Surface engineering of stainless steel materials by covalent collagen immobilization to improve implant biocompatibility

Abstract

It was shown recently that the deposition of thin films of tantalum and tantalum oxide enhanced the long-term biocompatibility of stainless steel biomaterials due to an increase in their corrosion resistance. In this study, the authors used this tantalum oxide coating as a basis for covalent immobilization of a collagen layer, which should result in a further improvement of implant tissue integration. Because of the high degrdn. rate of natural collagen in vivo, covalent immobilization as well as carbodiimide induced crosslinking of the protein was performed. It was found that the combination of the silane-coupling agent aminopropyl triethoxysilane and the linker mol. N,N'-disulfosuccinimidyl suberate was a very effective system for collagen immobilizing. Mech. and enzymic stability testing revealed a higher stability of covalent bound collagen layers compared to phys. adsorbed collagen layers. The biol. response induced by the surface modifications was evaluated by in vitro cell culture with human mesenchymal stem cells as well as by in vivo s.c. implantation into nude mice. The presence of collagen clearly improved the cytocompatibility of the stainless steel implants which, nevertheless, significantly depended on the crosslinking degree of the collagen layer.