THE INFLUENCE OF ANIONIC CHITIN DERIVATIVES ON CALCIUM-PHOSPHATE CRYSTALLIZATION

The influence of two water-soluble anionic chitin derivatives. sodium carboxymethyl-chitin (CM-chitin) and phosphoryl-chitin (P-chitin) on t he crystallization of calcium phosphate by seeded growth and turbidime try were studied. The adsorption of these derivatives onto hydroxyapat ite obtained at 37 degrees C, fitted the Langmuir isotherm, The affini ty constant and number of adsorption sites were measured at 2.9 and 1. 69 mu mol m(-2) for CM-chitin and 11.85 and 4.23 mu mol m(-2) for P-ch itin, P-chitin exerted a potent inhibitory effect on the seeded growth of hydroxyapatite from a supersaturated solution, reducing the initia l rate of crystallization by more than 90% at a solution concentration of 10(-4) M. Both chitin derivatives also retarded the rate of sponta neous calcium phosphate precipitation. The type of calcium phosphate p recipitated was poorly crystallized, calcium-deficient apatite. The ch itin derivatives were found to be incorporated into the precipitate an d influenced both the phase and morphology of calcium phosphate formed . (C) 1998 Published by Elsevier Science Ltd. All rights reserved.