Impacts of the surface charge property on protein adsorption on hydroxyapatite

Knowledge of the adsorption mechanism of biological molecules on hydroxyapatite (HAP) is essential to the application of HAP chromatography and to the development of HAP-based biomedical materials. Centered on the surface charge of HAP and its impacts on adsorption of proteins, the present study started with the characterization of delta-potential of HAP as a function of the chemical properties of solution in terms of concentration of ions of different types, ionic strength and pH. Then the adsorption of bovine serum albumin (BSA) on HAP was carried out at the same conditions to elucidate the effects of delta-potential on BSA adsorption and the replacement of BSA with PO43- in acidic buffer. A Langmuir isotherm was obtained, indicating a single layer adsorption of BSA on HAP. Finally, the apparent activation energy and the adsorption heat were interpreted from the adsorption at different temperatures. The low magnitude of both the apparent activation energy and the adsorption heat indicated that the fast adsorption of BSA on HAP was a physical adsorption process. (C) 2002 Elsevier Science B.V. All rights reserved.