Parahydrogen-Induced Hyperpolarisation 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.