Physics

Organic chemistry

Combinatorial chemistry

Hydrogen

Nuclear magnetic resonance spectroscopy

Stereochemistry

Biology

Hyperpolarization (physics)

Catalysis

Physical chemistry

Spin isomers of hydrogen

Chemistry

Ecology

Polarization (electrochemistry)

Substrate (aquarium)

Molecule

Quantum mechanics

Electrical resistivity and conductivity

Induced polarization

Magnetic Resonance Materials in Physics Biology and Medicine

ParaHydrogen induced polarization (PHIP) is an efficient and cost-effective hyperpolarization method, but its application to biological investigations has been hampered, so far, due to chemical challenges. PHIP is obtained by means of the addition of hydrogen, enriched in the para-spin isomer, to an unsaturated substrate. Both hydrogen atoms must be transferred to the same substrate, in a pairwise manner, by a suitable hydrogenation catalyst; therefore, a de-hydrogenated precursor of the target molecule is necessary. This has strongly limited the number of parahydrogen polarized substrates. The non-hydrogenative approach brilliantly circumvents this central issue, but has not been translated to in-vivo yet. Recent advancements in hydrogenative PHIP (h-PHIP) considerably widened the possibility to hyperpolarize metabolites and, in this review, we will focus on substrates that have been obtained by means of this method and used in vivo. Attention will also be paid to the requirements that must be met and on the issues that have still to be tackled to obtain further improvements and to push PHIP substrates in biological applications.

Hydrogenative-PHIP polarized metabolites for biological studies