Optimisation of pyruvate hyperpolarisation using SABRE by tuning the active magnetisation transfer catalyst

Area of Science:

• Nuclear Magnetic Resonance (NMR) spectroscopy
• Hyperpolarisation techniques
• Medical Imaging

Background:

• Signal amplification by reversible exchange (SABRE) significantly amplifies NMR signals compared to Boltzmann conditions.
• SABRE utilizes para-hydrogen and iridium complexes to transfer magnetization to substrates.
• Pyruvate is a key substrate for in vivo MRI studies, and its hyperpolarisation is crucial for enhanced imaging.

Purpose of the Study:

• To optimize pyruvate-13C2 signal gains achieved through SABRE hyperpolarisation.
• To investigate the impact of varying carbene and sulfoxide ligands on the iridium catalyst.
• To establish a rationale for achieving high, cost-effective, and refreshable pyruvate signal enhancements.

Main Methods:

• Systematic variation of carbene and sulfoxide ligands in the iridium catalyst.
• Detailed study of the formation and behavior of the active [Ir(H)2(η2-pyruvate)(sulfoxide)(NHC)] catalyst.
• Evaluation of hyperpolarisation efficiency and signal enhancement for pyruvate-13C2.

Main Results:

• Achieved signal enhancements of 2140-fold for the 1-13C site and 2125-fold for the 2-13C site of sodium pyruvate-1,2-[13C2].
• Demonstrated the significant influence of ligand properties on catalyst performance and signal gain.
• Developed a method for achieving substantial signal enhancements in a cost-effective and refreshable manner.

Conclusions:

• Ligand tuning of the iridium catalyst is critical for maximizing SABRE hyperpolarisation efficiency in pyruvate.
• The optimized SABRE approach offers a promising method for enhancing pyruvate signals in MRI.
• This work provides a foundation for developing more efficient hyperpolarisation strategies for metabolic imaging.