A droplet microfluidic redox sensor

Abstract

Total free thiols are an important marker of the body’s redox state, which have shown correlations with disease severity and recovery in numerous conditions including COVID-19, sepsis and in renal transplant patients. Recent research has highlighted that increased insight may be gained by taking regular measurements to monitor trends in redox stressors such as disease, exercise, and hypoxia. However, conducting such studies is currently challenging due to the requirement for repeated venous blood sampling and intensive lab work. Droplet microfuidic sensors offer a platform for developing a point of care testing approach, using small sample volumes and automated systems to replicate laboratory testing. In this thesis, I had developed a small, portable droplet microfuidic sensor that can measure total free thiols in plasma, providing the reading in less than 10 minutes. This system used a novel method to introduce bumps into a PTFE fow channel to enhance the mixing of droplets containing complex biological fuids. The results in a range of real plasma samples showed equivalence with current standard laboratory assay, while reducing sample volume requirements nine-fold from 90 µl to 10 µl and fully automating the process. Integrated, membrane-based, plasma separation was developed, providing high-purity plasma from whole blood input. However, an immune response of platelets and white blood cells on contact with the membrane resulted in signifcant interference when measuring total free thiols in the output. An alternative capillary centrifuging strategy allowed testing of capillary blood samples collected by fngerprick lancing. The system was used to monitor total free thiols using fngerprick samples in healthy volunteers and revealed signifcant changes in total free thiols in response to food intake and exercise. This device will improve our ability to conduct physiological studies investigating total free thiols which could improve our understanding of redox physiology, which may ultimately improve medical care.

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Identifiers

ORCID for Adrian Nightingale: orcid.org/0000-0003-2445-4827

ORCID for Martin Feelisch: orcid.org/0000-0003-2320-1158

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