Effect of serum proteins on osteoblast adhesion to surface-modified bioactive glass and hydroxyapatite

Previous studies indicate that modification of the surface of porous bioact ive glass promotes osteoblast function. We hypothesize that bone formation on treated bioactive glass is due to the selective adsorption of serum atta chment proteins. To test this hypothesis, we examined the profile of protei ns adsorbed to treated bioactive glass and compared these proteins with tho se adsorbed to untreated bioactive glass and porous hydroxyapatite. Porous bioactive glass was treated with Tris-buffered electrolyte solution to gene rate a calcium phosphate-rich surface layer and then immersed in tissue-cul ture medium containing 10% serum. Proteins adsorbed to the ceramic surfaces were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blot analysis. Porous hydroxyapatite bound a higher amount of total protein than did the other substrates. However, surface-modified poro us bioactive glass adsorbed more fibronectin than did hydroxyapathe. The ef fect of serum-protein adsorption on osteoblast adhesion to bioactive glass and hydroxyapatite was also evaluated. Cell adhesion to porous bioactive gl ass that was surface-modified and serum-treated was significantly greater t han to porous bioactive glass that was either surface-modified or serum-tre ated. Furthermore, cell adhesion to porous bioactive glass treated to form the dual layer of calcium phosphate and serum protein was significantly hig her than adhesion to porous hydroxyapatite with adsorbed serum protein. Res ults of the study strongly suggest that adsorption of serum fibronectin to the surface of modified porous bioactive glass coated with calcium phosphat e may be responsible for enhanced osteoblast -adhesion.