The Effect of Gadolinium Doping in [ 13 C 6 , 2 H 7 ]Glucose Formulations on 13 C Dynamic Nuclear Polarization at 3.35 T

The promise of hyperpolarized glucose as a non-radioactive imaging agent capable of reporting on multiple metabolic routes has led to recent advances in its dissolution-DNP (dDNP) driven polarization using UV-light induced radicals and trityl radicals at high field (6.7 T) and 1.1 K. However, most preclinical dDNP polarizers operate at the field of 3.35 T and 1.4-1.5 K. Minute amounts of Gd complexes have shown large improvements in solid-state polarization, which can be translated to improved hyperpolarization in solution. However, this Gd effect seems to depend on magnetic field strength, metal ion concentration, and sample formulation. The effect of varying Gd concentrations at 3.35 T has been described for C-labeled pyruvic acid and acetate. However, it has not been studied for other compounds at this field. The results presented here suggest that Gd doping can lead to various concentration and temperature dependent effects on the polarization of [ C , H ]glucose, not necessarily similar to the effects observed in pyruvic acid or acetate in size or direction. The maximal polarization for [ C , H ]glucose appears to be at a Gd concentration of 2 mM, when irradiating for more than 2 h at the negative maximum of the DNP intensity profile. Surprisingly, for shorter irradiation times, higher polarization levels were determined at 1.50 K compared to 1.45 K, at a [Gd ]=1.3 mM. This was explained by the build-up time constant and maximum at these temperatures.