Synthesis and Characterization of Hydroxyapatite Crystals

Pentacalcium hydroxide phosphate, or hydroxyapatite, is an important biological apatite found in tooth enamel and bone. Hydroxyapatite is used as a biomaterial to replace hard tissues, and as such, is useful synthetically. However, some synthetic hydroxyapatite crystals have too low of a fracture toughness to be viable for weight-bearing bone grafts. Acicular, or needle-like, hydroxyapatite crystals have been found to have higher fracture toughness than other crystal formations. For this reason, it is useful to focus on the synthesis of needle-like hydroxyapatite crystals. In this research, hydroxyapatite was synthesized with variable calcium to phosphorous ratios in order to investigate the effects of stoichiometry on crystal habit. It was found that the calcium to phosphorous ratio affected the crystal habit of synthetic hydroxyapatite crystals, which was then related to supersaturation values calculated with aqueous speciation software (OLI Systems). The crystals were identified to be hydroxyapatite through X-ray diffraction and characterized with optical microscopy. Future work will focus on synthesizing transition-metal complexed hydroxyapatite, and further characterization studies