TY - JOUR A1 - Liebig, Ferenc A1 - Sarhan, Radwan Mohamed A1 - Prietzel, Claudia Christina A1 - Thünemann, Andreas F. A1 - Bargheer, Matias A1 - Koetz, Joachim T1 - Undulated Gold Nanoplatelet Superstructures BT - In Situ Growth of Hemispherical Gold Nanoparticles onto the Surface of Gold Nanotriangles JF - Langmuir N2 - Negatively charged flat gold nanotriangles, formed in a vesicular template phase and separated by an AOT-micelle-based depletion flocculation, were reloaded by adding a cationic polyelectrolyte, that is, a hyperbranched polyethylenimine (PEI). Heating the system to 100 degrees C in the presence of a gold chloride solution, the reduction process leads to the formation of gold nanoparticles inside the polymer shell surrounding the nanoplatelets. The gold nanoparticle formation is investigated by UV-vis spectroscopy, small-angle X-ray scattering, and dynamic light scattering measurements in combination with transmission electron microscopy. Spontaneously formed gold clusters in the hyperbranched PEI shell with an absorption maximum at 350 nm grow on the surface of the nanotriangles as hemispherical particles with diameters of similar to 6 nm. High-resolution micrographs show that the hemispherical gold particles are crystallized onto the {111} facets on the bottom and top of the platelet as well as on the edges without a grain boundary. Undulated gold nanoplatelet superstructures with special properties become available, which show a significantly modified performance in SERS-detected photocatalysis regarding both reactivity and enhancement factor. Y1 - 2018 U6 - https://doi.org/10.1021/acs.langmuir.7b02898 SN - 0743-7463 VL - 34 IS - 15 SP - 4584 EP - 4594 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Liebig, Ferenc A1 - Thünemann, Andreas F. A1 - Koetz, Joachim T1 - Ostwald Ripening Growth Mechanism of Gold Nanotriangles in Vesicular Template Phases JF - Langmuir N2 - The mechanism of nanotriangle formation in multivesicular vesicles (MMV) is investigated by using time-dependent SAXS measurements in combination with UV-vis spectroscopy, light, and transmission electron microscopy. In the first time period 6.5 nm sized spherical gold nanoparticles are formed inside of the vesicles, which build up soft nanoparticle aggregates. a) In situ SAXS experiments show a linear increase of the volume and molar mass of nanotriangles in the second time period. The volume growth rate of the triangles is 16.1 nm(3)/min, and the growth rate in the vertical direction is only 0.02 nm/min. Therefore, flat nanotriangles with a thickness of 7 nm and a diameter of 23 nm are formed. This process can be described by a diffusion limited Ostwald ripening growth mechanism. TEM micrographs visualize soft coral-like structures with thin nanoplatelets at the periphery of the aggregates, which disaggregate in the third time period into nanotriangles and spherical particles. The 16 times faster growth of nanotriangles in the lateral than that in the vertical direction is related to the adsorption of symmetry breaking components, i.e., AOT and the polyampholyte PalPhBisCarb, on the {111} facets of the gold nanoplatelets in combination with confinement effects of the vesicular template phase. Y1 - 2016 U6 - https://doi.org/10.1021/acs.langmuir.6b02662 SN - 0743-7463 VL - 32 SP - 10928 EP - 10935 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Wessig, Pablo A1 - Budach, Dennis B. A1 - Thünemann, Andreas F. T1 - Dendrimers with Oligospiroketal (OSK) Building Blocks: Synthesis and Properties JF - Chemistry - a European journal N2 - The development of novel dendrimers containing oligospiroketal (OSK) rods as building blocks is described. The linkage between the core unit (CU), branching units (BU), and OSK rods relies on the CuAAC reaction between terminal alkynes and azides. Two different strategies of dendrimer synthesis were investigated and it was found that the convergent approach is clearly superior to the divergent one. SAXS measurements and MD simulations indicate that the obtained dendrimer features a globular structure