Aqueous, Heterogeneous para-Hydrogen-Induced (15)N Polarization

[Image: see text] The successful transfer of para-hydrogen-induced polarization to (15)N spins using heterogeneous catalysts in aqueous solutions was demonstrated. Hydrogenation of a synthesized unsaturated (15)N-labeled precursor (neurine) with parahydrogen (p-H(2)) over Rh/TiO(2) heterogeneous catalysts yielded a hyperpolarized structural analogue of choline. As a result, (15)N polarization enhancements of over 2 orders of magnitude were achieved for the (15)N-labeled ethyltrimethylammonium ion product in deuterated water at elevated temperatures. Enhanced (15)N NMR spectra were successfully acquired at 9.4 and 0.05 T. Importantly, long hyperpolarization lifetimes were observed at 9.4 T, with a (15)N T(1) of ∼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.