Hyperpolarized [1-13C]-L-Lactate Production

Sodium [1-¹³C]-L-lactate was purchased from Cambridge Isotope Laboratories, Inc. (Tewksbury MA, USA). 2.1-M [1-¹³C]-L-lactate was prepared in 4:1 w/w water:glycerol with 15-mM OX063 as previously described(15 (link), 16 (link)). A SPINlab™ polarizer (GE Healthcare, Waukesha WI, USA) that operates at 5T and ~0.8 K was used for polarizing [1-¹³C]-L-lactate. 90 or 180 μL of the lactate sample was placed in a sample vial and assembled with a research fluid path (GE Healthcare), which included 16 mL of dissolution media containing 0.1 g/L of disodium ethylenediaminetetraacetate (Na₂EDTA). The sample was dissolved after approximately 5 hours of polarization, yielding ~6.0 mL of 30- or 60-mM hyperpolarized [1-¹³C]-L-lactate. Liquid polarization level and longitudinal relaxation time (T₁) of hyperpolarized [1-¹³C]-L-lactate were calculated from independent in vitro measurements as described in the Supporting Information.