The effect of acidic amino acids on hydroxyapatite crystallization

Crystallization kinetics of hydroxyapatite, HAP, in the presence of acidic amino acids (aspartic and glutamic acid) were investigated at conditions of sustained supersaturation. In the presence of both aspartic and glutamic a cid, the crystal growth rates of HAP decreased markedly. Their action is du e to adsorption and subsequent blocking of the active growth sites onto the surface of the HAP crystals. The kinetic results revealed that a Langmuir- type adsorption isotherm is followed and affinity constants of both amino a cids for HAP crystal surface were calculated. The apparent order of the cry stal growth reaction was found to be equal to 2, suggesting a surface diffu sion controlled mechanism. (C) 2000 Elsevier Science B.V. All rights reserv ed.