Effect of ionic interaction between a hyperpolarized magnetic resonance chemical probe and a gadolinium contrast agent for the hyperpolarized lifetime after dissolution

In hyperpolarization of ¹³C-enriched magnetic resonance chemical probes in the solid-state, a trace amount of gadolinium (Gd) contrast agent can be used to maximize polarization of the ¹³C nuclear spins. Here, we report systematic measurement of the spin-lattice relaxation time (T₁) and enhancement level of ¹³C-enriched chemical probes in the presence of various Gd contrast agents in the liquid-state after dissolution. Using two different ¹³C probes having opposite electric charges at neutral pH, we clearly show the T₁ of hyperpolarized ¹³C was barely affected by the use of a Gd complex that displays repulsive interaction with the ¹³C probe in solution, whilst T₁ was drastically shortened when there was ionic attraction between probe and complex.