Capozzi, A., et al., Liquid-State 13C Polarization of 30% through Photo-Induced Non-Persistent Radicals. The Journal of Physical Chemistry C, 2018.
Hyperpolarization via dissolution Dynamic Nuclear Polarization (dDNP) is crucial to significantly increase the magnetic resonance imaging (MRI) sensitivity, opening up for in vivo real-time MRI using in particular 13C-labelled substrates. The range of applications is however limited by the relatively fast decay of the nuclear spin polarization together with the constraint of having to polarize the spins near the MRI magnet. As recently demonstrated, the employment of UV-induced non-persistent radicals represents an elegant solution to tackle these drawbacks. Nevertheless, since its introduction, the spread of the technique has been prevented by the relatively low achievable polarization, slow buildup time and time-consuming sample preparation. In the present work, thanks to a thorough investigation of the radical generation step, we provide a robust protocol to enhance the efficiency and performance of the UV-radical technique. Under optimal conditions, it was possible to produce up to 60 mM radical in less than 5 min, and reach maximum DNP enhancement with a buildup time constant of approx. 25 min, at 6.7 T and 1 K, resulting in 30% 13C liquid-state polarization.