Ca substitution of Sr in Sr-doped TiO2 nanotube film on Ti surface for enhanced osteogenic activity

Abstract The intrinsic bioinertness of titanium (Ti) as an endosseous implant is still a grand challenge to achieve faster and stable implant osseointegration. A multitude of TiO2 nanotubes loaded with Sr have been developed to improve the biological performance of Ti implants, which, however, remained limited. In this study, a Sr&Ca co-doped TiO2 nanotube film (M-SrCaNT) was fabricated using a modified anodization, following by hydrothermal treatment. Results showed that half amount of Sr in Sr-doped TiO2 nanotubes (M-SrNT) could be substituted by Ca to generate M-SrCaNT, without changing the nanotubular structure. Interestingly, M-SrNT and M-SrCaNT revealed similar micro/nano-topographic surface characteristics. The production of osteogenic signals by TiO2 nanotubes (M-NT) was obviously limited as compared with Ti, which could be could be compensated by M-SrNT with superior surface micro/nano-topography and bioactive element Sr. Furthermore, as compared with M-SrNT, M-SrCaNT with the co-presence of Sr&Ca exhibited much more efficient in enhancing the attachment, proliferation and osteogenic activities (gene expressions, extracellular matrix synthesis and mineralization) of MC3T3-E1 cells. This study provided an outstanding biomimetic surface constructed by co-incorporating Sr&Ca into TiO2 nanotubular structure on Ti implant. It represented a promising approach for rapid formation of strong and long-lasting bond between implant-bone interface.