Effect of solvent composition on the bioactive coating fabricated by micro-arc oxidation combined with electrophoretic deposition

In this work, to improve the bioactivity of titanium (Ti) used as an implant material, an in situ composite coating of hydroxyapatite/titanium dioxide (HA/TiO₂) was prepared on the surface of a Ti substrate using electrophoretic deposition combined with a micro-arc oxidation (EPD–MAO) technique in a 0.2M NaOH electrolytic solution with various ethanol concentrations (0, 25 and 50 vol.-%). The addition of ethanol to the electrolytic solution inhibited gaseous emission at the electrode generated by the electrolysis of water and allowed for efficient incorporation of HA particles into the coating layer. The surface morphology, roughness and chemical composition of the coating layer were affected by the ethanol concentration. The corrosion resistance of the sample was examined by potentiodynamic polarisation measurements. The treated sample showed a low corrosion rate compared with an untreated Ti sample. The presence of an apatite-like phase on the treated sample surface after 5 days of soaking in a simulated body fluid (SBF) demonstrates a high bioactivity potential. The cell proliferation assay and alkaline phosphatase (ALP) ability test were used to evaluate osteoblast cell behaviour. The coating layer formed with an electrolytic solution containing 25 vol.-% ethanol showed the greatest cell ability.