Aqueous, Heterogeneous para-Hydrogen-Induced 15N Polarization

The successful transfer of para-hydrogen-induced polarization to N-15 spins using heterogeneous catalysts in aqueous solutions was demonstrated. Hydrogenation of a synthesized unsaturated N-15-labeled precursor (neurine) with parahydrogen (p-H-2) over Rh/TiO2 heterogeneous catalysts yielded a hyperpolarized structural analogue of choline. As a result, N-15 polarization enhancements of over 2 orders of magnitude were achieved for the N-15-labeled ethyltrimethylammonium ion product in deuterated water at elevated temperatures. Enhanced N-15 NMR spectra were successfully acquired at 9.4 and 0.05 T. Importantly, long hyperpolarization lifetimes were observed at 9.4 T, with a N-15 T-1 of similar to 6 min for the product molecules, and the T-1 of the deuterated form exceeded 8 min. Taken together, these results show that this approach for generating hyperpolarized species with extended lifetimes in aqueous, biologically compatible solutions is promising for various biomedical applications.