HEMOCOMPATIBILITY OPTIMIZATION OF IMPLANTS BY HYBRID STRUCTURING

State of the art in biomaterial research and implant design is a compr omise between functionality and biocompatibility. Consequently, result s often have disadvantages with respect to both aspects. With regard t o biocompatibility, the activation of the clotting system by alloplast ic materials is of great significance, because it necessitates anticoa gulant therapy. Further improvements in implant technology require an understanding of the interactions between blood and implants. Therefor e a microscopic model of thrombogenesis at alloplastic surfaces is bri efly presented, relating thrombogenicity of a material to the electron ic structure of its surface. The electronic requirements for high haem ocompatibility, which result from this model (especially a low band-ga p density of states and a high surface conductivity) are fulfilled by an amorphous alloy of silicon and carbon (a-SiC:H). The advantage of a morphous materials is that they do not obey stoichiometric rules. Thus they allow a continuous adjustment of the electronic parameters witho ut fundamental changes in their mechanical and chemical properties. Th e theoretical results were checked in vitro by total internal reflecti on intrinsic fluorescence (TIRIF) spectroscopy as well as thrombelasto graphy experiments (TEG). In comparison with conventional materials su ch as titanium or LTI carbon, the TEG-clotting time of a-SiC:H-coating s was prolonged by in excess of 200 per cent. As a consequence, a-SiC: H is well suited as a haemocompatible coating material for hybrid stru cturing of cardiovascular implants.