Superoxide electrochemical sensors and biosensors: principles, development and applications

This chapter focuses on electrochemical methodologies used for O2 •‑ determination, and highlights the recent attempts on this aspect by using SODs. A combination of the promoted direct electron transfer of the SODs with the biomolecular recognition by virtue of specific and significant enzyme–substrate reactivity of the SODs toward O2 •‑ essentially results in a sensitive measurement of O2 •‑ without a virtual interference from physiological levels of H2O2, ascorbic acid (AA), uric acid (UA), and metabolites of neurotransmitters. Furthermore, these strategies can be further accomplished with carbon fiber microelectrodes, which can be readily employed for in-vivo determination of O2 •‑ in biological systems. Most of the SOD-based first-generation biosensors reported thus far have been based on the detection of H2O2 produced from the SOD dismutation of O2 •‑ . Mesaros and coworkers have designed an amperometic O2 •‑ biosensor at the platinum electrode with electropolymerized pyrrole film containing SOD, in which the biosensor was demonstrated to have a low detection limit, good temperature stability, and short response time. The second-generation O2 •‑ biosensors are mainly based on the electron transfer of SOD shuttled by surface-confined or solution-phase mediators whereas development of SODs-based third-generation O2 •‑ biosensors are based on the direct electron transfer properties of the SODs. Even though the demonstrated good analytical properties of the SOD-based biosensors, such as low detection limit and high selectivity, substantially make them very efficient for in-vivo determination of O2 •‑, the miniaturization of those SOD-based biosensors remains essential for such purposes. The excellent properties of electrochemical O2 •‑ biosensors can substantially guarantee these miniaturized biosensors a great potential for real-time monitoring of O2 •‑ in biological tissues, such as brain tissues in future.