Hydroxyapatite crystallization on sodium cholate

Bile acids are known to promote pathological calcification in vivo through the formation of their calcium salts. The role of cholic acid's sodium salt regarding its capability of inducing hydroxyapatite was investigated. It w as found that the precipitation of hydroxyapatite was favored by the presen ce of this organic molecule. In this work, the constant composition kinetic s technique was used, which has been proved suitable for the study of the f ormation of a sparingly soluble salts in the presence of another compound. Kinetic analysis of the nucleation rates as a function of the solution supe rsaturation yielded a value of 2 for the number of ions forming the critica l nucleus. It was suggested that the formation of hydroxyapatite is initiat ed via interaction of the calcium ions with the negative end of C = O bond. The apparent order found from kinetics data was 1.7 +/- 0.4 suggesting a s urface diffusion-controlled mechanism. (C) 2001 Elsevier Science B.V. All r ights reserved.