From crystalline to amorphous calcium pyrophosphates: a solid state Nuclear Magnetic Resonance perspective

Pierre Gras (1) , Annabelle Baker (2) , Christèle Combes (1) , Christian Rey (1) , Stéphanie Sarda (1) , Adrian J. Wright (2) , Mark E. Smith (3, 4) , John V. Hanna (3) , Christel Gervais (5) , Danielle Laurencin (6) , Christian Bonhomme (5)

1 CIRIMAT - Centre interuniversitaire de recherche et d'ingenierie des matériaux
2 School of Chemistry
3 Department of Physics [Coventry]
4 Vice-Chancellor’s Office - University House
5 SMiLES - Spectroscopie, Modélisation, Interfaces pour L'Environnement et la Santé
6 ICGM - Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier

Hydrated calcium pyrophosphates (CPP, Ca2P2O7·nH2O) are a fundamental family of materials among osteoarticular pathologic calcifications. In this contribution, a comprehensive multinuclear NMR (Nuclear Magnetic Resonance) study of four crystalline and two amorphous phases of this family is presented. 1H, 31P and 43Ca MAS (Magic Angle Spinning) NMR spectra were recorded, leading to informative fingerprints characterizing each compound. In particular, different 1H and 43Ca solid state NMR signatures were observed for the amorphous phases, depending on the synthetic procedure used. The NMR parameters of the crystalline phases were determined using the GIPAW (Gauge Including Projected Augmented Wave) DFT approach, based on first–principles calculations. In some cases, relaxed structures were found to improve the agreement between experimental and calculated values, demonstrating the importance of proton positions and pyrophosphate local geometry in this particular NMR crystallography approach. Such calculations serve as a basis for the future ab initio modeling of the amorphous CPP phases.

Mots clés: 43Ca solid state NMR; 1H; 31P; Crystalline calcium pyrophosphates; Amorphous calcium pyrophosphates; First principles GIPAW calculations

Domaines: Rhumatologie et système ostéo-articulaire; Biomatériaux

Pierre Gras, Annabelle Baker, Christèle Combes, Christian Rey, Stéphanie Sarda, et al.. From crystalline to amorphous calcium pyrophosphates: a solid state Nuclear Magnetic Resonance perspective. Acta Biomaterialia, 2016, 31, pp.348-357. ⟨10.1016/j.actbio.2015.10.016⟩. ⟨hal-01221038⟩