title: The status of strontium in biological apatites: an XANES/EXAFS investigation.
abstract: Osteoporosis represents a major public health problem through its association with fragility fractures. The public health burden of osteoporotic fractures will rise in future generations, due in part to an increase in life expectancy. Strontium-based drugs have been shown to increase bone mass in postmenopausal osteoporosis patients and to reduce fracture risk but the molecular mechanisms of the action of these Sr-based drugs are not totally elucidated. The local environment of Sr(2+) cations in biological apatites present in pathological and physiological calcifications in patients without such Sr-based drugs has been assessed. In this investigation, X-ray absorption spectra have been collected for 17 pathological and physiological calcifications. These experimental data have been combined with a set of numerical simulations using the ab initio FEFF9 X-ray spectroscopy program which takes into account possible distortion and Ca/Sr substitution in the environment of the Sr(2+) cations. For selected samples, Fourier transforms of the EXAFS modulations have been performed. The complete set of experimental data collected on 17 samples indicates that there is no relationship between the nature of the calcification (physiological and pathological) and the adsorption mode of Sr(2+) cations (simple adsorption or insertion). Such structural considerations have medical implications. Pathological and physiological calcifications correspond to two very different preparation procedures but are associated with the same localization of Sr(2+) versus apatite crystals. Based on this study, it seems that for supplementation of Sr at low concentration, Sr(2+) cations will be localized into the apatite network.
authors.affiliation: CNRS-LCMCP-UPMC, Collège de France, 11 place Marcelin Berthelot, 75231 Paris Cedex 05, France.
authors.forename: Dominique
authors.initials: D
authors.lastname: Bazin
authors.affiliation: Laboratoire de Physique des Solides, Université Paris XI, Bâtiment 510, 91405 Orsay, France.
authors.forename: Arnaud
authors.initials: A
authors.lastname: Dessombz
authors.affiliation: INSERM, UMR-S 606, Lariboisière Hospital, F-75010 Paris, France.
authors.forename: Christelle
authors.initials: C
authors.lastname: Nguyen
authors.affiliation: INSERM, UMR-S 606, Lariboisière Hospital, F-75010 Paris, France.
authors.forename: Hang Korng
authors.initials: HK
authors.lastname: Ea
authors.affiliation: INSERM, UMR-S 606, Lariboisière Hospital, F-75010 Paris, France.
authors.forename: Frédéric
authors.initials: F
authors.lastname: Lioté
authors.affiliation: Department of Physics, University of Washington, Seattle, WA 98195, USA.
authors.forename: John
authors.initials: J
authors.lastname: Rehr
authors.affiliation: B2OA, UMR 7052 CNRS, Université Paris Diderot, 10 avenue de Verdun, F-75010 Paris, France.
authors.forename: Christine
authors.initials: C
authors.lastname: Chappard
authors.affiliation: Laboratoire de Physique des Solides, Université Paris XI, Bâtiment 510, 91405 Orsay, France.
authors.forename: Stephan
authors.initials: S
authors.lastname: Rouzière
authors.affiliation: Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin, BP 48, 91192 Gif-sur-Yvette, France.
authors.forename: Dominique
authors.initials: D
authors.lastname: Thiaudière
authors.affiliation: Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin, BP 48, 91192 Gif-sur-Yvette, France.
authors.forename: Solen
authors.initials: S
authors.lastname: Reguer
authors.affiliation: Service d'Explorations Fonctionnelles, AP-HP, Hôpital Tenon, 4 rue de la Chine, F-75020 Paris, France.
authors.forename: Michel
authors.initials: M
authors.lastname: Daudon
mesh_terms: D001031:Apatites / Q000737:chemistry*; D002113:Calcification, Physiologic; D002114:Calcinosis; D006801:Humans; D013052:Spectrometry, X-Ray Emission / Q000379:methods*; D013324:Strontium / Q000032:analysis*; D056928:X-Ray Absorption Spectroscopy / Q000379:methods*
chemical_list: D001031:Apatites; D013324:Strontium
keywords: Ca phosphate apatites; Fourier transform infrared spectroscopy; X-ray absorption spectroscopy; pathological calcifications; physiological calcifications; strontium environment