Effect of the hydrogenation solvent in the PHIP-SAH hyperpolarization of [1- 13 C]pyruvate

TL;DR

This study investigates how different solvents affect the efficiency and hyperpolarization level in the PHIP-SAH method for producing hyperpolarized pyruvate, aiming to optimize biocompatible solutions for in-vivo diagnostics.

Contribution

It demonstrates that solvent choice significantly impacts hydrogenation efficiency and hyperpolarization, and introduces a phase extraction method to improve biocompatibility of the hyperpolarized product.

Findings

Coordinating solvents increase hyperpolarization but are not biocompatible.

Hydrogenation in chloroform and toluene allows phase extraction.

Filtration removes organic traces, enhancing biocompatibility.

Abstract

ParaHydrogen Induced Polarization-Side Arm Hydrogenation (PHIP-SAH) is an inexpensive tool to obtain hyperpolarized pyruvate (and other metabolites) that can be applied to in-vivo diagnostics, for the investigation of metabolic processes. This method is based on hydrogenation, using hydrogen enriched in the para-isomer, of unsaturated substrates, catalyzed, usually, by a homogeneous rhodium(I) complex. In this work, the effect of the solvent on the hydrogenation efficiency and on the hyperpolarization level were investigated. Coordinating solvents, such as acetone and methanol, can increase significantly either the efficiency or the hyperpolarization level, but they are not compatible with the intended metabolic applications. The phase extraction of the hyperpolarized product (sodium pyruvate) in an aqueous solution was obtained carrying out the hydrogenation reaction in chloroform and toluene. The traces of the organic solvents in the water phase were removed, by means of filtration through a lipophilic resin, thus improving the biocompatibility of the aqueous solution of the hyperpolarized product.