title: The status of strontium in biological apatites: an XANES investigation.
abstract: Osteoporosis represents a major public health problem and increases patient morbidity through its association with fragility fractures. Among the different treatments proposed, strontium-based drugs have been shown to increase bone mass in postmenopausal osteoporosis patients and to reduce fracture risk. While the localization of Sr(2+) cations in the bone matrix has been extensively studied, little is known regarding the status of Sr(2+) cations in natural biological apatite. In this investigation the local environment of Sr(2+) cations has been investigated through XANES (X-ray absorption near-edge structure) spectroscopy in a set of pathological and physiological apatites. To assess the localization of Sr(2+) cations in these biological apatites, numerical simulations using the ab initio FEFF9 X-ray spectroscopy program have been performed. The complete set of data show that the XANES part of the absorption spectra may be used as a fingerprint to determine the localization of Sr(2+) cations versus the mineral part of calcifications. More precisely, it appears that a relationship exists between some features present in the XANES part and a Sr(2+)/Ca(2+) substitution process in site (I) of crystal apatite. Regarding the data, further experiments are needed to confirm a possible link between the relationship between the preparation mode of the calcification (cellular activity for physiological calcification and precipitation for the pathological one) and the adsorption mode of Sr(2+) cations (simple adsorption or insertion). Is it possible to draw a line between life and chemistry through the localization of Sr in apatite? The question is open for discussion. A better structural description of these physiological and pathological calcifications will help to develop specific therapies targeting the demineralization process in the case of osteoporosis.
authors: Laboratoire de Physique des Solides, Bâtiment 510, Université Paris XI, 91405 Orsay, France. bazin@lps.u-psud.fr
authors: D
authors: D
authors: Bazin
authors: M
authors: M
authors: Daudon
authors: Ch
authors: Ch
authors: Chappard
authors: J J
authors: JJ
authors: Rehr
authors: D
authors: D
authors: Thiaudière
authors: S
authors: S
authors: Reguer
mesh_terms: D001031:Apatites / Q000737:chemistry*; D001842:Bone and Bones / Q000737:chemistry*; D002413:Cations, Divalent / Q000737:chemistry; D005260:Female; D006801:Humans; D007669:Kidney Calculi / Q000737:chemistry*; D010024:Osteoporosis / Q000188:drug therapy; D015663:Osteoporosis, Postmenopausal / Q000188:drug therapy; D013324:Strontium / Q000737:chemistry*; D056928:X-Ray Absorption Spectroscopy
chemical_list: D001031:Apatites; D002413:Cations, Divalent; D013324:Strontium