Monitoring Oxygen Levels in Microfluidic Devices using 19F NMR
Sylwia Ostrowska (1)*, Bishnubrata Patra (1), Ciara Nelder (1), Manvendra Sharma (1), Marcel Utz (2)
- University of Southampton, 2. School of Chemistry, University of Southampton
We report an in-situ, non-invasive approach to quantify oxygen partial pressure in microfluidic lab-on-a-chip (LoC) devices. LoC systems provide a versatile platform to culture biological systems. As they allow a detailed control over the growth conditions, LoC devices are finding increasing applications in the culture of cells, tissues and other biological systems
. Integrated microfluidic NMR spectroscopy  allows non-invasive monitoring of metabolic processes in such systems. Quantification of oxygen partial pressure would help ensuring stable growth conditions, and provide a convenient means to assess the viability of the cultured system. However, oxygen, one of the most important metabolites, cannot be quantified using either proton or carbon NMR spectroscopy. As is well known, the oxygen partial pressure can be determined by MRI in vivo by measuring the 19F spin-lattice relaxation time of perfluorinated agents . Here, we show that the oxygen partial pressure in microfludic devices of 2.5 μl can be quantified using the 19F spin-lattice relaxation rate of perfluorinated tributylamine. The compound is added to the aquous perfusion medium in the form of micrometer-sized droplets. Our set up comprises a microfluidic device and a PDMS layer sandwiched between two 3D printed holders. The droplet emulsion is delivered via a syringe pump and carbogen is delivered through a separate channel. The semi- permeable PDMS layer acts as a diffusion bridge between the liquid and gas channels, allowing for oxygen to diffuse into the emulsion. T1 is obtained through standard inversion recovery experiments detected using a home-built transmission-line probe. Due to the non-toxic nature of droplet emulsion, it can be easily incorporated into the perfusion fluid allowing for quantification of tissue oxygen levels.
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