Crystal structures of biocompatible Mg-, Zn-, and Co-whitlockites synthesized via one-step hydrothermal reaction

Abstract

Large-scale single crystals of Ca9Mg(PO4)6(PO3OH), Ca9Zn(PO4)6(PO3OH), and Ca9Co(PO4)6(PO3OH) were synthesized using hydrothermal technique, and turned out to be similar to natural bone whitlockite. The hexagonal single crystals about 1 mm with high-quality were obtained with this method for the first time. The crystals were of sufficiently good quality for the precision X-ray structural investigation. The compounds crystallize in usual for this structural type trigonal space group R3c. Presence of hydrogen atom in the structure was confirmed by means of infra-red (IR) spectroscopy, differential scanning calorimetry (DSC) and differential thermogravimetry (DTG) methods. Based on the analysis of the local bond valence sum (BVS), a conclusion on the localization of H atoms was made. The formation of O–H groups and hydrogen bonds H⋯O in vicinity of PO4 tetrahedra was shown and similar to bone whitlockite. This research provides new data on possibility of using hydrothermal technique for obtaining doped bone whitlockites. Hydrogen-containing doped whitlockites can combine bioactive properties and improve biocompatibility due to similarity to natural bond. New structural data are useful for finding the ways to better biocompatibility of whitlockite-based materials.

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

“…In this light, the first row transition metal ions appear to be suitable candidates to form WH structures since their ionic radii are close enough to that of Mg 2+ ions. 20 To the best of our knowledge, currently there are only a few published reports regarding the synthesis and characterization of transition metal WH, including some on Zn-WH, 21–23 Mn-WH, 24,25 and Co-WH 26 and a recently published report on the feasibility of the formation of Cu-WH. 27…”