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Photogenerated Radical in Phenylglyoxylic Acid for in Vivo Hyperpolarized 13C MR with Photosensitive Metabolic Substrates


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Authors

Marco Rius, Irene 
Cheng, Tian 
Gaunt, AP 
Patel, Saket 

Abstract

Whether for 13C magnetic resonance studies in chemistry, biochemistry or biomedicine, hyperpolarization methods based on dynamic nuclear polarization (DNP) have become ubiquitous. DNP requires a source of unpaired electrons, which are commonly added to the sample to be hyperpolarized in the form of stable free radicals. Once polarized, the presence of these radicals is unwanted. These radicals can be replaced by nonpersistent radicals created by photo-irradiation of pyruvic acid (PA), which are annihilated upon dissolution or thermalization in the solid state. However, since PA is readily metabolized by most cells, its presence may be undesirable for some metabolic studies. In addition, some 13C substrates are photo-sensitive and, therefore, may degrade during photo-generation of PA radical, which requires ultraviolet (UV) light. We show here that photoirradiation of phenylglyoxylic acid (PhGA) using visible light produces a non-persistent radical that, in principle, can be used to hyperpolarize any molecule. We compare radical yields in samples containing PA and PhGA upon photo-irradiation with broadband and narrowband UV-visible light sources. To demonstrate the suitability of PhGA as a radical precursor for DNP, we polarized the gluconeogenic probe 13C-dihydroxyacetone, which is UV-sensitive, using a commercial 3.35 T DNP polarizer and then injected this into a mouse and followed its metabolism in vivo.

Description

Keywords

34 Chemical Sciences, 3406 Physical Chemistry

Journal Title

Journal of the American Chemical Society

Conference Name

Journal ISSN

1520-5126
1520-5126

Volume Title

Publisher

American Chemical Society (ACS)
Sponsorship
Cancer Research Uk (None)
European Commission Horizon 2020 (H2020) Marie Sk?odowska-Curie actions (642773)
Cancer Research UK (CB4100)
Cancer Research UK (C14303/A17197)
European Research Council (682574)
Cancer Research UK (17242)
This work is part of a project that has received funding from the European Union’s Horizon 2020 European Research Council (ERC Consolidator Grant) under grant agreement no. 682574 (ASSIMILES). Funding was also received from a Cancer Research UK Programme grant (17242) and from the CRUK-EPSRC Imaging Centre in Cambridge and Manchester (16465). F.K. and S.P. received funding from the European Union’s Horizon 2020 Research and Innovation Program under Marie Sklodowska-Curie grant agreement no. 642773 (EUROPOL). A. Capozzi received funding from the European Union’s Horizon 2020 Research and Innovation Program under Marie Sklodowska-Curie grant agreement no. 713683 (COFUNDfellowsDTU).