Titanium alloy surface oxide modulates the conformation of adsorbed fibronectin to enhance its binding to α5β1 integrins in osteoblasts

Rapuano BE, Lee JJE, MacDonald DE. Titanium alloy surface oxide modulates the conformation of adsorbed fibronectin to enhance its binding to a5 beta 1 integrins in osteoblasts. ?Eur J Oral Sci 2012; 120: 185194. (C) 2012 Eur J Oral Sci Our laboratory has previously demonstrated that heat (600 degrees C) or radiofrequency plasma glow discharge (RFGD) pretreatment of a titanium alloy (Ti6Al4V) increased the net negative charge of the alloy's surface oxide and the attachment of osteoblastic cells to adsorbed fibronectin. The purpose of the current study was to investigate the biological mechanism by which these surface pretreatments enhance the capacity of fibronectin to stimulate osteoblastic cell attachment. Each pretreatment was found to increase the binding (measured by ELISA) of a monoclonal anti-fibronectin Ig to the central integrin-binding domain of adsorbed fibronectin, and to increase the antibody's inhibition of osteogenic cell attachment (measured by hexosaminidase assay). Pretreatments also increased the binding (measured by ELISA) of anti-integrin IgGs to the a5 and beta 1 integrin subunits that became attached to fibronectin during cell incubation. These findings suggest that negatively charged surface oxides of Ti6Al4V cause conformational changes in fibronectin that increase the availability of its integrin-binding domain to a5 beta 1 integrins.