Magnesium incorporation into hydroxyapatite

Department of Physics, University of Warwick, Coventry CV4 7AL, UK.
Biomaterials (Impact Factor: 8.56). 03/2011; 32(7):1826-37. DOI: 10.1016/j.biomaterials.2010.11.017
Source: PubMed


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.

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Available from: Wojciech Chrzanowski, May 15, 2014
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    • "Mg-HAp was not found in benign lesions whereas it was frequently detected in breast cancer. The capability of HA to bind to bicationic ions such as Mg [40], may confer carcinogenic properties on HA since a Mg-depleted microenvironment can influence the DNA repair processes and the control of proliferation and apoptosis [41,42]. The EDX data allowed us to hypothesize an active role of microcalcifications in breast carcinogenesis, since such complex microcalcifications cannot be due to a mere degenerative process but rather resemble the physiological process of mineralization that occurs in bone. "
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    • ") of Mg in seawater. The phenomenon of Mg substitution of Ca in apatite has been observed analytically and experimentally by biologists and material scientists (Marques de Silva et al. 2010; Laurencin et al. 2011; Aina et al. 2012 ;Shepherd et al. 2012 "
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    • "In this context, Bio-Rad recommends washing the HA with a slightly elevated pH buffer prior to elution with a salt step (surface neutralisation step (SNS)), which has been shown to increase the HA column lifetime by limiting the pH excursions noted above. Recently it has also been shown [29] that the incorporation of magnesium into the HA crystal structure is possible. The Mg ion causes a strong distortion of the environment of the anions , due to the shorter Mg–O distance. "
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