Electrically bioactive coating on Ti with bi-layered SnO₂-TiO₂ hetero-structure for improving osteointegration

The potential for the use of electric stimulation to control cell behavior on a surface has been well documented. In terms of orthopaedic applications, there is a need to develop bioactive surfaces with a built-in electric field for clinically relevant materials, such as load-bearing titanium (Ti). In this work, a bi-layered SnO₂-TiO₂ coating is fabricated via microarc oxidation and subsequent hydrothermal treatment to adjust the surface electrical properties for improving bioactivity. An oxidized titanium interlayer on Ti substrate allows the growth of SnO₂ nanorods with different morphologies, which leads to a built-in n-n heterojunction of SnO₂ and TiO₂ on the Ti surface with varied surface electrical properties. The crystallization of the TiO₂ interlayer facilitates the growth of SnO₂ nanorods, showing excellent hydrophilicity and good apatite-inducing ability due to the formation of a heterojunction. The results suggest that the bi-layered SnO₂-TiO₂ coating with electrically stimulated bioactivity could provide a novel way to enhance osteointegration on the Ti surface.