EFFECT OF PH ON PROTEIN ADSORPTION TO HYDROXYAPATITE AND TRICALCIUM PHOSPHATE CERAMICS

Calcium phosphate ceramics used for clinical applications vary conside rably in their phase composition. A range of hydroxyapatite and trical cium phosphate powders, some of which are used in plasma-sprayed coati ngs for metal prostheses, were found to leach substances which change the pH of water and cell culture medium. The adsorption of serum prote ins from cell culture medium to the same hydroxyapatite and tricalcium phosphate ceramics was compared by sodium dodecyl sulphate-polyacryla mide gel electrophoresis and individual bands identified by enhanced c hemiluminescence immunodetection and gas chromatography sequencing. Th e iron transport protein transferrin showed distinct differences in ad sorption to a variety of hydroxyapatite and tricalcium phosphate powde rs, with higher concentrations of transferrin adsorbed to powders whic h caused no change or a drop in the pH of cell culture medium or water . Transferrin was also adsorbed to Biotal HA 120 in greater concentrat ions at a lower pH than it was at a higher pH. These preliminary studi es show that pH changes brought about by the leaching of soluble ions may have an effect on protein adsorption. (C) 1997 Elsevier Science Li mited.