FORMATION OF HYDROXYAPATITE IN THE PRESENCE OF BOVINE SERUM ALBUMIN IN AN AQUEOUS PHASE

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Bovine serum albumin(BSA) retarded the transformation to hydroxyapatite(HAP) from amorphous calcium phosphate(ACP) which was formed immediately after mixing CaCl₂ wit K₂HPO₄ in an aqueous phase. It was experimentally confirmed that the higher the concentration of BSA, the more the uptake of phosphate ion(Pi) from a mother solution was delayed. The mechanism for the retardation was as follows: The crystal nucleus and/or embryo of HAP adsorbs BSA. It could inhibit Pi from getting to the active site for the crystal growth of HAP due mainly to electrostatic and steric repulsion, because the solution pH was higher than that of isoelectric point for BSA(i.e.p.= pH 4.8-5.3) and, therefore, Pi and BSA are repulsive each other. The retardation effect was more remarkable in the presence than in the absence of phosphorylated cellulose(Phos. Cell).