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NMR and MRI are essential measurement techniques in modern chemistry, biology, and medicine, but they have the fatal flaw of being extremely insensitive. Therefore, with MRI, only water, which is abundant in living organisms, can be observed, and with NMR, proteins in cells are difficult to observe due to their low concentration. One of the methods to increase the sensitivity of MRI and NMR at room temperature is triplet-DNP (DNP: dynamic nuclear polarization), which utilizes the photo-excited triplet of molecules.
However, this triplet-DNP has been studied mainly in the field of quantum physics using single crystals, and its application to biology has been difficult. Therefore, we have developed nanomaterials that can transfer polarization to biomolecules and original polarizing agents that can be directly dispersed in water and biomolecules through our unique approach of combining the quantum physics of triplet-DNPs and materials chemistry.
Our goal is to realize innovations by creating ultra-sensitive MRI and NMR.
1. Introduction of material chemistry: use of nanomaterials with large surface area
Conventional triplet-DNP research has used dense organic crystals, but it is difficult to achieve hyperpolarize biomolecules because the target biomolecules to be polarized cannot be introduced into the crystals. As materials chemists, we have introduced nanomaterials with large specific surface area into the field of triplet-DNP. We have succeeded in triplet-DNP of metal-organic frameworks (MOFs) and nanocrystals for the first time, and are challenging to achieve high nuclear polarization of biomolecules and water continuously at room temperature.
【Recent examples】
Triplet-DNP of MOF：J. Am. Chem. Soc. 2018, 140, 15606-15610. Triplet-DNP of guest drugs in MOFs：Angew. Chem. Int. Ed. 2022, 61, e202115792.
Triplet-DNP of water：J. Am. Chem. Soc. 2022, 144, 18023-18029.
2. Original polarizing agnets: enabling high sensitivity for biomolecules and water
In conventional triplet-DNP, only commercially available pentacene has been used as a polarizating agnet, but pentacene is unstable in air and almost insoluble in any solvents. As chemists, we have been developing non-pentacene polarizing agents. We were the first to develop a polarizing agent that is stable in air by adding an electron-withdrawing nitrogen atom, and we were the first to synthesize a water-soluble polarizing agnet and to successfully achieve triplet-DNP of ice. We also succeeded for the first time in triplet-DNP of biomolecules by using a porphyrin derivative as a biocompatible polarizing agent.
【Recent examples】
Air-stale polarizing agent：J. Phys. Chem. Lett. 2019, 10, 2208-2213.
Water-soluble polarizing agent：Chem. Commun. 2020, 56, 3717-3720.
Triplet-DNP of biomolecules：J. Phys. Chem. Lett. 2021, 12, 2645-2650.
Quintet-DNP：Nature Commun. 2023, 14, 1056.
Triplet-DNP of cancer MRI probe, pyruvate：Chem. Sci., 2023, 14, 13842-13850.
Orientation-independent triplet-DNP polarizing agents：Proc. Natl. Acad. Sci. U.S.A., 2023, 120, e2307926120.
Talks about triplet-DNP：
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