Hydrogen-substituted ?-tricalcium phosphate synthesized in organic media.

ABSTRACT: ?-Tricalcium phosphate (?-TCP) platelets synthesized in ethylene glycol offer interesting geometries for nano-structured composite bone substitutes but were never crystallographically analyzed. In this study, powder X-ray diffraction and Rietveld refinement revealed a discrepancy between the platelet structure and the known ?-TCP crystal model. In contrast, a model featuring partial H for Ca substitution and the inversion of P1O₄ tetrahedra, adopted from the whitlockite structure, allowed for a refinement with minimal misfits and was corroborated by HPO₄^2- absorptions in Fourier-transform IR spectra. The Ca/P ratio converged to 1.443?±?0.003 (n = 36), independently of synthesis conditions. As a quantitative verification, the platelets were thermally decomposed into hydrogen-free ?-TCP and ?-calcium pyrophosphate which resulted in a global Ca/P ratio in close agreement with the initial ?-TCP Ca/P ratio (?Ca/P = 0.003) and with the chemical composition measured by inductively coupled plasma (?Ca/P = 0.003). These findings thus describe for the first time a hydrogen-substituted ?-TCP structure, i.e. a Mg-free whitlockite, represented by the formula Ca_21?-?x(HPO₄)_2x(PO₄)_14?-?2x, where x = 0.80?±?0.04, and may have implications for resorption properties of bone regenerative materials.

SUBMITTER: Stahli C 

PROVIDER: S-EPMC5134762 | biostudies-literature | 2016 Dec

REPOSITORIES: biostudies-literature