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Reutlingen, Germany

Steuer H.,NMI Technology Transfer GmbH | Krastev R.,University of Tubingen | Lembert N.,NMI Technology Transfer GmbH
Journal of Biomedical Materials Research - Part B Applied Biomaterials | Year: 2014

Positively charged metallic oxides prevent blood coagulation whereas negatively charged metallic oxides are thrombogenic. This study was performed to examine whether this effect extends to metallic oxide nanoparticles. Oscillation shear rheometry was used to study the effect of zinc oxide and silicon dioxide nanoparticles on thrombus formation in human whole blood. Our data show that oscillation shear rheometry is a sensitive and robust technique to analyze thrombogenicity induced by nanoparticles. Blood without previous contact with nanoparticles had a clotting time (CT) of 16.7 ± 1.0 min reaching a maximal clot strength (CS) of 16 ± 14 Pa (G') after 30 min. ZnO nanoparticles (diameter 70 nm, +37 mV zeta-potential) at a concentration of 1 mg/mL prolonged CT to 20.8 ± 3.6 min and provoked a weak clot (CS 1.5 ± 1.0 Pa). However, at a lower concentration of 100 μg/mL the ZnO particles dramatically reduced CT to 6.0 ± 0.5 min and increased CS to 171 ± 63 Pa. This procoagulant effect decreased at lower concentrations reaching the detection limit at 10 ng/mL. SiO2 nanoparticles (diameter 232 nm, -28 mV zeta-potential) at high concentrations (1 mg/mL) reduced CT (2.1 ± 0.2 min) and stimulated CS (249 ± 59 Pa). Similar to ZnO particles, this procoagulant effect reached a detection limit at 10 ng/mL. Nanoparticles in high concentrations reproduce the surface charge effects on blood coagulation previously observed with large particles or solid metal oxides. However, nanoparticles with different surface charges equally well stimulate coagulation at lower concentrations. This stimulation may be an effect which is not directly related to the surface charge. © 2013 Wiley Periodicals, Inc.

Girndt M.,Martin Luther University of Halle Wittenberg | Fiedler R.,Martin Luther University of Halle Wittenberg | Martus P.,University of Tubingen | Pawlak M.,NMI Technology Transfer GmbH | And 11 more authors.
European Journal of Clinical Investigation | Year: 2015

Background: Haemodialysis patients suffer from chronic systemic inflammation and high incidence of cardiovascular disease. One cause for this may be the failure of diseased kidneys to eliminate immune mediators. Current haemodialysis treatment achieves insufficient elimination of proteins in the molecular weight range 15-45 kD. Thus, high cut-off dialysis might improve the inflammatory state. Design: In this randomized crossover trial, 43 haemodialysis patients were treated for 3 weeks with high cut-off or high-flux dialysis. Inflammatory plasma mediators, monocyte subpopulation distribution and leucocyte gene expression were quantified. Results: High cut-off dialysis supplemented by a low-flux filter did not influence the primary end-point, expression density of CD162 on monocytes. Nevertheless, treatment reduced multiple immune mediators in plasma. Such reduction proved - at least for some markers - to be a sustained effect over the interdialytic interval. Thus, for example, soluble TNF-receptor 1 concentration predialysis was reduced from median 13·3 (IQR 8·9-17·2) to 9·7 (IQR 7·5-13·2) ng/mL with high cut-off while remaining constant with high-flux treatment. The expression profile of multiple proinflammatory genes in leucocytes was significantly dampened. Treatment was well tolerated although albumin losses in high cut-off dialysis would be prohibitive against long-term use. Conclusions: The study shows for the first time that a dampening effect of high cut-off dialysis on systemic inflammation is achievable. Earlier studies had failed due to short study duration or insufficient dialysis efficacy. Removal of soluble mediators from the circulation influences cellular activation levels in leucocytes. Continued development of less albumin leaky membranes with similar cytokine elimination is justified. © 2015 Stichting European Society for Clinical Investigation Journal Foundation.

Beissner M.,Max Planck Institute for Brain Research | Dutertre S.,University of Queensland | Schemm R.,Max Planck Institute for Biophysical Chemistry | Danker T.,NMI Technology Transfer GmbH | And 4 more authors.
Molecular Pharmacology | Year: 2012

α-Conotoxins are subtype-selective nicotinic acetylcholine receptor (nAChR) antagonists. Although potent α3β2 nAChR-selective α-conotoxins have been identified, currently characterized α-conotoxins show no or only weak affinity for α4β2 nAChRs, which are, besides α7 receptors, the most abundant nAChRs in the mammalian brain. To identify the determinants responsible for this difference, we substituted selected amino acid residues in the ligand-binding domain of the α4 subunit by the corresponding residues in the α3 subunit. Two-electrode voltage clamp analysis of these mutants revealed increased affinity of α-conotoxins MII, TxIA, and [A10L]TxIA at the α4(R185I)β2 receptor. Conversely, α-conotoxin potency was reduced at the reverse α3(I186R)β2 mutant. Replacement of α4Arg185 by alanine, glutamate, and lysine demonstrated that a positive charge in this position prevents α-conotoxin binding. Combination of the R185I mutation with a P195Q mutation outside the binding site but in loop C completely transferred high α-conotoxin potency to the α4β2 receptor. Molecular dynamics simulations of homology models with docked α-conotoxin indicate that these residues control access to the α-conotoxin binding site. Copyright © 2012 The American Society for Pharmacology and Experimental Therapeutics.

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