitus
JF - Cellular physiology and biochemistry : international journal of experimental cellular physiology, biochemistry and pharmacology
N2 - Background/Aims: Gestational diabetes (GDM) might be associated with alterations in the metabolomic profile of affected mothers and their offspring. Until now, there is a paucity of studies that investigated both, the maternal and the fetal serum metabolome in the setting of GDM. Mounting evidence suggests that the fetus is not just passively affected by gestational disease but might play an active role in it. Metabolomic studies performed in maternal blood and fetal cord blood could help to better discern distinct fetal from maternal disease interactions. Methods: At the time of birth, serum samples from mothers and newborns (cord blood samples) were collected and screened for 163 metabolites utilizing tandem mass spectrometry. The cohort consisted of 412 mother/child pairs, including 31 cases of maternal GDM. Results: An initial non-adjusted analysis showed that eight metabolites in the maternal blood and 54 metabolites in the cord blood were associated with GDM. After Benjamini-Hochberg (BH) procedure and adjustment for confounding factors for GDM, fetal phosphatidylcholine acyl-alkyl C 32:1 and proline still showed an independent association with GDM. Conclusions: This study found metabolites in cord blood which were associated with GDM, even after adjustment for established risk factors of GDM. To the best of our knowledge, this is the first study demonstrating an independent association between fetal serum metabolites and maternal GDM. Our findings might suggest a potential effect of the fetal metabolome on maternal GDM. (c) 2018 The Author(s) Published by S. Karger AG, Basel
KW - Gestational diabetes
KW - Metabolomics
KW - Phosphatidylcholine acyl-alkyl C 32:1
KW - Proline
Y1 - 2018
U6 - https://doi.org/10.1159/000487119
SN - 1015-8987
SN - 1421-9778
VL - 45
IS - 2
SP - 625
EP - 638
PB - Karger
CY - Basel
ER -
TY - JOUR
A1 - López de Guereñu Kurganova, Anna
A1 - Klier, Dennis Tobias
A1 - Haubitz, Toni
A1 - Kumke, Michael Uwe
T1 - Influence of Gd3+ doping concentration on the properties of Na(Y,Gd)F-4
BT - Yb3+, Tm3+ upconverting nanoparticles and their long-term aging behavior
JF - Photochemical & photobiological sciences / European Society for Photobiology
N2 - We present a systematic study on the properties of Na(Y,Gd)F-4-based upconverting nanoparticles (UCNP) doped with 18% Yb3+, 2% Tm3+, and the influence of Gd3+ (10-50 mol% Gd3+). UCNP were synthesized via the solvothermal method and had a range of diameters within 13 and 50 nm. Structural and photophysical changes were monitored for the UCNP samples after a 24-month incubation period in dry phase and further redispersion. Structural characterization was performed by means of X-ray diffraction (XRD), transmission electron microscopy (TEM) as well as dynamic light scattering (DLS), and the upconversion luminescence (UCL) studies were executed at various temperatures (from 4 to 295 K) using time-resolved and steady-state spectroscopy. An increase in the hexagonal lattice phase with the increase of Gd3+ content was found, although the cubic phase was prevalent in most samples. The Tm3+-luminescence intensity as well as the Tm3+-luminescence decay times peaked at the Gd3+ concentration of 30 mol%. Although the general upconverting luminescence properties of the nanoparticles were preserved, the 24-month incubation period lead to irreversible agglomeration of the UCNP and changes in luminescence band ratios and lifetimes.
KW - Upconversion luminescence
KW - Lanthanides
KW - Near infra-red
KW - Ultra-low
KW - temperature
KW - Time-resolved spectroscopy
Y1 - 2022
U6 - https://doi.org/10.1007/s43630-021-00161-4
SN - 1474-905X
SN - 1474-9092
VL - 21
IS - 2
SP - 235
EP - 245
PB - Springer
CY - Heidelberg
ER -
TY - JOUR
A1 - Liu, Yue
A1 - Gould, Oliver E. C.
