Early osteoblast-like cell spreading on hydrophilic phosphate ion-incorporated titanium oxide surface

Recent studies have demonstrated the potential advantages of titanium(Ti) oxide layer with possibly bioactive surface composition in improving implant osseointegration. Phosphate ion is a major component of bioactive hydroxyapatite, but few studies have reported its osteoconductive properties. This study investigated the surface characteristics of a crystalline phosphate ion-incorporated Ti oxide(P-Ti) surface produced by hydrothermal treatment for future biomedical application. We evaluated osteoblast-like cell(MC3T3-E1) spreading and compared them with those of relatively smooth machined or micro-rough grit-blasted/etched surfaces. The surface characteristics were investigated by scanning electron microscopy(SEM), thin-film X-ray diffractometry, X-ray photoelectron spectroscopy, contact angle measurement, and stylus profilometry. The morphologies of spread cells on different surfaces were evaluated by SEM observation. Hydrothermal treatment with H ₃PO₄ produced a crystalline phosphate ion-incorporated oxide(Ti₂O(PO₄)₂(H₂O)₂) surface approximately 5 μm in thickness, which had needlelike surface microstructures, intermediate microroughness, and superior wettability compared with control surfaces. After immersion in Hank's balanced salt solution, P-Ti surfaces showed considerable amount of apatite formation on their surfaces indicating their in vitro bioactivity. P-Ti surfaces promoted cell spreading, they showed the highest proportion of fully spread cells among investigated surfaces after 1 h of incubation. These results indicate in vitro osteoconductive properties of P-Ti surface.