Hydrophilic/electron-acceptor surface properties of metallic biomaterials and their effect on osteoblast cell activity

Mice osteoblast cells were cultured on samples of 316L stainless steel and titanium alloy (Ti-6Al-4V) with different surface treatments. The resulting cell differentiation was correlated with the solid surface tension and electron-acceptor surface tension parameter of the biomaterial samples. Both of these characteristics were determined through contact angle measurements, using the Lifshitz-van der Waals/Lewis acid-base interaction model. Before calculating the surface tension of the biomaterials, the experimental contact angles were corrected for the effect of roughness using the Wenzel equation. For this calculation, the roughness characteristics of the solid surfaces were determined using atomic force microscopy and interferometric profilometry at the nano-scale and micro-scale, respectively. It was found that osteoblast cell differentiation directly related to the implant surface tension and electron-acceptor properties. The alkaline phosphatase activity increased both with increasing surface tension and increasing electron-acceptor surface tension parameter of the implant materials. These results suggest that the formation of surface hydroxyl groups with acidic character gives rise to enhanced attachment of osteoblast cells.