Superoxide Electrochemical Sensors and Biosensors: Amperometric, Impedimetric Sensors and Enzyme-Based Electrosensor Applications

Abstract

The ever-increasing demand for sensors, coupled with the quick speed of technological advancement, has created a vast and dynamic world of sensors.  The agricultural, food, and oil sectors, as well as environmental and medicinal applications, all make extensive use of electrochemical sensors due to their low cost and ease of use in detecting changeable analytes.  The low theoretical detection limits that arise from the differences in the Faradaic and nonFaradaic currents, as well as the variability of the reporting signals (e.g., voltage, current, overall power output, or electrochemical impedance) are the two primary reasons why electrochemical sensing is so popular.  Also covered is the part nanoparticles play in the development and study of electrochemical sensors.  We hope that the data given here will inspire researchers to keep digging into the topic of electrochemical sensors.  In medical applications, electrodes are useful for detecting superoxide and nitric oxide, two species with very short half-lives.  They can open the door to a spatially and temporally resolved study that sheds light on the physiological function and interplay of the two radicals.  Electrodes that have been modified with cytochrome c or superoxide dismutase as recognition elements are predominantly used in superoxide sensing.  The method relies on either direct electrochemistry of proteins or the detection of products of superoxide breakdown to function.  The majority of the electrodes used for NO measurement have been upgraded with gas-permeable membranes.  By reducing the applied electrode potential, transition metal complexes have been used to improve NO electrocatalysis.  Electrodes incorporating hemoproteins is a more recent development.  Using the unique interaction between NO and the haem group, NO sensing can be achieved by direct protein-electrode interactions.  Both the extracellular and intracellular regions of living cells contain extremely low amounts of superoxide and hydrogen peroxide, and these species have a limited half-life due to the presence of a complex antioxidant system that rapidly consumes them.  Living cell production of superoxide and hydrogen peroxide makes real-time monitoring of these compounds a significant challenge.  Cells can continually create superoxide or hydrogen peroxide, which can be monitored using biosensors and electrochemical sensors that are appropriately built.  Therefore, they are in a good position to finish analytical procedures that provide endpointsand/or indirect evidence of these species' overproduction by cells.  Despite the abundance of reports on electrochemical sensors for hydrogen peroxide and superoxide, there is a dearth of literature detailing their application in cellular biology.  Additionally, the majority of these articles do not detail comprehensive research but rather projects that only go as far as a proof of principle.