Ultraviolet-assisted biomimetic coating of bone-like apatite on anodised titanium for biomedical applications

Photocatalytic TiO2 layers were deposited by anodic oxidation on high purity titanium substrates followed by ultraviolet light A (UVA) irradiation in solutions of varying pH (1, 4, 7, and 11) for 12 h. Afterwards, the UVA-treated anodised titanium foils were soaked in simulated body fluid (SBF) for 7 days. The morphological, mineralogical, surface wettability, and in vitro synthesis of the anodised samples were determined. The work showed that the surface morphology and crystallinity of the anodised coating was unchanged after UVA treatment in solutions of varying pH. However, the water contact angle decreased remarkably after UVA treatment, with the sample irradiated in a solution of pH 1 showing the lowest angle (31.8 degrees). After soaking in SBF and with UVA irradiation for 7 days, highly crystallised bone-like apatite layer fully covered the surfaces of the anodised samples. Cross-sectional images revealed that the optimal condition for UVA treatment was at pH 1 (acidic) since it resulted in the thickest layer (2.8 mu m) of bone-like apatite formation after soaking in SBF. The results clearly showed that UVA irradiation assisted the growth of bone-like apatite layer on anodised surfaces.