A1 - Kratz, Karl
A1 - Lendlein, Andreas
T1 - On demand sequential release of (sub)micron particles controlled by size and temperature
JF - Small : nano micro
N2 - Polymeric devices capable of releasing submicron particles (subMP) on demand are highly desirable for controlled release systems, sensors, and smart surfaces. Here, a temperature-memory polymer sheet with a programmable smooth surface served as matrix to embed and release polystyrene subMP controlled by particle size and temperature. subMPs embedding at 80 degrees C can be released sequentially according to their size (diameter D of 200 nm, 500 nm, 1 mu m) when heated. The differences in their embedding extent are determined by the various subMPs sizes and result in their distinct release temperatures. Microparticles of the same size (D approximate to 1 mu m) incorporated in films at different programming temperatures T-p (50, 65, and 80 degrees C) lead to a sequential release based on the temperature-memory effect. The change of apparent height over the film surface is quantified using atomic force microscopy and the realization of sequential release is proven by confocal laser scanning microscopy. The demonstration and quantification of on demand subMP release are of technological impact for assembly, particle sorting, and release technologies in microtechnology, catalysis, and controlled release.
KW - on demand particle release
KW - temperature-memory effect
KW - thermosensitive
KW - polymer surface
Y1 - 2022
U6 - https://doi.org/10.1002/smll.202104621
SN - 1613-6810
SN - 1613-6829
VL - 18
IS - 5
PB - Wiley-VCH
CY - Weinheim
ER -
TY - JOUR
A1 - Deng, Zijun
A1 - Zou, Jie
A1 - Wang, Weiwei
A1 - Nie, Yan
A1 - Tung, Wing-Tai
A1 - Ma, Nan
A1 - Lendlein, Andreas
T1 - Dedifferentiation of mature adipocytes with periodic exposure to cold
JF - Clinical hemorheology and microcirculation : blood flow and vessels
N2 - 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.
KW - Adipocyte
KW - dedifferentiation
KW - cold
KW - lipid
Y1 - 2019
U6 - https://doi.org/10.3233/CH-199005
SN - 1386-0291
SN - 1875-8622
VL - 71
IS - 4
SP - 415
EP - 424
PB - IOS Press
CY - Amsterdam
ER -
TY - JOUR
A1 - Ebel, Kenny
A1 - Bald, Ilko
T1 - Length and Energy Dependence of Low-Energy Electron-Induced Strand Breaks in Poly(A) DNA
JF - International Journal of Molecular Sciences
N2 - The DNA in living cells can be effectively damaged by high-energy radiation, which can lead to cell death. Through the ionization of water molecules, highly reactive secondary species such as low-energy electrons (LEEs) with the most probable energy around 10 eV are generated, which are able to induce DNA strand breaks via dissociative electron attachment. Absolute DNA strand break cross sections of specific DNA sequences can be efficiently determined using DNA origami nanostructures as platforms exposing the target sequences towards LEEs. In this paper, we systematically study the effect of the oligonucleotide length on the strand break cross section at various irradiation energies. The present work focuses on poly-adenine sequences (d(A₄), d(A₈), d(A₁₂), d(A₁₆), and d(A₂₀)) irradiated with 5.0, 7.0, 8.4, and 10 eV electrons. Independent of the DNA length, the strand break cross section shows a maximum around 7.0 eV electron energy for all investigated oligonucleotides confirming that strand breakage occurs through the initial formation of negative ion resonances. When going from d(A₄) to d(A₁₆), the strand break cross section increases with oligonucleotide length, but only at 7.0 and 8.4 eV, i.e., close to the maximum of the negative ion resonance, the increase in the strand break cross section with the length is similar to the increase of an estimated geometrical cross section. For d(A₂₀), a markedly lower DNA strand break cross section is observed for all electron energies, which is tentatively ascribed to a conformational change of the dA₂₀ sequence. The results indicate that, although there is a general length dependence of strand break cross sections, individual nucleotides do not contribute independently of the absolute strand break cross section of the whole DNA strand. The absolute quantification of sequence specific strand breaks will help develop a more accurate molecular level understanding of radiation induced DNA damage, which can then be used for optimized risk estimates in cancer radiation therapy.
