Efficient Parahydrogen Induced 13C Hyperpolarization on a Microfluidic Device

Abstract

In this work we demonstrate the direct production and detection of carbon-hyperpolarized fumarate by parahydrogen-induced polarization (PHIP) in a microfluidic Lab-on-a-Chip (LoC) device and achieve 8.5% 13C polarization. This is the first demonstration of 13C-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 but only with low yields. Metabolic NMR requires high-yield production of hyperpolarized metabolites with longer spin life times than is possible with1H. This can be achieved by transfer of the polarization onto 13C nuclei, which exhibit much longer T1 relaxation times. We report an improved microfluidic PHIP device that has been optimised using a finite element model that achieves a more than 20-fold improvement in the yield of the hyperpolarized product. It is shown that this enables detailed kinetic studies of the hydrogenation of propargyl acetate to allyl acetate, as well as the direct production of 13C hyperpolarized fumarate.