High-resolution microtesla in-situ¹³C NMR detection of "scaled-up" SABRE-hyperpolarization of [1-¹³C]pyruvate

SABRE-SHEATH (Signal Amplification by Reversible Exchange in SHield Enables Alignment Transfer to Heteronuclei) is a parahydrogen-based hyperpolarization technique increasingly used for metabolic sensing. Typically limited to 5-mm NMR tube reactors (0.5-1 mL volumes) and requiring manual sample transfer for quantification, SABRE remains constrained by its throughput. Here, we describe a new low-field magnetic resonance system that enables in-situ polarimetry of hyperpolarized [1-¹³C]pyruvate. This setup utilizes a mu-metal shielded solenoid magnet, performing hyperpolarization at 0.4 μT (SABRE-SHEATH) and in-situ NMR sensing at 140 μT (1.6 kHz ¹³C frequency), which eliminates the need for sample transfer. We demonstrate that a surface-coil detection design accommodates diverse sample geometries, including 15-mm ID HPLC columns. By increasing the parahydrogen flow rate 12-fold, we successfully scaled the production of [1-¹³C]pyruvate to a 10-mL volume, achieving a 7% polarization level-comparable to that of smaller 0.8-mL samples. Furthermore, the integration of automated fluidics and a saddle-shaped RF excitation coil enables both SABRE-SHEATH and Spin-Lock Induced Crossing (SLIC)-SABRE protocols. Notably, we demonstrate the utility of this in-situ detection for optimizing SABRE conditions, including the screening of DMSO concentrations. Finally, the ability to operate with diverse solvent systems and scalable volumes lays the foundation for producing biocompatible hyperpolarized formulations, broadening the potential for metabolic research. These advances establish a scalable, automated framework for producing larger, biocompatible volumes of hyperpolarized molecular probes.