KW - DNA origami
KW - DNA radiation damage
KW - DNA strand breaks
KW - low-energy electrons
KW - sequence dependence
Y1 - 2019
U6 - https://doi.org/10.3390/ijms21010111
SN - 1422-0067
VL - 21
IS - 1
PB - Molecular Diversity Preservation International
CY - Basel
ER -
TY - THES
A1 - Nacak, Selma
T1 - Synthesis and Characterization of Upconversion Nanaparticles for Applications in Life Sciences
Y1 - 2021
ER -
TY - JOUR
A1 - Neffe, Axel T.
A1 - Izraylit, Victor
A1 - Hommes-Schattmann, Paul J.
A1 - Lendlein, Andreas
T1 - Soft, formstable (Co)polyester blend elastomers
JF - Nanomaterials : open access journal
N2 - High crystallization rate and thermomechanical stability make polylactide stereocomplexes effective nanosized physical netpoints. Here, we address the need for soft, form-stable degradable elastomers for medical applications by designing such blends from (co)polyesters, whose mechanical properties are ruled by their nanodimensional architecture and which are applied as single components in implants. By careful controlling of the copolymer composition and sequence structure of poly[(L-lactide)-co-(epsilon-caprolactone)], it is possible to prepare hyperelastic polymer blends formed through stereocomplexation by adding poly(D-lactide) (PDLA). Low glass transition temperature T-g <= 0 degrees C of the mixed amorphous phase contributes to the low Young's modulus E. The formation of stereocomplexes is shown in DSC by melting transitions T-m > 190 degrees C and in WAXS by distinct scattering maxima at 2 theta = 12 degrees and 21 degrees. Tensile testing demonstrated that the blends are soft (E = 12-80 MPa) and show an excellent hyperelastic recovery R-rec = 66-85% while having high elongation at break epsilon(b) up to >1000%. These properties of the blends are attained only when the copolymer has 56-62 wt% lactide content, a weight average molar mass >140 kg center dot mol(-1), and number average lactide sequence length >= 4.8, while the blend is formed with a content of 5-10 wt% of PDLA. The devised strategy to identify a suitable copolymer for stereocomplexation and blend formation is transferable to further polymer systems and will support the development of thermoplastic elastomers suitable for medical applications.
KW - thermoplastic elastomer
KW - biomaterial
KW - stereocomplexes
KW - mechanical
KW - properties
KW - form stability
KW - crystallinity
Y1 - 2021
U6 - https://doi.org/10.3390/nano11061472
SN - 2079-4991
VL - 11
IS - 6
PB - MDPI
CY - Basel
ER -
TY - JOUR
A1 - Bhuvanesh, Thanga
A1 - Machatschek, Rainhard Gabriel
A1 - Lysyakova, Liudmila
A1 - Kratz, Karl
A1 - Schulz, Burkhard
A1 - Ma, Nan
A1 - Lendlein, Andreas
T1 - Collagen type-IV Langmuir and Langmuir-Schafer layers as model biointerfaces to direct stem cell adhesion
JF - Biomedical materials : materials for tissue engineering and regenerative medicine
N2 - 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.
KW - collagen-IV
KW - basement membrane
KW - Langmuir-Schafer films
KW - stem cell adhesion
KW - protein
KW - ellipsometry
Y1 - 2019
U6 - https://doi.org/10.1088/1748-605X/aaf464
SN - 1748-6041
SN - 1748-605X
VL - 14
IS - 2
PB - Inst. of Physics Publ.
CY - Bristol
ER -
TY - JOUR
A1 - Fudickar, Werner
A1 - Roder, Phillip
A1 - Listek, Martin
A1 - Hanack, Katja
A1 - Linker, Torsten
T1 - Pyridinium alkynylanthracenes as sensitizers for photodynamic therapy
JF - Photochemistry and photobiology
N2 - Photodynamic therapy (PDT) is a mild but effective method to treat certain types of cancer upon irradiation with visible light. Here, three isomeric methylpyridinium alkynylanthracenes 1op were evaluated as sensitizers for PDT. Upon irradiation with blue or green light, all three compounds show the ability to initiate strand breaks of plasmid DNA. The mayor species responsible for cleavage is singlet oxygen (O-1(2)) as confirmed by scavenging reagents. Only isomers 1m and 1p can be incorporated into HeLa cells, whereas isomer 1o cannot permeate through the membrane. While isomer 1m targets the cell nucleus, isomer 1p assembles in the cellular cytoplasm and impacts the cellular integrity. This is in accordance with a moderate toxicity of 1p in the dark, whereas 1m exhibits no dark toxicity. Both isomers are suitable as PDT reagents, with a CC50 of 3 mu m and 75 nm, for 1p and 1m, respectively. Thus, derivative 1m, which can be easily synthesized, becomes an interesting candidate for cancer therapy.
