Synthesis and physicochemical characterization of Zn-doped brushite

Abstract Dicalcium phosphate dihydrate (DCPD) enriched by different amounts of Zn2+ ions was synthesized in aqueous solution via standard precipitation method. The obtained powders were characterised by powder X-ray diffractometry (PXRD), infrared spectroscopy (FT-IR), solid-state nuclear magnetic resonance (ssNMR), inductively coupled plasma optical emission spectroscopy (ICP-OES) and scanning electron microscopy (SEM). These tests confirmed that all the powders were highly microcrystalline brushite. As the concentration of zinc increased, an additional crystalline phase of α-hopeite appeared, and, simultaneously, the crystallinity of brushite slightly decreased. Moreover, according to the shifts of PXRD, FTIR and 31P ssNMR line positions, it was proved that zinc ions were successfully introduced into the crystal of DCPD. The (Ca+Zn)/P molar ratio calculated from ICP-OES results was ca. 1.0, which is typical for DCPD; only the (Ca+Zn)/P molar ratio of the sample with the highest concentration of Zn slightly differs, which was caused by the presence of α-hopeite. SEM images have shown a high tendency of Zn-containing brushite to agglomerate into the spherical, compact clusters. The preliminary biological tests have shown that the powders are non-toxic, which makes them promising materials for potential use in mineralised tissue engineering.