Para-hydrogen-induced polarization (PHIP) is a technique capable of producing spin polarization at a magnitude far greater than state-of-the-art magnets. A significant application of PHIP is to generate contrast agents for biomedical imaging. Clinically viable and effective contrast agents not only require high levels of polarization but heterogeneous catalysts that can be used in water to eliminate the toxicity impact. Herein, we demonstrate the use of Pt nanoparticles capped with glutathione to induce heterogeneous PHIP in water. The ligand-inhibited surface diffusion on the nanoparticles resulted in a (1) H polarization of P=0.25% for hydroxyethyl propionate, a known contrast agent for magnetic resonance angiography. Transferring the (1) H polarization to a (13) C nucleus using a para-hydrogen polarizer yielded a polarization of 0.013%. The nuclear-spin polarizations achieved in these experiments are the first reported to date involving heterogeneous reactions in water.

NMR offers many possibilitiesi nc hemical analysis, structurali nvestigations, and medical diagnostics. Although it is broadly used, one of NMR spectroscopies main drawbacks is low sensitivity.H yperpolarization techniques enhanceN MR signals by more than four orders of magnitude allowing the design of new contrast agents. Parahydrogen induced polarization that utilizes the parahydrogen's singlet state to create enhanced signals is of particular interests ince it allows to producem olecular imagingagentswithin seconds. Herein,wepresent astrategy for signal enhancement of the carbonyl 13 Ci na mino acids by using parahydrogen,a sd emonstratedf or glycine and alanine. Importantly,t he hyperpolarizations tep is carried out in water and chemically unmodifiedc anonical amino acids are obtained. Our approach thus offers ah igh degree of biocompatibility,w hich is crucial for furthera pplication. The rapid sample hyperpolarization (withins econds) may enable the continuous productiono fb iologically useful probes, such as metabolic contrast agents or probes for structuralbiology.[e] Prof. Dr.M.U tz SchoolofC hemistry,University of Southampton SouthamptonS O171BJ (UK)Supporting information and the ORCID identification number(s) for the author(s) of this articlecan be found under: https://doi.

Hyperpolarization techniques are key to extending the capabilities of MRI for the investigation of structural, functional and metabolic processes in vivo. Recent heterogeneous catalyst development has produced high polarization in water using parahydrogen with biologically relevant contrast agents. A heterogeneous ligand-stabilized Rh catalyst is introduced that is capable of achieving N polarization of 12.2±2.7 % by hydrogenation of neurine into a choline derivative. This is the highest N polarization of any parahydrogen method in water to date. Notably, this was performed using a deuterated quaternary amine with an exceptionally long spin-lattice relaxation time (T ) of 21.0±0.4 min. These results open the door to the possibility of N in vivo imaging using nontoxic similar model systems because of the biocompatibility of the production media and the stability of the heterogeneous catalyst using parahydrogen-induced polarization (PHIP) as the hyperpolarization method.

Platinum nanoparticles capped with cysteine ligands were synthesized and utilized to create the highest polarization reported to date for heterogeneous PHIP in water.