Transportable hyperpolarized metabolites

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Transportable hyperpolarized metabolites, Nature Communications 8, Article number: 13975 (2017)

 

Dissolution dynamic nuclear polarization (d-DNP) is a powerful method to enhance nuclear magnetic resonance (NMR) signals by several orders of magnitude, notably in 13C-labelled metabolites. The production of 13C-hyperpolarized metabolites has opened the way to a broad range of novel experiments, such as the detection of intermediates in fast chemical reactions the observation of protein folding in real time or the detection and monitoring of cancer in humans. In d-DNP experiments, the 13C metabolites are usually polarized at low temperatures (1.2 - 4.2 K) and moderate fields (usually 3.35 - 6.7 T) either directly6 or indirectly by 1H-13C cross-polarization (CP). The sample formulation usually consists of a homogeneous aqueous mixture of paramagnetic polarizing agents (PAs) and metabolites sometimes containing a glass-forming agent such as glycerol. The frozen solution is then dynamically polarized by microwave irradiation. The formation of a glass upon freezing is critical for efficient DNP. Alternatively, the PAs can be covalently attached to the surface of mesostructured materials that are impregnated with aqueous solutions of metabolites, in which case one can dispense with glass-forming agents. The PAs may also be generated in situ by ultraviolet irradiation16. However, intimate contact of the nuclear spins with the PA leads to paramagnetic relaxation that is exacerbated at low fields and thus requires dissolution of the sample directly in the cryostat. Hyperpolarized solutions have lifetimes T1(13C)B30–60 s in carboxyl groups that are sufficiently long for immediate imaging or spectroscopy, but not for transport of the sample to a distant user site.

 

 

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Nature Communications 8, Article number: 13975 (2017)

 

Nuclear spin hyperpolarization of 13C-labelled metabolites by dissolution dynamic nuclear polarization can enhance the NMR signals of metabolites by several orders of magnitude, which has enabled in vivo metabolic imaging by MRI. However, because of the short lifetime of the hyperpolarized magnetization (typically o1 min), the polarization process must be carried out close to the point of use. Here we introduce a concept that markedly extends hyperpolarization lifetimes and enables the transportation of hyperpolarized metabolites. The hyperpolarized sample can thus be removed from the polarizer and stored or transported for use at remote MRI or NMR sites. We show that hyperpolarization in alanine and glycine survives 16 h storage and transport, maintaining overall polarization enhancements of up to three orders of magnitude.

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Transportable hyperpolarized metabolites

Xiao Ji, Aurélien Bornet, Basile Vuichoud, Jonas Milani, David Gajan, Aaron J. Rossini, Lyndon Emsley, Geoffrey Bodenhausen & Sami Jannin

Nature Communications 8, Article number: 13975 (2017)

doi:10.1038/ncomms13975