Role of adsorbed proteins on hydroxyapatite-coated titanium in osteoblast adhesion and osteogenic differentiation

The method of plasma-spray coating of hydroxyapatite (HA) onto pure titanium has been demonstrated to be effective to enhance the osteogenic differentiation and accelerate bone regeneration. Yet it is still a big challenge to figure out the interplay among implant surface properties, adsorbed proteins and cell-surface interactions. In this study, the plasma-sprayed HA-coated titanium (HA-Ti) surface was compared with the titanium substrate in terms of protein adsorption, cell adhesion and differentiation. The phase composition, wettability and topography were characterized. Compared to the Ti substrate, the HA-Ti had a smaller water contact angle, but larger micro-scale roughness, and showed a poorer ability to adsorb fibronectin (Fn), bovine serum albumin (BSA) and serum proteins. However, it could adsorb larger amount of recombinant human bone morphogenetic protein 2 (BMP-2). The osteoblasts and bone marrow mesenchymal stem cells (BMSCs) tended to adhere on the Ti substrate. By contrast, the BMSCs cultured on the HA-Ti showed a stronger tendency toward osteogenesis differentiation.