Enhancing the MRI Signals of Metabolic Biosensors by >10,000-fold via Dissolution Dynamic Nuclear Polarization*

Dynamic nuclear polarization (DNP) via the dissolution method is a technique that allows the production of highly-amplified or "hyperpolarized" liquid-state nuclear magnetic resonance (NMR) or magnetic resonance imaging (MRI) signals with >10,000-fold enhancement at physiologically tolerable temperatures. The NMR amplification process occurs at cryogenic temperature and high magnetic field where the electron spin polarization is almost 100%, in which slightly off-resonance microwave irradiation is employed to tranfer the high electron polarization to the nuclear spins. A dissolution device is then inserted into the cryostat to rapidly dissolved the frozen polarized solid into hyperpolarized liquid. With the relatively long liquid-state spin-lattice relaxation time T1 of the chosen target nuclei, most of the enhanced or hyperpolarized NMR signal of the nuclei is preserved in room temperature. Armed with >10,000-fold MRI signal enhancement, this allows for highly sensitive and real-time MRI tracking of the metabolic fates of MRI biosensors for diagnostic biochemical imaging of a number of pathologies including cancer. Details of the instrumental process and biomedical examples will be discussed.