Y1 - 2021
U6 - https://doi.org/10.1111/php.13554
SN - 0031-8655
SN - 1751-1097
VL - 98
IS - 1
SP - 193
EP - 201
PB - Wiley
CY - Hoboken
ER -
TY - JOUR
A1 - Niedl, Robert Raimund
A1 - Beta, Carsten
T1 - Hydrogel-driven paper-based microfluidics
JF - LAB on a chip : miniaturisation for chemistry and biology
N2 - Paper-based microfluidics provide an inexpensive, easy to use technology for point-of-care diagnostics in developing countries. Here, we combine paper-based microfluidic devices with responsive hydrogels to add an entire new class of functions to these versatile low-cost fluidic systems. The hydrogels serve as fluid reservoirs. In response to an external stimulus, e.g. an increase in temperature, the hydrogels collapse and release fluid into the structured paper substrate. In this way, chemicals that are either stored on the paper substrate or inside the hydrogel pads can be dissolved, premixed, and brought to reaction to fulfill specific analytic tasks. We demonstrate that multi-step sequences of chemical reactions can be implemented in a paper-based system and operated without the need for external precision pumps. We exemplify this technology by integrating an antibody-based E. coli test on a small and easy to use paper device.
Y1 - 2015
U6 - https://doi.org/10.1039/c5lc00276a
SN - 1473-0197
SN - 1473-0189
VL - 11
IS - 15
SP - 2452
EP - 2459
PB - Royal Society of Chemistry
CY - Cambridge
ER -
TY - JOUR
A1 - Wang, Xuepu
A1 - Sperling, Marcel
A1 - Reifarth, Martin
A1 - Böker, Alexander
T1 - Shaping metallic nanolattices
BT - Design by microcontact printing from wrinkled stamps
JF - Small
N2 - A method for the fabrication of well-defined metallic nanostructures is presented here in a simple and straightforward fashion. As an alternative to lithographic techniques, this routine employs microcontact printing utilizing wrinkled stamps, which are prepared from polydimethylsiloxane (PDMS), and includes the formation of hydrophobic stripe patterns on a substrate via the transfer of oligomeric PDMS. Subsequent backfilling of the interspaces between these stripes with a hydroxyl-functional poly(2-vinyl pyridine) then provides the basic pattern for the deposition of citrate-stabilized gold nanoparticles promoted by electrostatic interaction. The resulting metallic nanostripes can be further customized by peeling off particles in a second microcontact printing step, which employs poly(ethylene imine) surface-decorated wrinkled stamps, to form nanolattices. Due to the independent adjustability of the period dimensions of the wrinkled stamps and stamp orientation with respect to the substrate, particle arrays on the (sub)micro-scale with various kinds of geometries are accessible in a straightforward fashion. This work provides an alternative, cost-effective, and scalable surface-patterning technique to fabricate nanolattice structures applicable to multiple types of functional nanoparticles. Being a top-down method, this process could be readily implemented into, e.g., the fabrication of optical and sensing devices on a large scale.
KW - gold nanoparticle assembly
KW - hydroxyl-functional poly(2-vinyl pyridine)
KW - metallic nanolattices
KW - microcontact printing
KW - oligomeric
KW - polydimethylsiloxane
KW - polydimethylsiloxane wrinkles
KW - wrinkled stamps
Y1 - 2020
U6 - https://doi.org/10.1002/smll.201906721
SN - 1613-6810
SN - 1613-6829
VL - 16
IS - 11
SP - 1
EP - 8
PB - Wiley-VCH
CY - Weinheim
ER -