Development of non-esterified fatty acid (NEFA) electrochemical biosensor for energy metabolism studies

PhD ThesisThere are many energy metabolism studies ongoing, including those for cardiovascular diseases and type-2-diabetes. With an increase in people being diagnosed with type-2-diabetes, there should be more ways to monitor not only the blood glucose levels but also the other biomarkers associated with type-2-diabetes. The metabolism biomarkers are essential in understanding the cause of diabetes early on. These biomarkers include: glucose, non-esterified fatty acid, lactate, urea, creatinine, glycosylated haemoglobin and cholesterol. Whilst glucose measurement has a clear role in type-2-diabetes management, the potential value of non-esterified fatty acid has not been explored or highlighted yet. The aim of this project is to develop an electrochemical biosensor for the non-esterified fatty acid in human blood, as non-esterified fatty acid can cause -cell loss in type-2-diabetes. Exploration of this biomarker would be a step forward in increasing research and patient understanding of the dynamic processes involved in establishing good metabolism control. The project uses the enzymes in commercial optical methods for non-esterified fatty acid detection. Oleic acid was used as the standard non-esterified fatty acid in this work. The electrochemical techniques employed are cyclic voltammetry, linear sweep voltammetry, chronoamperometry and electrochemical impedance spectroscopy. Enzyme electrodes were fabricated using the layer-by-layer immobilization of alternating polymer and enzyme combinations on carbon, cobalt phthalocyanine and single wall carbon nanotube screen printed electrodes. A chronoamperometric non-esterified fatty acid sensor was developed with the linear detection range of 0.10 mM to 0.90 mM oleic acid and with a sensitivity of 0.6562 A/mM oleic acid. This sensor was then further fabricated to detect non-esterified fatty acid concentrations in human plasma and serum samples. Commercial UV optical methods were used as method of validation of the blood sample concentrations. This work produced a platform for further non-esterified fatty acid detection studies.EPSRC