ADSORPTION OF PROTEIN ON NONSTOICHIOMETRIC CALCIUM STRONTIUM HYDROXYAPATITE

The adsorption of bovine serum albumin (BSA) on synthesized non-stoich iometric calcium-strontium hydroxyapatite (CaSrHAP) with various Ca-Sr components and textures was investigated. The adsorption isotherms of BSA on CaSrHAP particles were pseudo-langmuir type. The saturated amo unts of adsorbed BSA (n(s)), which are the plateau values of the adsor ption isotherms, linearly increased with the Sr/(Ca+Sr) ratio. Also, n (s) values increased with increasing (Ca+Sr)/P molar ratio, suggesting that the electrostatic attractive force between BSA and CaSrHAP parti cles is a determining factor of n(s). Despite their large cation/P rat io, however, two particles exhibiting agglomerates with uneven surface s gave small n(s) values. This fact could be explained by the differen ce in the particle texture between these two particles and the others; large acicular particles with flat surfaces are advantageous for the adsorption of negatively charged BSA because of the large number of po sitively charged adsorption sites on the exposed ac or be crystal plan es. It was suggested therefore that the texture of the particle is sig nificant in the adsorption of BSA.