Surface modification of zinc-containing hydroxyapatite by tartaric acid

The surface of Zn-substituted hydroxyapatites (Ca(10−x)Znx(PO4)6(OH)2, with 0 ≤ x ≤ 2, CaxZnxHA) modified by tartaric acid was investigated by various techniques. XRD powder patterns revealed that synthesized samples were single phase of HA with broadened XRD reflections. FTIR and (13C, 1H and 31P) MAS NMR measurements confirmed the grafting of the tartaric acid on the apatite surface. Chemical analysis showed that for ZnHA the grafted acid amount increases with the increase of the acid concentration in the starting solutions, while for HA, it remained constant, indicating more reactivity for ZnHA surface. A mechanism of surface modification is proposed based on the obtained results.