paraQchip - Parahydrogen-Induced Hyperpolarisation On A Chip For Microfluidic Perfusion Culture

Nuclear magnetic resonance (NMR) is one of the most powerful tools for investigating the structure, composition, and dynamics of living and non-living matter. Its sensitivity is limited by the degree of alignment of nuclear spins, which is small even in the strongest magnets. Hyperpolarisation techniques such as parahydrogen-induced polarisation can produce much better spin alignments, offering corresponding increases in sensitivity. paraQchip aims provide lab-on-a-chip (LoC) cultures of cells with hyperpolarised metabolites (pyruvate, fumarate) for high-sensitivity NMR monitoring of metabolism, by integrating all steps of parahydrogen-induced polarisation (PHIP) onto the chip. To this end, we propose an interdisciplinary research programme that uses quantitative modelling of spin dynamics, transport, and kinetic processes in tandem with experimental quantification of reaction and transport kinetics to inform the design of the microfluidic chip layout, NMR detector, radiofrequency pulse sequences, and operation parameters such as flow rates, reagent concentrations, solvents, and temperature. The main challenge lies in the concerted operation of the hydrogenation, polarisation transfer, and purification steps, which must all be completed before nuclear relaxation destroys the hyperpolarisation. The proposed research consists of four work packages, each led by one of the Co-PIs. WP 1 (Kuprov) focusses on modelling, using a novel approach that treats spin and spatial degrees of freedom on an equal footing. WP 2 (Levitt) deals with the required transfer of polarisation from the parahydrogen spin order to the target metabolite. This requires design of a novel microfluidic NMR probe system with separate detectors for the transfer step and for downstream observation. WP 3 (Whitby) will focus on the chemical aspects, including hydrogenation, cleavage, and purification. Finally, WP 4 (Utz) deals with the microfluidic integration of these steps. LoC devices provide detailed control over the growth conditions of cells, tissues (organ-on-a-chip), and small organisms, providing valuable models supporting the development of diagnostics and therapies, and drug safety testing. NMR spectroscopy could be of great use in this context, as it allows non-invasive quantification of metabolic processes. However, the limited sensitivity of conventional NMR is exacerbated at the microlitre volume scale of LoC devices. paraQchip will address that, pushing the limit of detection from the millimolar concentration range down to micromolar. This will allow detailed in-situ observation of metabolic processes in microfluidic cell cultures as well as tissue and organ models, with many applications in disease modelling, drug testing, and other aspects of the life sciences. Microfluidic implementation of PHIP will also lead to deeper understanding of the interplay between the hydrogenation reaction mechanism and nuclear spin relaxation processes. The computational tools developed and validated through paraQchip will benefit the development of hyperpolarised magnetic resonance imaging techniques.