Portable Cavity Enhanced Absorption Measurement of Sepsis Biomarkers

Abstract

Recent advances in the understanding of sepsis suggest that the life-threatening organ dysfunction that is responsible for up to 11 million sepsis-related deaths each year is due to a combination of an inappropriately aggressive immune response and an opposing state of immunosuppression in response to a foreign pathogen. A plethora of biomarkers have been touted as potential sepsis biomarkers. Despite the wealth of recent research, no single biomarker has yet been identified that has sufficient diagnostic power to enable the diagnosis of sepsis, and as such this remains a significant clinical challenge. Combining a panel of biomarkers may provide more diagnostic power, along with the use of point-of-care testing to enable faster result turnaround times, which is especially desirable as the delay in sepsis diagnosis and initiation of treatment is associated with an increase in morbidity and mortality. C-reactive protein (CRP), Procalcitonin (PCT) and Interleukin-6 (IL-6) were identified as candidate sepsis biomarkers due to the significant amount of research into their potential to aid the diagnosis of sepsis. Analysis of these is possible using a variety of methods, including enzyme-linked immunoabsorbance assay (ELISA). The aim of these experiments was to develop an ELISA for each biomarker and to combine these with cavity enhanced absorption measurements using a novel portable cavity enhanced absorption reader. This technique utilises an optical cavity around the sample, effectively increasing the light path length through the sample and therefore increasing measurement sensitivity. An ELISA for CRP was initially set up using a polystyrene matrix with microplate reader measurement, which demonstrated good comparability to the Siemens CRP assay. This was modified with the introduction of a glass matrix, enabling measurements to be made using the portable reader instrument, with results comparable to the Siemens CRP assay. PCT and IL-6 ELISAs were subsequently set up, with the feasibility of PCT and IL-6 measurements demonstrated with the portable reader. Comparison of the portable reader with two different microplate readers indicated that the portable reader is able to make more sensitive measurements, estimated to be 14 times more sensitive than those achievable with either microplate reader. The feasibility of sepsis biomarker measurements with cavity enhanced absorption using a portable instrument has for the first time been demonstrated, which could be used for point-of-care testing and could be further applied to the measurement of other protein biomarkers.

Date of Award	1 Aug 2021
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Paul Dark (Supervisor)