**6.1 Glucose oxidase-based biosensor**

Clark and Lyons discovered the first electrochemical biosensor in 1962 using a glucose oxidase-based glucometer. Electrochemical glucose biosensors dominate the market due to their superior sensitivity, repeatability, maintenance simplicity, and low price. They come in conductometric, amperometric, and potentiometric varieties [16–19]. The D-glucose oxidation is catalyzed by immobilized glucose oxidase (GOx) in a biosensor of glucose that uses molecular oxygen, resulting in the production of hydrogen peroxide and gluconic acid [20]. A typical enzyme used in biosensors, GOx, has a slightly better selectivity for glucose. Less strict production conditions are achievable since GOx can survive more pH, ionic strength, and temperature fluctuations than many other enzymes [20, 21]. The glucose biosensor consists of an oxygen electrode, an inner semipermeable membrane, a thin layer of GOx, and an outside dialysis membrane. Enzymes can be immobilized to create an enzyme electrode for electrochemical detection. Updike and Hicks improved the electrochemical glucose assay by immobilizing and stabilizing GOx, measuring glucose levels in body fluids for the first time [16, 22]. Due to its high sensitivity and selectivity, cheap cost, and improved patient compliance, glucose oxidase-based biosensor technology is growing to be a significant competitor in the field of glucose-level monitoring [17].
