Induction of octacalcium phosphate by surface modification of TiO2 film prepared by electron cyclotron resonance plasma oxidation

TiO2 (titania) films on titanium substrates were fabricated by electron cyclotron resonance (ECR) plasma oxidation. A calcification experiment of the Ti substrates treated with the ECR plasma was carried out by immersing in a supersaturated solution with respect to hydroxyapatite (HA) and octacalcium phosphate (OCP), but slightly saturated with respect to dicalcium phosphate, dihydrate (DCPD). After the immersion, OCP precipitated predominantly on TiO2 film, whereas formation of HA, the most stable phase under physiological condition, was inhibited. The calcification ability was affected by the substrate temperature during the ECR plasma oxidation. The surface roughness increased with increasing the oxidation temperature. These results indicate that the surface oxidation by ECR plasma modulates the surface characteristics to enhance OCP precipitation.