Hyperpolarized 13C MRS of Pyruvate Metabolism

MRS was performed at 37°C on a Bruker 11.7 T spectrometer. Hyperpolarized ¹³C in vitro: 18 mg [1-¹³C]pyruvic acid (99% isotopically enriched, Sigma-Aldrich, UK containing 15 mM trityl free radical OX63, Oxford Instruments, UK) was polarized in a HyperSense® DNP polarizer (Oxford Instruments Molecular Biotools Ltd, UK) for 1 hour. The polarized sample was dissolved in 4 ml aqueous buffer (50 mM sodium lactate, 50 mM NaOH, 1 mM EDTA) resulting in a 50 mM pyruvate solution at pH 7, 37°C. A solution of 100 µl, 50 mM hyperpolarized [1-¹³C]pyruvate was mixed with 500 µl cell suspension, and ¹³C spectra were acquired every 2 s using a single scan and a 10° flip angle.