Room temperature synthesis of highly hemocompatible hydroxyapatite, study of their physical properties and spectroscopic correlation of particle size.

Needle shaped nanoparticles of hydroxyapatite (HA) have been synthesized at room temperature using orthophosphoric acid as the source of (PO4)3- ions, while calcium chloride, the calcium source, is suitably complexed with citric acid/tartaric acid/acetic acid. The presence of ligands inhibits the growth along [001] and [100] directions of the crystal and thus, helps in formation of needle shaped nanoparticles. The chemical compositions of the samples have been established through AAS and FTIR spectroscopy, while the crystallinity has been assessed through XRD and by the spectral changes in the υ1 and υ3 frequencies of the phosphate group in the respective FTIR spectra. The particle sizes of the samples have been determined from line broadening studies and correlations have been established between the curve fitted percentage area of FTIR and full width half height (FWHH) of the XRD peaks. TEM studies revealed the particle to be needle-shaped with a length and diameter in the range of 20-65 nm and 4-11 nm respectively. Changes in the surface charge of the water dispersed HA samples have been determined at different pH and the isoelectric point for the samples have been found in the range of 3.1-3.4. Finally, the morphology, surface area and hemocompatibility characteristics of the HA samples, prepared by using different complexing agents, have been compared.