with very low density. Obviously, the OSK rods stabilize a rather loose mass-fractal structure. KW - click chemistry KW - dendrimers KW - molecular rods KW - oxygen heterocycles KW - SAXS Y1 - 2015 U6 - https://doi.org/10.1002/chem.201501386 SN - 0947-6539 SN - 1521-3765 VL - 21 IS - 29 SP - 10466 EP - 10471 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Leiterer, York A1 - Leitenberger, Wolfram A1 - Emmerling, Franziska A1 - Thünemann, Andreas F. A1 - Panne, Ulrich T1 - The use of an acoustic levitator to follow crystallization in small droplets by energydispersive X-ray diffraction Y1 - 2006 UR - http://journals.iucr.org/j/issues/2006/05/00/wf5016/wf5016.pdf U6 - https://doi.org/10.1107/S0021889806024915 SN - 0021-8898 ER - TY - JOUR A1 - Pietsch, Ullrich A1 - Kubowicz, Stephan A1 - Thünemann, Andreas F. A1 - Geue, Thomas A1 - Watson, M. D. A1 - Tchebotareva, N. A1 - Müllen, K. T1 - X-ray reflectivity study of an amphiphilic hex-peri-hexabenzocoronene at a structured silicon wafer surface Y1 - 2003 ER - TY - JOUR A1 - Kubowicz, Stephan A1 - Baussard, Jean-Francois A1 - Lutz, Jean-Francois A1 - Thünemann, Andreas F. A1 - von Berlepsch, Hans A1 - Laschewsky, André T1 - Multicompartment micelles formed by self-assembly of linear ABC triblock copolymers in aqueous medium Y1 - 2005 ER - TY - JOUR A1 - Thünemann, Andreas F. A1 - Kubowicz, Stephan A1 - Pietsch, Ullrich T1 - Ultra-thin solid polyelectrolyte-surfactant complex films : structure and wetting Y1 - 2000 ER - TY - THES A1 - Thünemann, Andreas F. T1 - Self-assembly, ordered nanostructures and functionality of polyelectrolyte-amphiphile complexes Y1 - 2000 ER - TY - JOUR A1 - Fortes Martín, Rebeca A1 - Thünemann, Andreas F. A1 - Stockmann, Jörg M. A1 - Radnik, Jörg A1 - Koetz, Joachim T1 - From nanoparticle heteroclusters to filament networks by self-assembly at the water-oil interface of reverse microemulsions JF - Langmuir : the ACS journal of surfaces and colloids / American Chemical Society N2 - Surface self-assembly of spherical nanoparticles of sizes below 10 nm into hierarchical heterostructures is under arising development despite the inherent difficulties of obtaining complex ordering patterns on a larger scale. Due to template-mediated interactions between oil-dispersible superparamagnetic nanoparticles (MNPs) and polyethylenimine- stabilized gold nanoparticles (Au(PEI)NPs) at the water-oil interface of microemulsions, complex nanostructured films can be formed. Characterization of the reverse microemulsion phase by UV-vis absorption revealed the formation of heteroclusters from Winsor type II phases (WPII) using Aerosol-OT (AOT) as the surfactant. SAXS measurements verify the mechanism of initial nanoparticle clustering in defined dimensions. XPS suggested an influence of AOT at the MNP surface. Further, cryo-SEM and TEM visualization demonstrated the elongation of the reverse microemulsions into cylindrical, wormlike structures, which subsequently build up larger nanoparticle superstructure arrangements. Such WPII phases are thus proven to be a new form of soft template, mediating the self-assembly of different nanoparticles in hierarchical network-like filaments over a substrate during solvent evaporation. KW - Emulsions KW - Liquids KW - Nanoparticles KW - Water KW - X-ray scattering Y1 - 2021 U6 - https://doi.org/10.1021/acs.langmuir.1c01348 SN - 0743-7463 VL - 37 IS - 29 SP - 8876 EP - 8885 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Liebig, Ferenc A1 - Sarhan, Radwan Mohamed A1 - Schmitt, Clemens Nikolaus Zeno A1 - Thünemann, Andreas F. A1 - Prietzel, Claudia Christina A1 - Bargheer, Matias A1 - Koetz, Joachim T1 - Gold nanotriangles with crumble topping and their influence on catalysis and surface-enhanced raman spectroscopy JF - ChemPlusChem N2 - By adding hyaluronic acid (HA) to dioctyl sodium sulfosuccinate (AOT)-stabilized gold nanotriangles (AuNTs) with an average thickness of 7.5 +/- 1 nm and an edge length of about 175 +/- 17 nm, the AOT bilayer is replaced by a polymeric HA-layer leading to biocompatible nanoplatelets. The subsequent