ADSORPTION PROPERTIES OF ACIDIC AND BASIC PROTEINS ON THE SURFACE OF CARBONATE-CONTAINING HYDROXYAPATITE

概要

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Carbonate-containing hydroxyapatites (HAp's) were prepared at 6.0, 7.0, 8.5, or 10.5 of pH, and the content of carbonate increased as the increase of pH: 0.9 - 6.3 mass%-CO3/g-HAp. Increase of the content made the crystallite size of (001) face smaller by 40 %. IR spectra showed that the increase of carbonate content led to an increase of OH-substituted carbonate species compared to PO4-substitued one. The adsorption properties of two kinds of proteins: acidic bovine serum albumin (BSA) and basic egg white lysozyme (LSZ) were investigated at 295 K on the HAp's of different contents of carbonate. All the adsorption isotherms followed the Langmuir-type adsorption. The saturated-adsorbed amount of BSA decreased with the increase of the content of carbonate. Two reasons were proposed for the decrease of the amount. Firstly, retard of HAp crystal growth along the c-axis gave rise to relatively less amount of the C-site on a-and b-faces: less amount of adsorption site for BSA. Secondly, increase of the OH-substituted carbonate may cause less amount of OH vacancy and to inhibit the carboxyl ion of BSA on the C-site. LSZ, which is considered to be adsorbed on the P site on c-face, had little dependency of the content, suggesting that neither crystallographic change nor composition of two kinds of carbonate species had an effect on LSZ adsorption.
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