Enhanced osteogenic differentiation of osteoblasts on CaTiO₃ nanotube film

Improved implant-bone interface interaction for rapid formation of strong and long-lasting bond is significantly important in orthopedic clinics. Herein, Ca-doped TiO₂ nanotube film (M-CaNTs) with enhanced adhesion strength was fabricated on titanium (Ti) surface by an anodization-hydrothermal treatment. Results showed that TiO₂ nanotube film (M-NTs) fabricated by modified anodization was amorphous, exhibiting 100-nm diameter and 12-nm tube wall thickness. After hydrothermal treatment, the nanotubular structure of M-CaNTs kept integrated, but was volume-expanded, exhibiting a decreased diameter (∼ 60 nm) and an increased wall thickness (∼ 30 nm). The formation of M-CaNTs proceeded preferentially at the interior surfaces of the closely aligned nanotubes, involving an in situ dissolution-recrystallization process. Though the adhesion strength of M-CaNTs was weakened by the volume-expansion derived internal stress, it was still higher than that of the traditionally obtained one. In the in vitro investigations, the combination of nanotubular structure and Ca²⁺ could expectedly enhance the attachment, spreading and proliferation of MC3T3-E1 cells, as well as promote the expressions of bone-specific genes, intracellular proteins and ALP activity, which in turn accelerated collagen secretion and ECM mineralization. This work provides an attractive potential for the surface modification of Ti-based implants in clinical application.