Sol-gel-derived TiO2-SiO2 implant coatings for direct tissue attachment.: Part I:: design, preparation and characterization

A series of sol-gel derived TiO2-SiO2 mixed oxide coatings were prepared by carefully controlling the process parameters to obtain silica-releasing coatings consisting of nanoparticles. These features are of paramount importance for enhanced cell adhesion and activation. To achieve both these goals the Ti-alkoxide and Si-alkoxide were first separately hydrolysed and the titania silica mixed sol was further reacted before the dipping process to obtain the desired particle sizes resulting to the biologically favourable topographical features. Silica release was observed from all the prepared coatings and it was dependent on SiO2 amount added to the sols, i. e., the higher the added amount the higher the release. In addition, calcium phosphate was able to nucleate on the coatings. From the obtained SiO2 dissolution data, together with the detailed XPS peak analysis, the mixed oxide coatings are concluded to be chemically heterogeneous, consisting of TiO2 and SiO2 species most likely linked together by Ti-O-Si bonds. TiO2 is chemically stable making long-term implant coating possible and the desired nanoscale dimensions were well preserved although the composition was changed as a consequence of SiO2 dissolution under in vitro conditions.