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Cell Metabolomics on A Chip By Integrated High-Resolution NMR Spectroscopy

Final Report Summary - UF-NMR (Cell Metabolomics on A Chip By Integrated High-Resolution NMR Spectroscopy)

The overarching aim of the uF-NMR project was the successful integration of Dr. Marcel Utz into the European research environment, and specifically into the Chemistry Department at the University of Southampton. Dr. Utz was recruited from a position as Associate Professor of Mechanical and Aerospace Engineering, with a minor appointment in Chemistry, at the University of Virginia in 2012. He was initially hired at the level of Reader. In 2014, partially with the support of uF-NMR, he was promoted to full Professor at the University of Southampton (with a personal chair in Magnetic Resonance). He has since then been promoted to Head of the magnetic resonance research section and the faculty NMR research facility, and is thus part of the senior management of the Department of Chemistry. He has established multiple research cooperations within the University of Southampton, including with the groups of Prof. M. Levitt (Chemistry), H. Ulbricht (Physics), Prof. S. Khakoo (Hepatology), as well as with Dr. J. Werner (Biological Sciences). In addition, his research group has established strong ties with the University of Groningen and the Karlsruhe Institute of Technology through the H2020 FETOpen project TISuMR, which Prof. Utz is coordinating. TISuMR was the first successful FETOPEN bid from the University of Southampton. Prof. Utz has been invited as guest speaker at several scientific meetings in the UK, and is regularly called upon as external referee for PhD exams. It is therefore fair to say that Prof. Utz is now firmly established in the scientific and academic communities in Europe.
On the scientific side, the uF-NMR project was focused on integrating microfluidc lab-on-a-chip devices with nuclear magnetic resonance (NMR) spectroscopy. Microfluidic devices implement complex biological or chemical experiments at small scale, replacing conventional handling of liquids with a micro-fabricated network of channels and valves. They are increasingly used in the life sciences to culture cells, tissues, and small organisms. uF-NMR was aimed at combining this technology with the analytical power of NMR spectroscopy, which can provide detailed information on metabolic processes from living tissues and cells without disturbing them.
To succeed in this, a novel type of NMR detectors needed to be developed and optimised which can accommodate microfluidic lab-on-a-chip devices. This was accomplished by replacing the usual receiver coil with a planar transmission line resonator, into which a microfluidic device can be inserted. Through careful optimisation of the geometry, this design achieves among the highest NMR sensitivities for its sample size (about 1 µl). It has been demonstrated that metabolic processes in a microfluidic cell culture can be followed over a period of several hours.
The combination of NMR and microfluidic systems is challenging not only due to the small sample size and the high sensitivity therefore required. The processes and materials that have been established for microfluidic devices are not all compatible with the stringent requirements of NMR spectroscopy. For example, the spectral resolution of NMR depends on extremely homogeneous magnetic fields over the entire sample volume. Differences in magnetic properties between the device material (usually a polymer or glass) and the sample fluid tend to deteriorate this homogeneity. As part of uF-NMR a novel concept to manage such disparities, called “structural shimming”, has been developed and successfully demonstrated. This has even been extended to allow high-resolution NMR spectroscopy in droplet-based microfluidic systems, which use an inert oil phase to transport small droplets of water-based samples through the fluidic network.
Another specific aim of uF-NMR was to explore using nuclear magnetic hyper-polarisation techniques in microfluidic systems. Under normal circumstances, the nuclear magnetic polarisation that gives rise to the NMR signal is minuscule, even at the largest practical magnetic fields. Under special circumstances, it can be increased to almost perfect alignment of nuclear spins, giving several orders of magnitude higher sensitivity. In the context of microfluidic cultures, this would allow to follow chemical processes at very low concentrations, such as signalling interactions between cells. Significant progress towards this goal has been made as part of uF-NMR. An important class of hyperpolarisation methods relies on the long-lived spin order of para-hydrogen gas. The Utz group are developing a novel microfluidic approach towards handling para-hydrogen induced polarisation in microfluidic devices. While work in this area is still ongoing, a new chip design has been developed for this purpose, and the life time of para-hydrogen spin order in gas-permeable silicone rubber membranes has been measured. Conclusive results are expected over the next few months.
Another exciting outcome is the demonstration of nuclear double resonance experiments. This enables the simultaneous excitation of both proton and carbon nuclear precession. Double- and triple resonance techniques are at the heart of protein NMR spectroscopy, which enables the study of protein structure and dynamics in solution. On this basis, we have succeeded in acquiring fully resolved correlation spectra of a microfluidic sample of ubiquitin, with all residues clearly resolved.
In summary, the results from uF-NMR have proven the usefulness of NMR spectroscopy in the context of microfluidic lab-on-a-chip devices. The goal of monitoring metabolic processes in a on-chip cell culture has been achieved, and important steps towards hyper polarised NMR on a chip have been taken.
These results open interesting avenues for future impact in the life sciences, where microfluidic culture devices are increasingly used as disease models for drug discovery and testing, as scaffolds for tissue engineering, and as an alternative to vivisection for drug safety testing. They also hold promise for the study of proteins that are only available in small quantities due to difficult expression.