A unique hybrid-structured surface produced by rapid electrochemical anodization enhances bio-corrosion resistance and bone cell responses of β-type Ti-24Nb-4Zr-8Sn alloy

Ti-24Nb-4Zr-8Sn (Ti2448), a new β-type Ti alloy, consists of nontoxic elements and exhibits a low uniaxial tensile elastic modulus of approximately 45 GPa for biomedical implant applications. Nevertheless, the bio-corrosion resistance and biocompatibility of Ti2448 alloys must be improved for long-term clinical use. In this study, a rapid electrochemical anodization treatment was used on Ti2448 alloys to enhance the bio-corrosion resistance and bone cell responses by altering the surface characteristics. The proposed anodization process produces a unique hybrid oxide layer (thickness 50–120 nm) comprising a mesoporous outer section and a dense inner section. Experiment results show that the dense inner section enhances the bio-corrosion resistance. Moreover, the mesoporous surface topography, which is on a similar scale as various biological species, improves the wettability, protein adsorption, focal adhesion complex formation and bone cell differentiation. Outside-in signals can be triggered through the interaction of integrins with the mesoporous topography to form the focal adhesion complex and to further induce osteogenic differentiation pathway. These results demonstrate that the proposed electrochemical anodization process for Ti2448 alloys with a low uniaxial tensile elastic modulus has the potential for biomedical implant applications.