87Sr Solid-State NMR as a Structurally Sensitive Tool for the Investigation of Materials: Antiosteoporotic Pharmaceuticals and Bioactive Glasses

• Published in: Journal of the American Chemical Society 2012-08, Vol.134 (30), p.12611-12628
• Main Authors: Bonhomme, Christian, Gervais, Christel, Folliet, Nicolas, Pourpoint, Frédérique, Coelho Diogo, Cristina, Lao, Jonathan, Jallot, Edouard, Lacroix, Joséphine, Nedelec, Jean-Marie, Iuga, Dinu, Hanna, John V, Smith, Mark E, Xiang, Ye, Du, Jincheng, Laurencin, Danielle
• Format: Article
• Language: English
• Subjects: Biocompatible Materials - chemistry; Glass - chemistry; Magnetic Resonance Spectroscopy - methods; Malonates - chemistry; Models, Molecular; Pharmaceutical Preparations - chemistry; Strontium - analysis; Strontium Isotopes - analysis
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja303505g

Strontium is an element of fundamental importance in biomedical science. Indeed, it has been demonstrated that Sr2+ ions can promote bone growth and inhibit bone resorption. Thus, the oral administration of Sr-containing medications has been used clinically to prevent osteoporosis, and Sr-containing biomaterials have been developed for implant and tissue engineering applications. The bioavailability of strontium metal cations in the body and their kinetics of release from materials will depend on their local environment. It is thus crucial to be able to characterize, in detail, strontium environments in disordered phases such as bioactive glasses, to understand their structure and rationalize their properties. In this paper, we demonstrate that 87Sr NMR spectroscopy can serve as a valuable tool of investigation. First, the implementation of high-sensitivity 87Sr solid-state NMR experiments is presented using 87Sr-labeled strontium malonate (with DFS (double field sweep), QCPMG (quadrupolar Carr–Purcell–Meiboom–Gill), and WURST (wideband, uniform rate, and smooth truncation) excitation). Then, it is shown that GIPAW DFT (gauge including projector augmented wave density functional theory) calculations can accurately compute 87Sr NMR parameters. Last and most importantly, 87Sr NMR is used for the study of a (Ca,Sr)-silicate bioactive glass of limited Sr content (only ∼9 wt %). The spectrum is interpreted using structural models of the glass, which are generated through molecular dynamics (MD) simulations and relaxed by DFT, before performing GIPAW calculations of 87Sr NMR parameters. Finally, changes in the 87Sr NMR spectrum after immersion of the glass in simulated body fluid (SBF) are reported and discussed.