LIGHT-SABRE Hyperpolarizes 1-13C-Pyruvate Continuously without Magnetic Field Cycling

J Phys Chem C Nanomater Interfaces. 2023 Apr 4;127(14):6744-6753. doi: 10.1021/acs.jpcc.3c01128. eCollection 2023 Apr 13.


Nuclear spin hyperpolarization enables real-time observation of metabolism and intermolecular interactions in vivo. 1-13C-pyruvate is the leading hyperpolarized tracer currently under evaluation in several clinical trials as a promising molecular imaging agent. Still, the quest for a simple, fast, and efficient hyperpolarization technique is ongoing. Here, we describe that continuous, weak irradiation in the audio-frequency range of the 13C spin at the 121 μT magnetic field (approximately twice Earth’s field) enables spin order transfer from parahydrogen to 13C magnetization of 1-13C-pyruvate. These so-called LIGHT-SABRE pulses couple nuclear spin states of parahydrogen and pyruvate via the J-coupling network of reversibly exchanging Ir-complexes. Using ∼100% parahydrogen at ambient pressure, we polarized 51 mM 1-13C-pyruvate in the presence of 5.1 mM Ir-complex continuously and repeatedly to a polarization of 1.1% averaged over free and catalyst-bound pyruvate. The experiments were conducted at -8 °C, where almost exclusively bound pyruvate was observed, corresponding to an estimated 11% polarization on bound pyruvate. The obtained hyperpolarization levels closely match those obtained via SABRE-SHEATH under otherwise identical conditions. The creation of three different types of spin orders was observed: transverse 13C magnetization along the applied magnetic field, 13C z-magnetization along the main field B 0, and 13C-1H zz-spin order. With a superconducting quantum interference device (SQUID) for detection, we found that the generated spin orders result from 1H-13C J-coupling interactions, which are not visible even with our narrow linewidth below 0.3 Hz and at -8 °C.

PMID:37081994 | PMC:PMC10108362 | DOI:10.1021/acs.jpcc.3c01128


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