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Cells and Materials

Abstract

Octacalcium phosphate (OCP) has been advocated to be a precursor of biomineral s. Tn this report , we aimed at investigating OCP hydrolysis and the interaction of OCP and its hydrolyzates (apatitic products) with bovine serum albumin (BSA). A batch of synthetic OCP was allowed to hydrolyze either (a) in deionized water at 70°C or (b) in Tris buffer (pH 7.4) containing 2 ppm fluoride at 37°C. OCP hydrolysis was completed within reasonable experimental periods: after 48 hours at 70°C and after 10 days at 37°C in the presence of fluoride. The adsorption isotherms of BSA onto the original OCP and its various hydrolyzates were determined at pH 7.4 and 37 °C. The BSA adsorption onto all the adsorbents was described by a Langmurian model. Remarkable findings were that: (1) when the maximum number of BSA adsorption sites was expressed on basis of unit surface area (N , mols/m2), the greatest values of N was obtained for the original OCP; (2) the N values became smaller with the advance of OCP-apatite conversion in both hydrolysis systems; (3) the affinity values (K, ml/µmol) were relatively constant for the OCP anti the non-fluoridated hydrolyzates, while the K values increased markedly after hydrolysis of OCP in the presence of fluoride. The results of the present work support the hypothesis that the process of precursor precipitation and its subsequent hydrolysis taking place in forming hard tissues may be modulated through the matrix protein-crystals interaction. It seems likely that fluoride ions has a dual role, i.e., acceleration of OCP hydrolysis and, once incorporated into the crystals, enhancement of the protein-mineral interaction.

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