reduction process of tetrachloroauric acid in the HA-shell surrounding the AuNTs leads to the formation of spherical gold nanoparticles on the platelet surface. With increasing tetrachloroauric acid concentration, the decoration with gold nanoparticles can be tuned. SAXS measurements reveal an increase of the platelet thickness up to around 14.5 nm, twice the initial value of bare AuNTs. HRTEM micrographs show welding phenomena between densely packed particles on the platelet surface, leading to a crumble formation while preserving the original crystal structure. Crumbles crystallized on top of the platelets enhance the Raman signal by a factor of around 20, and intensify the plasmon-driven dimerization of 4-nitrothiophenol (4-NTP) to 4,4 '-dimercaptoazobenzene in a yield of up to 50 %. The resulting crumbled nanotriangles, with a biopolymer shell and the absorption maximum in the second window for in vivo imaging, are promising candidates for biomedical sensing. KW - gold nanostructures KW - HRTEM KW - hyaluronic acid KW - monolayer formation KW - SERS Y1 - 2020 U6 - https://doi.org/10.1002/cplu.201900745 SN - 2192-6506 VL - 85 IS - 3 SP - 519 EP - 526 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Neffe, Axel T. A1 - von Rüsten-Lange, Maik A1 - Braune, Steffen A1 - Lützow, Karola A1 - Roch, Toralf A1 - Richau, Klaus A1 - Krüger, Anne A1 - Becherer, Tobias A1 - Thünemann, Andreas F. A1 - Jung, Friedrich A1 - Haag, Rainer A1 - Lendlein, Andreas T1 - Multivalent grafting of hyperbranched oligo- and polyglycerols shielding rough membranes to mediate hemocompatibility JF - Journal of materials chemistry : B, Materials for biology and medicine N2 - Hemocompatible materials are needed for internal and extracorporeal biomedical applications, which should be realizable by reducing protein and thrombocyte adhesion to such materials. Polyethers have been demonstrated to be highly efficient in this respect on smooth surfaces. Here, we investigate the grafting of oligo- and polyglycerols to rough poly(ether imide) membranes as a polymer relevant to biomedical applications and show the reduction of protein and thrombocyte adhesion as well as thrombocyte activation. It could be demonstrated that, by performing surface grafting with oligo-and polyglycerols of relatively high polydispersity (>1.5) and several reactive groups for surface anchoring, full surface shielding can be reached, which leads to reduced protein adsorption of albumin and fibrinogen. In addition, adherent thrombocytes were not activated. This could be clearly shown by immunostaining adherent proteins and analyzing the thrombocyte covered area. The presented work provides an important strategy for the development of application relevant hemocompatible 3D structured materials. Y1 - 2014 U6 - https://doi.org/10.1039/c4tb00184b SN - 2050-750X SN - 2050-7518 VL - 2 IS - 23 SP - 3626 EP - 3635 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Ihlenburg, Ramona A1 - Mai, Tobias A1 - Thünemann, Andreas F. A1 - Baerenwald, Ruth A1 - Saalwächter, Kay A1 - Koetz, Joachim A1 - Taubert, Andreas T1 - Sulfobetaine hydrogels with a complex multilength-scale hierarchical structure JF - The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces & biophysical chemistry N2 - Hydrogels with a hierarchical structure were prepared from a new highly water-soluble crosslinker N,N,N',N'-tetramethyl-N,N'-bis(2-ethylmethacrylate)-propyl-1,3-diammonium dibromide and from the sulfobetaine monomer 2-(N-3-sulfopropyl-N,N-dimethyl ammonium)ethyl methacrylate. The free radical polymerization of the two compounds is rapid and yields near-transparent hydrogels with sizes up to 5 cm in diameter. Rheology shows a clear correlation between the monomer-to-crosslinker ratio and the storage and loss moduli of the hydrogels. Cryo-scanning electron microscopy, low-field nuclear magnetic resonance (NMR) spectroscopy, and small-angle X-ray scattering show that the gels have a hierarchical structure with features spanning the nanometer to the sub-millimeter scale. The NMR study is challenged by