Design of nanostructured siloxane-gelatin coatings: Immobilization strategies and dissolution properties

Owing to the outstanding service life of metallic prostheses, a substantial effort has been put into their surface modification to improve biocompatibility and reduce metallic ion diffusion. To satisfy these requirements, the coating materials obtained using the sol-gel method, with its wide range of tuning properties, have been extensively explored. The well-known biocompatibility of these materials makes them good candidates for different biomedical applications. We designed a series of siloxane-gelatin hybrids to be used as coatings for metallic implants or in controlled delivery systems. Two different matrixes were designed based on methyltrimethoxysilane (MTMOS), tetraethoxysilane (TEOS) and 3-glycidoxypropyltrimethoxysilane (GPTMS) alkoxysilane precursors. In one hybrid coating gelatin was physically entrapped and in the other it was linked to the siloxane network by covalent bonds. Synthesis parameters were established by studying the sol-gel reaction using 29Si nuclear magnetic resonance (29Si NMR), which also allowed quantification of the network connectivity. Dissolution and degradation studies showed the effectiveness of GPTMS as a covalent coupling agent between the silica and gelatin phases; it increased the stability of the coatings in aqueous media. The aim of this study was to design a set of hybrid materials with highly tailorable properties, suitable for their potential biomedical applications.