Assessing the onset of calcium phosphate nucleation by hyperpolarized real-time NMR

Emmanuelle M M Weber (1) , Thomas Kress (2) , Daniel Abergel (1) , Steffi Sewsurn (3) , Thierry Azaïs (4) , Dennis Kurzbach (2)

1 LBM UMR 7203 - Laboratoire des biomolécules
2 University of Vienna [Vienna]
3 LCMCP - Laboratoire de Chimie de la Matière Condensée de Paris
4 LCMCP-SMiLES - Spectroscopie, Modélisation, Interfaces pour L'Environnement et la Santé

We report an experimental approach for highresolution real-time monitoring of transiently formed species occurring during the onset of precipitation of ionic solids from solution. This is made possible by real-time nuclear magnetic resonance (NMR) monitoring using dissolution dynamic nuclear polarization (D-DNP) to amplify signals of functional intermediates and is supported by turbidimetry, cryo-electron microscopy and solid-state NMR measurements. D-DNP can provide drastic signal improvements in NMR signal amplitudes, permitting dramatic reductions in acquisition times and thereby enabling to probe fast interaction kinetics such as those underlying the formation of pre-nucleation species (PNS) that precede solid-liquid phase separation. This experimental strategy allows, at unprecedented detail, for investigation of the formation of calcium phosphate (CaP)-based minerals by 31 P NMR-a process of substantial industrial, geological, and biological interest. So far, many aspects of the mechanisms of CaP nucleation remain unclear due to the absence of experimental methods capable of accessing such processes on sufficiently short time scales. The approach reported here aims to address this by an improved characterization of the initial steps of CaP precipitation, permitting the detection of PNS by NMR and determination of their formation rates, exchange dynamics and sizes. Using D-DNP monitoring, we find that under our conditions i) in the first 2 seconds after preparation of oversaturated calcium phosphate solutions, PNS with a hydrodynamic radius of Rh ≈ 1 nm are formed; and ii) following this rapid initial formation, the entire crystallization processes proceed on considerably longer timescales, requiring > 20 s to form the final crystal phase.

Domaines: Chimie

Emmanuelle M M Weber, Thomas Kress, Daniel Abergel, Steffi Sewsurn, Thierry Azaïs, et al.. Assessing the onset of calcium phosphate nucleation by hyperpolarized real-time NMR. Analytical Chemistry, 2020, 92 (11), pp.7666-7673. ⟨10.1021/acs.analchem.0c00516⟩. ⟨hal-03100940⟩