Nucleation and growth of apatite by a self-assembled polycrystalline bioceramic

作者：Karlinsey Robert L^*; Yi Keewook; Duhn Clif W

来源：Bioinspiration & Biomimetics, 2006, 1(1): 12-19.

DOI：10.1088/1748-3182/1/1/002

The formation aspects of a polycrystalline self-assembled bioceramic leading to the nucleation of hard-tissue mineral from a supersaturated solution are discussed. Scanning electron imaging and surface-sensitive interrogations of the nucleated mineral indicated the presence of an intermediate amorphous layer encompassing a rather crystalline phase that formed on niobium oxide (Nb2O5) microstructures. The crystalline phase was identified from Raman spectroscopy as hydroxyapatite (HAP), while the phosphorous-rich amorphous layer is suggested to have the chemical form CaO-P2O5. In addition, the mechanism favoring HAP nucleation is discussed in terms of the (002) and (001) diffraction planes of HAP and Nb2O5, respectively. The small mismatch along several lattice dimensions strongly suggests epitaxy as a dominant mode in the heterogeneous nucleation of HAP. Furthermore, the effectiveness of this mode was shown to critically depend on the self-organization of the Nb2O5 microstructures. Because nucleation does not appear to depend solely on the integrity of Nb2O5 crystals, the self-organization of Nb2O5 crystals also contributes significantly to HAP nucleation. Based on our results, we propose the organized arrangement of bioceramic crystals as a new mode for the bioinspiration of hydroxyapatite and other hard-tissue mineral.