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Effects of silver nanoparticles on primary mixed neural cell cultures: Uptake, oxidative stress and acute calcium responses (2012)
Haase, Andrea ; Rott, Stephanie ; Mantion, Alexandre ; Graf, Philipp ; Plendl, Johanna ; Thünemann, Andreas F. ; Meier, Wolfgang P. ; Taubert, Andreas ; Luch, Andreas ; Reiser, Georg
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.
Solution behavior of double-hydrophilic block copolymers in dilute aqueous solution (2012)
Casse, Olivier ; Shkilnyy, Andriy ; Linders, Jürgen ; Mayer, Christian ; Häussinger, Daniel ; Völkel, Antje ; Thünemann, Andreas F. ; Dimova, Rumiana ; Cölfen, Helmut ; Meier, Wolfgang P. ; Schlaad, Helmut ; Taubert, Andreas
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.
Multivalent grafting of hyperbranched oligo- and polyglycerols shielding rough membranes to mediate hemocompatibility (2014)
Neffe, Axel T. ; von Rüsten-Lange, Maik ; Braune, Steffen ; Lützow, Karola ; Roch, Toralf ; Richau, Klaus ; Krüger, Anne ; Becherer, Tobias ; Thünemann, Andreas F. ; Jung, Friedrich ; Haag, Rainer ; Lendlein, Andreas
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.
Multivalent grafting of hyperbranched oligo- and polyglycerols shielding rough membranes to mediate hemocompatibility (2014)
Neffe, Axel T. ; von Rüsten-Lange, Maik ; Braune, Steffen ; Lützow, Karola ; Roch, Toralf ; Richau, Klaus ; Krüger, Anne ; Becherer, Tobias ; Thünemann, Andreas F. ; Jung, Friedrich ; Haag, Rainer ; Lendlein, Andreas
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.
Self-assembly, ordered nanostructures and functionality of polyelectrolyte-amphiphile complexes (2000)
Thünemann, Andreas F.
Ultra-thin solid polyelectrolyte-surfactant complex films : structure and wetting (2000)
Thünemann, Andreas F. ; Kubowicz, Stephan ; Pietsch, Ullrich
Unique properties of eukaryote-type actin and profilin horizontally transferred to cyanobacteria (2012)
Guljamow, Arthur ; Delissen, Friedmar ; Baumann, Otto ; Thuenemann, Andreas F. ; Dittmann-Thünemann, Elke
A eukaryote-type actin and its binding protein profilin encoded on a genomic island in the cyanobacterium Microcystis aeruginosa PCC 7806 co-localize to form a hollow, spherical enclosure occupying a considerable intracellular space as shown by in vivo fluorescence microscopy. Biochemical and biophysical characterization reveals key differences between these proteins and their eukaryotic homologs. Small-angle X-ray scattering shows that the actin assembles into elongated, filamentous polymers which can be visualized microscopically with fluorescent phalloidin. Whereas rabbit actin forms thin cylindrical filaments about 100 mu m in length, cyanobacterial actin polymers resemble a ribbon, arrest polymerization at 510 lam and tend to form irregular multi-strand assemblies. While eukaryotic profilin is a specific actin monomer binding protein, cyanobacterial profilin shows the unprecedented property of decorating actin filaments. Electron micrographs show that cyanobacterial profilin stimulates actin filament bundling and stabilizes their lateral alignment into heteropolymeric sheets from which the observed hollow enclosure may be formed. We hypothesize that adaptation to the confined space of a bacterial cell devoid of binding proteins usually regulating actin polymerization in eukaryotes has driven the co-evolution of cyanobacterial actin and profilin, giving rise to an intracellular entity.
Dendrimers with Oligospiroketal (OSK) Building Blocks: Synthesis and Properties (2015)
Wessig, Pablo ; Budach, Dennis B. ; Thünemann, Andreas F.
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.
The use of an acoustic levitator to follow crystallization in small droplets by energydispersive X-ray diffraction (2006)
Leiterer, York ; Leitenberger, Wolfram ; Emmerling, Franziska ; Thünemann, Andreas F. ; Panne, Ulrich
Multicompartment micelles formed by self-assembly of linear ABC triblock copolymers in aqueous medium (2005)
Kubowicz, Stephan ; Baussard, Jean-Francois ; Lutz, Jean-Francois ; Thünemann, Andreas F. ; von Berlepsch, Hans ; Laschewsky, André
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