Aqueous, Heterogeneous para-Hydrogen-Induced 15N Polarization

The successful transfer of parahydrogen-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 analog of choline. As a result, 15 N polarization enhancements of over two orders of magnitude were achieved for the 15 N-ethyl trimethyl ammonium ion product in deuterated water at elevated temperatures. Enhanced 15 N NMR spectra were successfully acquired at 9.4 T 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.