the marked inhomogeneity of the gels and the complex chemical structure of the sulfobetaine monomer. NMR spectroscopy shows how these complications can be addressed via a novel fitting approach that considers the mobility gradient along the side chain of methacrylate-based monomers. KW - Defects KW - Hydrogels KW - Nuclear magnetic resonance spectroscopy KW - Scattering KW - X-ray scattering Y1 - 2021 U6 - https://doi.org/10.1021/acs.jpcb.0c10601 SN - 1520-6106 SN - 1520-5207 VL - 125 IS - 13 SP - 3398 EP - 3408 PB - American Chemical Society CY - Washington ER - TY - GEN A1 - Neffe, Axel T. A1 - von Rüsten-Lange, Maik A1 - Braune, Steffen A1 - Lützow, Karola A1 - Roch, Toralf A1 - Richau, Klaus A1 - Krüger, Anne A1 - Becherer, Tobias A1 - Thünemann, Andreas F. A1 - Jung, Friedrich A1 - Haag, Rainer A1 - Lendlein, Andreas T1 - Multivalent grafting of hyperbranched oligo- and polyglycerols shielding rough membranes to mediate hemocompatibility N2 - Hemocompatible materials are needed for internal and extracorporeal biomedical applications, which should be realizable by reducing protein and thrombocyte adhesion to such materials. Polyethers have been demonstrated to be highly efficient in this respect on smooth surfaces. Here, we investigate the grafting of oligo- and polyglycerols to rough poly(ether imide) membranes as a polymer relevant to biomedical applications and show the reduction of protein and thrombocyte adhesion as well as thrombocyte activation. It could be demonstrated that, by performing surface grafting with oligo- and polyglycerols of relatively high polydispersity (>1.5) and several reactive groups for surface anchoring, full surface shielding can be reached, which leads to reduced protein adsorption of albumin and fibrinogen. In addition, adherent thrombocytes were not activated. This could be clearly shown by immunostaining adherent proteins and analyzing the thrombocyte covered area. The presented work provides an important strategy for the development of application relevant hemocompatible 3D structured materials. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 285 Y1 - 2014 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-99444 ER - TY - JOUR A1 - Haase, Andrea A1 - Rott, Stephanie A1 - Mantion, Alexandre A1 - Graf, Philipp A1 - Plendl, Johanna A1 - Thünemann, Andreas F. A1 - Meier, Wolfgang P. A1 - Taubert, Andreas A1 - Luch, Andreas A1 - Reiser, Georg T1 - Effects of silver nanoparticles on primary mixed neural cell cultures: Uptake, oxidative stress and acute calcium responses JF - Toxicological sciences N2 - In the body, nanoparticles can be systemically distributed and then may affect secondary target organs, such as the central nervous system (CNS). Putative adverse effects on the CNS are rarely investigated to date. Here, we used a mixed primary cell model consisting mainly of neurons and astrocytes and a minor proportion of oligodendrocytes to analyze the effects of well-characterized 20 and 40 nm silver nanoparticles (SNP). Similar gold nanoparticles served as control and proved inert for all endpoints tested. SNP induced a strong size-dependent cytotoxicity. Additionally, in the low concentration range (up to 10 mu g/ml of SNP), the further differentiated cultures were more sensitive to SNP treatment. For detailed studies, we used low/medium dose concentrations (up to 20 mu g/ml) and found strong oxidative stress responses. Reactive oxygen species (ROS) were detected along with the formation of protein carbonyls and the induction of heme oxygenase-1. We observed an acute calcium response, which clearly preceded oxidative stress responses. ROS formation was reduced by antioxidants, whereas the calcium response could not be alleviated by antioxidants. Finally, we looked into the responses of neurons and astrocytes separately. Astrocytes were much more vulnerable to SNP treatment compared with neurons. Consistently, SNP were mainly taken up by astrocytes and not by neurons. Immunofluorescence studies of mixed cell cultures indicated stronger effects on astrocyte morphology. Altogether, we