A copper-containing analog of the biomineral whitlockite: dissolution-precipitation synthesis, structural and biological properties.

In the present work, copper whitlockite (Cu-WH, Ca 18 Cu 2 (HPO 4 ) 2 (PO 4 ) 12 ) was successfully synthesized and comprehensively characterized, founding the base knowledge for its future studies in medicine, particularly for bone regeneration. This material is a copper-containing analog of the well-known biomineral magnesium whitlockite (Mg-WH, Ca 18 Mg 2 (HPO 4 ) 2 (PO 4 ) 12 ). The synthesis of powders was performed by a dissolution-precipitation method in an aqueous medium under hydrothermal conditions. Phase conversion from brushite (CaHPO 4 ·2H 2 O) to Cu-WH took place in an acidic medium in the presence of Cu 2+ ions. Optimization of the synthesis conditions in terms of medium pH, temperature, time, Ca/Cu molar ratio and concentration of starting materials was performed. The crystal structure of the synthesized products was confirmed by XRD, FTIR and Raman spectroscopy, 1 H and 31 P solid-state NMR, and EPR. Morphological features and elemental distribution of the synthesized powders were studied by means of SEM/EDX analysis. The ion release in SBF solution was estimated using ICP-OES. Cytotoxicity experiments were performed with MC3T3-E1 cells. The study on thermal stability revealed that the synthesized material is thermally unstable and gradually decomposes upon annealing to Cu-substituted β-Ca 3 (PO 4 ) 2 and Ca 2 P 2 O 7 .