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

RL Karlinsey, K Yi, CW Duhn. Nucleation and growth of apatite by a self-assembled polycrystalline bioceramic. Bioinspiration & Biomimetics 1, 12 (2006).


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.


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Robert L. Karlinsey, PhD

Dr. Robert L. Karlinsey earned a BS in Physics and PhD in Chemical Physics, holds several patents, and has published in multiple fields including dentistry, chemistry, and materials science. His lifelong struggles with his own dental decay ultimately inspired him to investigate the remineralization of teeth.