can demonstrate strong effects of SNP associated with calcium dysregulation and ROS formation in primary neural cells, which were detectable already at moderate dosages. KW - silver nanoparticles KW - neurons KW - oxidative stress KW - protein carbonyls KW - calcium Y1 - 2012 U6 - https://doi.org/10.1093/toxsci/kfs003 SN - 1096-6080 VL - 126 IS - 2 SP - 457 EP - 468 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Haase, A. A1 - Mantion, A. A1 - Graf, P. A1 - Plendl, J. A1 - Thünemann, Andreas F. A1 - Meier, Wolfgang P. A1 - Taubert, Andreas A1 - Luch, A. T1 - A novel type of silver nanoparticles and their advantages in toxicity testing in cell culture systems JF - Archives of toxicology : official journal of EUROTOX N2 - Silver nanoparticles (SNPs) are among the most commercialized nanoparticles worldwide. Often SNP are used because of their antibacterial properties. Besides that they possess unique optic and catalytic features, making them highly interesting for the creation of novel and advanced functional materials. Despite its widespread use only little data exist in terms of possible adverse effects of SNP on human health. Conventional synthesis routes usually yield products of varying quality and property. It thus may become puzzling to compare biological data from different studies due to the great variety in sizes, coatings or shapes of the particles applied. Here, we applied a novel synthesis approach to obtain SNP of well-defined colloidal and structural properties. Being stabilized by a covalently linked small peptide, these particles are nicely homogenous, with narrow size distribution, and form monodisperse suspensions in aqueous solutions. We applied these peptide-coated SNP in two different sizes of 20 or 40 nm (Ag20Pep and Ag40Pep) and analyzed responses of THP-1-derived human macrophages while being exposed against these particles. Gold nanoparticles of similar size and coating (Au20Pep) were used for comparison. The cytotoxicity of particles was assessed by WST-1 and LDH assays, and the uptake into the cells was confirmed via transmission electron microscopy. In summary, our data demonstrate that this novel type of SNP is well suited to serve as model system for nanoparticles to be tested in toxicological studies in vitro. KW - Silver nanoparticles KW - Peptide coating KW - Nanotoxicity Y1 - 2012 U6 - https://doi.org/10.1007/s00204-012-0836-0 SN - 0340-5761 VL - 86 IS - 7 SP - 1089 EP - 1098 PB - Springer CY - Heidelberg ER - TY - JOUR A1 - Casse, Olivier A1 - Shkilnyy, Andriy A1 - Linders, Jürgen A1 - Mayer, Christian A1 - Häussinger, Daniel A1 - Völkel, Antje A1 - Thünemann, Andreas F. A1 - Dimova, Rumiana A1 - Cölfen, Helmut A1 - Meier, Wolfgang P. A1 - Schlaad, Helmut A1 - Taubert, Andreas T1 - Solution behavior of double-hydrophilic block copolymers in dilute aqueous solution JF - Macromolecules : a publication of the American Chemical Society N2 - The self-assembly of double-hydrophilic poly(ethylene oxide)-poly(2-methyl-2-oxazoline) diblock copolymers in water has been studied. Isothermal titration calorimetry, small-angle X-ray scattering, and analytical ultracentrifugation suggest that only single polymer chains are present in solution. In contrast, light scattering and transmission electron microscopy detect aggregates with radii of ca. 100 nm. Pulsed field gradient NMR spectroscopy confirms the presence of aggregates, although only 2% of the polymer chains undergo aggregation. Water uptake experiments indicate differences in the hydrophilicity of the two blocks, which is believed to be the origin of the unexpected aggregation behavior (in accordance with an earlier study by Ke et al. [Macromolecules 2009, 42, 5339-5344]). The data therefore suggest that even in double-hydrophilic block copolymers, differences in hydrophilicity are sufficient to drive polymer aggregation, a phenomenon that has largely been overlooked or ignored so far. Y1 - 2012 U6 - https://doi.org/10.1021/ma300621g SN - 0024-9297 VL - 45 IS - 11 SP - 4772 EP - 4777 PB - American Chemical Society CY - Washington ER -