Effects of solution pH on the structure and biocompatibility of Mg-containing TiO ₂ layer fabricated on titanium by hydrothermal treatment

Pure titanium was subjected to surface modification in order to improve its bioactivity. Samples wet-polished by abrasive paper were hydrothermally treated in 0.1 mol/l MgCl ₂ solutions with different pH values (5.5, 7.5 and 9.5) at 200°C for 24 h. By forming nano-sized anatase precipitations, hydrothermal treatment increased the thickness of the oxide layer obviously and Mg was found to distribute all through the oxide layer. Treatment in solution with a low pH formed TiOMg bond as MgTiO ₃ , whereas, high pH induced Mg(OH) ₂ precipitation onto the samples. Cell attachment and spreading were improved on samples treated in the solution of pH 5.5. As treatment solution pH rose, protein (Bovine Serum Albumin, BSA) adsorption on treated samples increased; however, initial osteoblast attachment and spreading were impaired. It is suggested that, hydrothermal treatment in MgCl ₂ solution can improve the bioactivity of titanium by immobilizing Mg into oxide layer, however, the chemical state and amount of Mg should be well controlled.