Abstract
INTRODUCTION: Despite great progress made in developing orthopedic implants, the development of titanium (Ti) implants with ideal early osseointegration remains a big challenge. Our pilot study has demonstrated that Si-TiO(2) nanotubes on the surface of Ti substrates could enhance their osteogenic activity. Hence, in this study, we aim to comprehensively evaluate the effects of silicon-doped titania (Si-TiO(2)) nanotubes on the osseointegration property of Ti implants. MATERIALS AND METHODS: The Ti implants were surface modified with Si-TiO(2) nanotubes through in situ anodization and Si plasma immersion ion implantation (PIII) method. Three groups were divided as Ti implants (Ti), Ti modified with TiO(2) nanotubes (TiO(2)-NTs) and Ti modified with Si-TiO(2) nanotubes (Si-TiO(2)-NTs). The morphology of Si-TiO(2) nanotubes was observed by scanning electron microscope. The growth and osteogenic differentiation of MC3T3-E1 cells on the Ti implants were evaluated. Further, the pull-out tests and in vivo osseointegration ability evaluation were performed after implanting the screws in the femur of Sprague Dawley rats. RESULTS: The Si-TiO(2) nanotubes could be seen on the surface of Ti implants. The MC3T3-E1 cells could grow on the surface of Ti, TiO(2)-NTs and Si-TiO(2)-NTs, and showed fast proliferation rate on the Si-TiO(2)-NTs. Moreover, the production of some osteogenesis-related proteins (ALP and Runx2) at one week and calcium deposition at four week was also enhanced in Si-TiO(2)-NTs rather than other groups. In vivo osseointegration results showed that Si-TiO(2) nanotube-modified Ti screws had higher pullout force at two and four weeks as well as enhanced new bone formation at six weeks compared to bare Ti screws and Ti screws modified with TiO(2) nanotubes alone. DISCUSSION: The modification of Si-TiO(2)-NTs on the Ti substrate could generate a nanostructured and hydrophilic surface, which can promote cell growth. Moreover, the existence of the TiO(2) nanotubes and Si element also can improve the in vitro osteogenic differentiation of MC3T3-E1 cells and early bone formation around the implanted screws. Together, findings from this study show that surface modification of Ti implants with Si-TiO(2) nanotubes could enhance early osseointegration and therefore has the potential for clinical applications.