Crystal Growth and Dissolution of Hydroxyapatite: The Role of Ascorbic Acid

Ascorbic Acid (AA) a very important biomolecule present in relatively high concentrations in blood and other biological fluids, has been rarely investigated with reference to its effect on the biological mineralization-demineralization processes. To our knowledge the pre-sent work is one of extremely limited found in the literature, in which the effect of the presence of AA in mineralizing or demineralizing electrolyte solutions is addressed in a quantitative way. We have used the constant saturation method for the accurate meas-urement of the rates of crystal growth of hydroxyapatite (HAP, Ca5(PO4)3OH) the model compound of the inorganic component of the hard tissues of higher mammals. It was found that both crystal growth and dissolution were accelerated by 4 times (400% of the rates) in the presence of 0.1mM of AA, pH 7.40, 37C, 0.15M NaCl. It was concluded from the detailed characterization of the solid, that the acceleration effect was due to the uptake of AA on the HAP surface.