Morphologically modified surface with hierarchical micro-/nano-structures for enhanced bioactivity of titanium implants

Surface morphology of titanium (Ti) implants plays an important role in regulating cell behaviors at the interface. The purpose of our study was to investigate the effect of surface structures from microscale to nanoscale on the proliferation and differentiation of precursor osteoblasts. Sandblasting and acid etching and anodic oxidation were used to fabricate the micro-structure and nano-structure on Ti surface. Physical properties including surface topography, roughness and wettability were measured by scanning electron microscopy, laser scanning microscopy and contact angle goniometry, respectively. The bioactivity and cytocompatibility of different surface morphology were investigated in vitro. The results showed that the hierarchical micro-/nano-structured surface composed of micro-valleys and self-assembly nanotubes was successfully constructed on the substrate of Ti. The hydrophilicity of the micro-/nano-structured surface was significantly heightened in comparison with the polished surface, micro-structured surface and nano-structured surface. Moreover, a compact layer of hydroxyapatite was observed on the micro-/nano-structured surface after immersing in simulated body fluid for 14 days. Higher proliferation rate and alkaline phosphatases activity as well as enhanced biomineralization were also verified on the hierarchically structured surface. All results indicated that the integration of multiscale structures of micro-valleys and nanotubes can provide a better surrounding microenvironment to improve cell sensitivities and promote the cell proliferation and differentiation.