Abstract: In order to further understand the formation mechanism of natural bone and to prepare better biomimetic biomaterials with high performance, three kinds of self-assemble organic films with different head groups and three kinds of inorganic ions existing in the body fluid, were used to study the growth behavior of HAP crystal by X-ray diffraction(XRD), scanning electron microscopy(SEM). The results show that, 1) the presence of organic films can accelerate the HAP crystal nucleation, but different organic film can induce HAP crystal with different growth style and crystal morphology. The HAP induced by the film with —NH₂ head groups is the nano-platelet crystal with regular orientation and order array. On the film with —SO₃^2- head groups, radiated growth style of HAP crystal is mediated. While the HAP crystal induced by the film with —PO₄^3- head groups has neither regular orientation nor order growth style. 2) The inorganic ions of the calcification solution play great roles in controlling HAP crystal growth rate and morphology. Platelet-shape HAP crystal is always formed in the presence of Cl^- ions by exchanging site with OH^- ions. Mg²⁺ ions can inhabite the HAP crystal nucleation and growth rate due to Mg²⁺ taking up the nucleation site of organic film or the growth site of HAP surface, while in the presence of SO₄^2- ions, HAP crystal grows with the style of cluster shape and its size is very little due to SO₄^2- ions absorbing on the surface of HAP crystal.

Key words: biominerialization; self-assembled organic film; hydroxyapatite; crystal growth