Bioactivity evaluation of porous TiO2 surface formed on titanium in mixed electrolyte by spark anodization

In this study, the bioactivity of porous TiO2 surfaces formed on titanium in mixed electrolyte by spark anodization was investigated both in vitro and in vivo. To fabricate geometric micropores on titanium for implant applications, plasma electrolytic oxidation (PEO) was carried out in an electrolyte consisting of 1.5M H2SO4+0.7M H3PO4+0.4M H2O2. The surface characteristics of the microporous Ti layer were investigated by FE-SEM, EDS, and XPS, and the bioactivity of PEO surfaces was assessed by MC3T3-E1 cell culture, cell viability, ALP activity, and in vivo immune response. A gradual increase of the spark width and the voltage applied caused pitting that leads to the formation of circular pores distributed over the entire surface. The fraction of the surface area occupied by pores increased as the anodizing time increased. The microporous TiO2 surface provided higher cell adhesion, proliferation and viability compared to the metallic titanium control group. Cells cultured on the surface of geometrical microporosity demonstrated higher ALP activity. Hypodermic tissue and connective tissue were well attached on anodized surface after 10 and 20min. In particular, on the micropore-formed surface after 30min, an abundant amount of hypodermic and connective tissue was observed among the adjacent micropores. •In this study, the in vitro and in vivo bioactivity of anodized TiO2 layers was assessed.•The fraction of occupied micropores on the titanium surface increased with the anodizing time.•The anodic TiO2 micropore layer provided higher cell adhesion, proliferation, and viability.•Hypodermic tissue and connective tissue were well attached on the anodized surface.