Enhanced osteogenic activity of anatase TiO2 film: Surface hydroxyl groups induce conformational changes in fibronectin

•Anatase and rutile films with similar topography and hydrophilicity were obtained.•Anatase films promoted osteoblast adhesion, differentiation and mineralization.•A mechanism for the enhanced osteogenic activity of anatase films is proposed.

In this study, with an attempt to identify the effects of TiO2 crystalline phase compositions on the osteogenic properties, the anatase and rutile TiO2 thin films with similar film thickness, surface topography and hydrophilicity were prepared on Si (100) substrates by atomic layer deposition (ALD), subsequent thermal annealing and ultraviolet irradiation. The films were studied with XRD, XPS, FE-SEM, AFM, FTIR and contact angle measurements. In vitro cellular assays showed that the anatase phase led to better osteoblast compatibility in terms of adhesion, proliferation, differentiation, mineralization as well as osteogenesis-related gene expression when compared with the rutile phase. We investigated the difference between the anatase and rutile TiO2 films at the biomolecular level to explain the enhanced osteogenic activity of the anatase film. It was found that the presence of more TiOH groups on anatase surface induced more cell-binding sites of fibronectin (FN) exposed on its surface, causing a more active conformation of the adsorbed FN for subsequent osteoblast behaviors.