Electrochemical biosensors for continuous infection monitoring and early detection of sepsis
File(s)
Author(s)
Jangam, Saylee
Type
Thesis
Abstract
The aim of this thesis was to develop electrochemical biosensors for the purpose of continuous infection monitoring. Lactate and C-reactive protein (CRP) were chosen as the biomarkers of interest to (i) detect early-warning signs of sepsis and (ii) monitor infection levels to support dose optimisation of antimicrobials, respectively.
A first-generation microneedle-based lactate oxidase biosensor was developed, and its dynamic range was extended using polyelectrolyte membranes. Koutecký–Levich analysis of the mass transport of lactate in the membranes revealed that polyurethane, cellulose acetate and Nafion performed best in extending the dynamic range. Nafion was chosen as the membrane for in vivo studies conducted with healthy volunteers producing lactate during exercise due to ease of fabrication methods and relatively high dynamic range. The in vivo studies showed good agreement between ISF (biosensor) and blood lactate, as well as between ISF and dialysate lactate (via microdialysis).
An electrochemical aptamer biosensor (E-AB) was developed for CRP using an aptamer reported by Huang et al. The aptamer was modified with a methylene blue redox reporter and optimised with respect to signal response. The aptamer was successfully deposited on the electrode, however, an electrochemical signal difference was not seen between bound and unbound states using multiple modalities. The same aptamer was modified with an osmium(II/III) redox label, developed by Ben Aissa et al., and E-ABs fabricated. The aptamer was successfully deposited on the electrodes and able to produce a signal response at a potential of +0.2 V, however, there was some overlap with background signals.
A first-generation microneedle-based lactate oxidase biosensor was developed, and its dynamic range was extended using polyelectrolyte membranes. Koutecký–Levich analysis of the mass transport of lactate in the membranes revealed that polyurethane, cellulose acetate and Nafion performed best in extending the dynamic range. Nafion was chosen as the membrane for in vivo studies conducted with healthy volunteers producing lactate during exercise due to ease of fabrication methods and relatively high dynamic range. The in vivo studies showed good agreement between ISF (biosensor) and blood lactate, as well as between ISF and dialysate lactate (via microdialysis).
An electrochemical aptamer biosensor (E-AB) was developed for CRP using an aptamer reported by Huang et al. The aptamer was modified with a methylene blue redox reporter and optimised with respect to signal response. The aptamer was successfully deposited on the electrode, however, an electrochemical signal difference was not seen between bound and unbound states using multiple modalities. The same aptamer was modified with an osmium(II/III) redox label, developed by Ben Aissa et al., and E-ABs fabricated. The aptamer was successfully deposited on the electrodes and able to produce a signal response at a potential of +0.2 V, however, there was some overlap with background signals.
Version
Open Access
Date Issued
2024-01
Date Awarded
2024-07
Copyright Statement
Creative Commons Attribution NonCommercial Licence
License URL
Advisor
O'Hare, Danny
Publisher Department
Bioengineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)