title: Magnesium incorporation into hydroxyapatite.
abstract: The incorporation of Mg in hydroxyapatite (HA) was investigated using multinuclear solid state NMR, X-ray absorption spectroscopy (XAS) and computational modeling. High magnetic field (43)Ca solid state NMR and Ca K-edge XAS studies of a ∼10% Mg-substituted HA were performed, bringing direct evidence of the preferential substitution of Mg in the Ca(II) position. (1)H and (31)P solid state NMR show that the environment of the anions is disordered in this substituted apatite phase. Both Density Functional Theory (DFT) and interatomic potential computations of Mg-substituted HA structures are in agreement with these observations. Indeed, the incorporation of low levels of Mg in the Ca(II) site is found to be more favourable energetically, and the NMR parameters calculated from these optimized structures are consistent with the experimental data. Calculations provide direct insight in the structural modifications of the HA lattice, due to the strong contraction of the M⋯O distances around Mg. Finally, extensive interatomic potential calculations also suggest that a local clustering of Mg within the HA lattice is likely to occur. Such structural characterizations of Mg environments in apatites will favour a better understanding of the biological role of this cation.
authors.affiliation: Department of Physics, University of Warwick, Coventry CV4 7AL, UK. danielle.laurencin@univ-montp2.fr
authors.forename: Danielle
authors.initials: D
authors.lastname: Laurencin
authors.forename: Neyvis
authors.initials: N
authors.lastname: Almora-Barrios
authors.forename: Nora H
authors.initials: NH
authors.lastname: de Leeuw
authors.forename: Christel
authors.initials: C
authors.lastname: Gervais
authors.forename: Christian
authors.initials: C
authors.lastname: Bonhomme
authors.forename: Francesco
authors.initials: F
authors.lastname: Mauri
authors.forename: Wojciech
authors.initials: W
authors.lastname: Chrzanowski
authors.forename: Jonathan C
authors.initials: JC
authors.lastname: Knowles
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Newport
authors.forename: Alan
authors.initials: A
authors.lastname: Wong
authors.forename: Zhehong
authors.initials: Z
authors.lastname: Gan
authors.forename: Mark E
authors.initials: ME
authors.lastname: Smith
mesh_terms: D001672:Biocompatible Materials / Q000737:chemistry; D017886:Durapatite / Q000737:chemistry*; D008274:Magnesium / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D056928:X-Ray Absorption Spectroscopy
chemical_list: D001672:Biocompatible Materials; D017886:Durapatite; D008274:Magnesium