Efficient Parahydrogen-Induced 13 C Hyperpolarization on a Microfluidic Device

We show the direct production and detection of $^{13}$C-hyperpolarized fumarate by parahydrogen-induced polarization (PHIP) in a microfluidic lab-on-a-chip (LoC) device and achieve 8.5% $^{13}$C polarization. This is the first demonstration of $^{13}$C-hyperpolarization of a metabolite by PHIP in a microfluidic device. LoC technology allows the culture of mammalian cells in a highly controlled environment, providing an important tool for the life sciences. In-situ preparation of hyperpolarized metabolites greatly enhances the ability to quantify metabolic processes in such systems by microfluidic NMR. PHIP of 1H nuclei has been successfully implemented in microfluidic systems, with mass sensitivities in the range of pmol/s. However, metabolic NMR requires high-yield production of hyperpolarized metabolites with longer spin life times than is possible with 1H. This can be achieved by transfer of the polarization onto $^{13}$C nuclei, which exhibit much longer T$_1$ relaxation times. We report an improved microfluidic PHIP device, optimized using a finite element model, that enables the direct and efficient production of $^{13}$C-hyperpolarized fumarate.