Staff member

Organ-on-chip (OoC) systems are advancing rapidly as physiologically relevant in vitro models. However, real-time, noninvasive metabolic monitoring tools remain lacking. While NMR offers a powerful solution, current setups are not compatible with the planar format of microfluidic chips. Here we introduce the first benchtop NMR spectrometer for real-time metabolic monitoring of cell cultures on microfluidic platforms, utilizing hyperpolarization via dissolution dynamic nuclear polarization. This work details modifications made to a commercial benchtop NMR spectrometer, including the design and fabrication of a microfluidic platform that enables precise injection of hyperpolarized substrates and continuous renewal of cell culture media. The platform integrates a radiofrequency coil for signal transmission and reception and incorporates a custom-built sample carrier. Preliminary NMR data acquired with this system demonstrate its feasibility for dynamic metabolic studies.

JTD Keywords: Cancer, Pyruvate

The sensitivity of NMR may be enhanced by more than four orders of magnitude via dissolution dynamic nuclear polarization (dDNP), potentially allowing real-time, in situ analysis of chemical reactions. However, there has been no widespread use of the technique for this application and the major limitation has been the low experimental throughput caused by the time-consuming polarization build-up process at cryogenic temperatures and fast decay of the hyper-intense signal post dissolution. To overcome this limitation, we have developed a microfluidic device compatible with dDNP-MR spectroscopic imaging methods for detection of reactants and products in chemical reactions in which up to 8 reactions can be measured simultaneously using a single dDNP sample. Multiple MR spectroscopic data sets can be generated under the same exact conditions of hyperpolarized solute polarization, concentration, pH, and temperature. A proof-of-concept for the technology is demonstrated by identifying the reactants in the decarboxylation of pyruvate via hydrogen peroxide (e.g. 2-hydroperoxy-2-hydroxypropanoate, peroxymonocarbonate and CO2). dDNP-MR allows tracing of fast chemical reactions that would be barely detectable at thermal equilibrium by MR. We envisage that dDNP-MR spectroscopic imaging combined with microfluidics will provide a new high-throughput method for dDNP enhanced MR analysis of multiple components in chemical reactions and for non-destructive in situ metabolic analysis of hyperpolarized substrates in biological samples for laboratory and preclinical research.

JTD Keywords: injections, nmr, pyruvate, Polarization