Laboratoire de Physique des Solides, Bâtiment 510, Université Paris XI, 91405 Orsay, France.
J Synchrotron Radiat. 2011 Nov;18(Pt 6):912-8. doi: 10.1107/S0909049511032651. Epub 2011 Sep 16.
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.
骨质疏松症是一个主要的公共卫生问题，它与脆性骨折的发生有关，增加了患者的发病率。在提出的各种治疗方法中，锶基药物已被证明能增加绝经后骨质疏松症患者的骨量，并降低骨折风险。虽然已经对 Sr(2+) 阳离子在骨基质中的定位进行了广泛研究，但对于天然生物磷灰石中 Sr(2+) 阳离子的状态知之甚少。在这项研究中，通过 X 射线吸收近边结构（XANES）光谱法研究了一组病理性和生理性磷灰石中 Sr(2+) 阳离子的局部环境。为了评估 Sr(2+) 阳离子在这些生物磷灰石中的定位，使用从头算 FEFF9 射线光谱程序进行了数值模拟。完整的数据集表明，吸收光谱的 XANES 部分可作为指纹，用于确定 Sr(2+) 阳离子相对于钙化矿物部分的定位。更准确地说，似乎在 XANES 部分存在的某些特征与晶体磷灰石中位点（I）的 Sr(2+)/Ca(2+) 取代过程之间存在关系。关于这些数据，需要进一步的实验来证实钙化（生理钙化的细胞活动和病理钙化的沉淀）的制备模式与 Sr(2+) 阳离子的吸附模式（简单吸附或插入）之间可能存在的关系。是否可以通过磷灰石中 Sr 的定位在生命和化学之间划一条线？这个问题有待讨论。对这些生理和病理钙化进行更好的结构描述将有助于针对骨质疏松症脱矿过程开发特定的治疗方法。
