University of Twente Student Theses


Development of a microfluidic device for point of care testing of oxidative stress

Hammink, E.J. (2022) Development of a microfluidic device for point of care testing of oxidative stress.

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Embargo date:13 July 2024
Abstract:Introduction: Oxidative stress, an imbalance between the generation of oxidants and the availability of anti-oxidants, is associated with multiple pathological conditions. Plasma free thiol levels reliably reflect the redox status, as the sulfhydryl group (R-SH) is readily oxidized by oxidants. Multiple studies have shown the potential of plasma free thiol levels as biomarker in various conditions, such as inflammatory bowel disease. Current detection of free thiols is time-consuming and laborious. In these thesis, first steps were taken towards the development of a microfluidic device for point-of-care detection of free thiols using finger-prick blood. Materials & Methods: The standard protocol for free thiol detection with 5,5-dithio-bis-2[2-nitrobenzoic acid] (DTNB) described by Ellman was adjusted and applied to lower plasma samples. A polymethylmethacrylate (PMMA) master mould was fabricated using micro milling for the replication of polydimethylsiloxane (PDMS) microfluidic devices, in which absorbance measurements were performed. Trigger valves with different geometries were designed and tested. These trigger valves were combined with passive micromixer structures to enable on-chip mixing of DTNB and diluted plasma. Results: Free thiol measurements of 6 µL plasma resulted in an average inter-coefficient of variation (CV) below 5% and an intra-CV below 11% (n=8). On-chip absorbance measurements resulted in an intra-CV below 4% (n=6). The determined concentrations were comparable to the values obtained with the standard protocol. Trigger valves were able to temporarily stop (at least 10 minutes) fluid flow using a pressure barrier. The current design of the mixing component does not noticeably increase mixing efficiency and needs optimization. Conclusion: Our results show the promising potential of microfluidic devices for the rapid determination of free thiols in small volume plasma samples. To achieve point-of-care testing, further sample preparation steps need to be integrated on the microfluidic device such as plasma separation and dilution.
Item Type:Essay (Master)
Faculty:TNW: Science and Technology
Subject:42 biology, 44 medicine
Programme:Biomedical Engineering MSc (66226)
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