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.