THE CHARACTERIZATION OF HYDROXYAPATITE PREPARATIONS

Hydroxyapatite (HAP) crystals were precipitated by titration methods using solutions of different composition. Each preparation was analyzed for surface area, calcium to phosphate ratio, and mineralization kinetics, by X-ray, scanning, and transmission microscopy, using a constant composition method. The uptake of human serum albumin (HSA) was also determined in order to compare the surface properties of the crystals. All preparations were shown by X ray to have HAP as the only calcium phosphate phase present. In all cases, preparations made by slow titration at high pH and elevated temperature had calcium to phosphate ratios closest to HAP. The lower calcium/phosphate ratios in apatites made by rapid precipitation indicated the formation of calcium deficient apatites. Although the preparations had large differences in crystal size and surface area, the crystal growth rates in supersaturated solutions were very similar, as were the adsorption results. © 1993 Academic Press, Inc.