Electrochemical enzyme assays and biosensors
Enzymes are biological catalysts of great scientific and economic importance with a billion-dollar market. Their quantification is important because they play a vital role in cellular processes, which makes them therapeutic targets for drug development. Therefore, there is a high demand for simple and cost-effective assays to quickly evaluate their catalytic activity. There is also a need to develop better enzyme-based biosensors for clinically significant species. These topics are the focus of the five research projects presented in this Dissertation. The first project (Chapter 5) describes an internally calibrated electrochemical continuous enzyme assay, ICECEA, for the rapid determination of redox enzymes (xanthine oxidase, lactate dehydrogenases, alcohol dehydrogenase) that are biomarkers of systemic human diseases. The second project (Chapter 6) tests the limits of ICECEA in the determination of aspartate transaminase as a biomarker of liver function. The third project (Chapter 7) studies the mechanism of electrochemical glucose biosensor based on the glucose dehydrogenase, redox nanoparticles (silica-azure), and carbon nanotubes. The fourth project (Chapter 8) explores the unconventional modes of signal amplification in biosensors based on alcohol dehydrogenase, glucose 6-phosphate dehydrogenase, glycerol 3-phosphate dehydrogenase, and glucose oxidase (GOx). In the fifth project (Chapter 9), a direct electron transfer (DET) between GOx and carbon nanotubes (CNT) is examined in the context of glucose detection leading to the refusal of "DET in the GOx/CNT system", the fallacy that has been polluting sensor literature for years.