Synthesis of hydroxyapatite nanoparticles with tailorable morphologies and carbonate substitutions using a wet precipitation method

Hydroxyapatite (HA) nanoparticles with different morphologies and variant levels of carbonate substitutions were synthesized using a wet precipitation method by adjusting the heating temperature and/or the initial ion concentration of the reaction system. Within the particles, crystalline domains with different lengths were aligned along each other and formed into nanoparticles with different sizes, shapes and topographies. Different from most reported studies, the nucleation, growth and morphology of the crystalline domains were found sensitive to heating temperature, but not significantly influenced by initial ion concentration within the studied range. The OH- and PO4(3-) ions within the HA particles were partially substituted by CO3(2-) ions. The substitution was dominated by the replacement of OH- instead of PO4(3-) in HA. The carbonate substitution was found to decrease with increasing heating temperature and/or initial ion concentration. Therefore, both the morphology and composition of the HA particles can be tailored by controlling the heating temperature and/or the initial ion concentration in the reaction system. Such synthesized HA nanoparticles can be used as biomaterials for bone tissue engineering.