SLIC-SABRE at Microtesla Fields Enables High Levels of Nuclear Spin Polarization Without Magnetic Shielding

Employing nuclear spin hyperpolarization to enhance NMR sensitivity opens new horizons for metabolic studies and chemical reaction monitoring. Among the hyperpolarization techniques, Signal Amplification by Reversible Exchange (SABRE) is prominent for its ability to transfer spin order from parahydrogen to target nuclei, especially ¹³C and ¹⁵N, without the chemical modification of the substrate under study. Despite its power, existing implementations of SABRE require expensive equipment like radiofrequency (RF) hardware and magnetic shielding. This paper demonstrates the SLIC-SABRE (Spin Lock Induced Crossing SABRE) method at low magnetic fields as a low-cost and efficient technique for achieving high ¹⁵N polarization using a simple setup, consisting only of a small set of magnetic coils driven by a desktop PC sound card. The method yields from 5 up to 17 % polarization across various SABRE-active molecules, outperforming the conventional SABRE-SHEATH (SABRE in SHield Enables Alignment Transfer to Heteronuclei) approach and significantly enhancing the accessibility of hyperpolarization techniques.