Porous functionalized polymers enable generating and transporting hyperpolarized mixtures of metabolites

Abstract

Hyperpolarization by dissolution dynamic nuclear polarization (dDNP) has enabled promising applications in spectroscopy and imaging, but remains poorly widespread due to experimental complexity. Broad democratization of dDNP could be realized by remote preparation and distribution of hyperpolarized samples from dedicated facilities. Here we show the synthesis of hyperpolarizing polymers (HYPOPs) that can generate radical- and contaminant-free hyperpolarized samples within minutes with lifetimes exceeding hours in the solid state. HYPOPs feature tunable macroporous porosity, with porous volumes up to 80% and concentration of nitroxide radicals grafted in the bulk matrix up to 285 μmol g−1. Analytes can be efficiently impregnated as aqueous/alcoholic solutions and hyperpolarized up to P(13C) = 25% within 8 min, through the combination of 1H spin diffusion and 1H → 13C cross polarization. Solutions of 13C-analytes of biological interest hyperpolarized in HYPOPs display a very long solid-state 13C relaxation times of 5.7 h at 3.8 K, thus prefiguring transportation over long distances.

Signal enhancement of hyperpolarized 15N sites in solution—increase in solid‐state polarization at 3.35 T and prolongation of relaxation in deuterated water mixtures

“…This suggests that the solid‐state T 1 of the 15 N sites investigated here is longer than the 13 C site of [ 13 C]urea (in agreement with the difference between their T 1 values in solution). This observation warrants further investigation and suggests the potential of such compounds to preserve polarization if storage of the polarization is required 31–33 . By fitting the decay of the polarized signal of Sample 1 in Figure 4 and taking into account the effect of 5° excitation pulses, the T 1 of [ 13 C]urea in the solid state was calculated to be about 48 min (Supporting Figure S1).…”

Triplet Dynamic Nuclear Polarization of Guest Molecules through Induced Fit in a Flexible Metal–Organic Framework**

“…Another promising approach is to confine the polarization source and target molecules in the nanopores of porous materials, which is expected to enable hyperpolarization of a variety of guest molecules. Unique DNP systems based on various nanoporous materials have been developed, [8,[25][26][27][28] and our group has also reported triplet-DNP of metal-organic frameworks (MOFs). [29] target guest molecules in nanoporous materials at room temperature.…”

Zero- to Ultralow-Field Nuclear Magnetic Resonance Enhanced with Dissolution Dynamic Nuclear Polarization

“…In order to decrease the polarization losses during sample transfer, some promising methodologies can be implemented: the use of hybrid polarizing solids (HYPSOs) and hyperpolarizing polymers (HYPOPs) avoid the presence of paramagnetic radicals in the sample after dissolution which, as discussed in section III B, induces relaxation and subsequent signal loss [25,[49][50][51].…”

“…Our work on d DNP-ZULF offers competitive proton and carbon polarization and sample concentration, as well as broader applicability of target molecules, compared to techniques using parahydrogen. We expect that d DNP will become a standard choice of hyperpolarization for observing dilute nuclei in zero-field NMR, especially given the recently demonstrated possibility to polarize samples via d DNP in a remote laboratory [25].…”

“…We evaluate paramagnetic relaxation induced by the DNP polarizing agent as a possible reason for the obtained signal enhancement of 11000 while up to >50k could be expected theoretically. We discuss possible improvements of d DNP-ZULF NMR based on recently reported methods such as fast dissolution, transfer, and sample injection [24], as well as the use of filterable polarizing matrices to reduce paramagnetic relaxation [25].…”