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  • Author: HERMANN PETERS x
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Abstract

Drug delivery systems (DDS) ensure that therapeutically effective drug concentrations are delivered locally to the target site. For that reason, it is common to coat implants with a degradable polymer which contains drugs. However, the use of polymers as a drug carrier has been associated with adverse side effects. For that reason, several technologies have been developed to design polymer-free DDS. In literature it has been shown that micro-sized reservoirs can be applied as drug reservoirs. Inkjet techniques are capable of depositing drugs into these reservoirs. In this study, two different geometries of micro-sized reservoirs have been laden with a drug (ASA) using a drop-on-demand inkjet printhead. Correlations between the characteristics of the drug solution, the operating parameters of the printhead and the geometric parameters of the reservoir are shown. It is indicated that wettability of the surface play a key role for drug deposition into micro-sized reservoirs.

Abstract

Reaction of tri-tert-butyl(dihalomethyl)silanes (halo = chloro, bromo) with organolithium compounds, by lithium/halogen or lithium/hydrogen exchange, leads to the corresponding carbenoids which by lithium halide elimination could give the carbenes (t-C4H9)3SiCX. Further intermolecular or intramolecular reaction of these reactive intermediates provides a variety of crowded molecules including alkyltri-tert-butylsilanes, 1,2-bis(tri-tert-butylsilyl)- substituted ethanes and ethenes and ring substituted 1,2-di-tert-butyl-1-silacyclo-butanes. An X-ray structure determination of (E)-1,2-bis(tri-tert-butylsilyl)-1,2-dichloroethene reveals neither a twisting nor an elongation of the CC double bond, but the C = C-Si bond angles exhibit rather unusual values (up to 137.7°) and the Si-C (sp2) bonds are as long as 195 pm.

Tri-tert-butylisopropylsilane was prepared by a two step procedure and characterized by its variable temperature NMR spectra. The attempted synthesis of tetra-tert-butylsilane by reactions of the compound with bromine followed by treatment with methyllithium afforded only tri-tert-butylisopropenylsilane.

Abstract

Endoprostheses such as hip replacements are subject to wear. Lubrication of the joint interface plays a key role in the wear process, but the mechanisms of lubrication is challenging to understand. The main issue is the three-body abrasion which leads to a shorter life cycle. In order to improve the life cycle, the surfaces of the articulating components can be modified, for example by pulsed femtosecond-laser microstructuring. By microstructuring of the implant surface, the viscosity of the synovial fluid between the joint can be increased due to the non-Newtonian properties of the synovia. This leads to better lubrication and therefore lower particle abrasion. The objective of this study was to evaluate the impact of different microstructures on the viscosity of a joint fluid substitute. Various microstructures were investigated in a modified rheometer setup featuring a decreased gap size. As a test fluid, a synovial fluid substitute was used. The results show that an increase in the viscosity of the synovial fluid substitute can be achieved by microstructuring. An increase of viscosity of up to 20 % compared to the unstructured reference was observed with ring-structures with a diameter of 100 μm and a depth of 20 μm.