Modifizierung von Glas- und Titanoberflächen zur Verbesserung der Biokompatibilität
The goal of this study was the improvement of the biocompatibility of glass and titanium by surface modification. In biomaterial science glass is applied, for example, in biomedical sensors or optical waveguides. The functionality of these medical devices may be reduced by unspecific protein adsorption and uncontrolled cell adhesion. For this reason, the interaction of glass surfaces with biological fluids and tissue should be minimised. Titanium is often used for long term implants in orthopaedy or odontology. For these applications a strong interaction of the biomaterial surface with the surrounding tissue is necessary. Hence, the modification of the titanium surface aimed at the formation of a strong interfacial bond between implant and bone tissue. In the first part of this work the minimisation of protein adsorption and cell adhesion on glass surfaces was achieved by immobilisation of methoxylated poly(ethylene glycol) (M-PEG) and carboxymethylated dextran (CMD). These hydrophilic polymers were coupled onto glass surfaces, which were functionalised by silanisation with 3-aminopropyltriethoxysilane (APTES) and by dipcoating with poly(ethylene imine) (PEI) respectively. Furthermore a silane coupling agent (M-PEG-Silane) was prepared, which contains the M-PEG chain und facilitates a single step reaction. The protein resistant properties of the modified glass surfaces were investigated by adsorption of radiolabelled proteins, enzyme linked immunosorbent assay (ELISA) and matrix assisted laser desorption/ionisation time of flight mass spectrometry (MALDI-TOF-MS). Immobilisation of M-PEG and CMD significantly reduced protein adsorption, compared to unmodified glass surfaces. The strongest protein resistant surfaces were those modified with PEI/M-PEG and M-PEG-Silane respectively. Coupling of the hydrophilic polymers also resulted in a strong reduction of cell adhesion. According to the results of the protein adsorption studies surfaces modified with PEI/M-PEG and M-PEG-Silane showed the smallest number of adherent platelets and fibroblasts. In the second part of this work samples made of the titanium alloy Ti-6Al-4V, which is widely used in orthopaedic and odontological applications, were equipped with bioactive substances to improve the adhesion of bone cells and to stimulate of their proliferation. As bioactive molecules, the cell adhesion mediator fibronectin, the pentapeptide GRGDS and the growth factor bone morphogenetic protein 2 (BMP-2) were immobilised onto the titanium surface. For the covalent attachment of these agents the titanium surface was provided with amino groups. On the one hand aminofunctional polymer films of poly(para-xylylene) were deposited on the titanium surface by chemical vapour deposition polymerisation of aminosubstituted [2.2]-para-cyclophanes. On the other hand the metal alloy was silanated with APTES. The amounts of immobilised fibronectin and RGD-peptide were determined by radiolabelling. The biological activity of fibronectin was analysed by ELISA. The covalent bond between the growth factor BMP-2 and the modified titanium surface was proved by means of MALDI-TOF-MS. The short term biological response was evaluated by in vitro biocompatibility tests with primary osteoblasts. None of the investigated titanium surfaces exhibited a toxic effect on the bone cells. Osteoblasts spread very well on titanium surfaces modified with fibronectin, GRGDS and BMP-2, whereas cell spreading on unmodified and aminofunctional titanium was low. All investigated titanium surfaces showed increased bone cell proliferation compared with the unmodified titanium.
info:eu-repo/classification/ddc/540, Chemie, Biokompatibilität, Glas, Titan, Oberflächenmodifizierung
Networked Digital Library of Theses and Dissertations
Publikationsserver der RWTH Aachen University