An ultrasensitive electrochemical sensor based on cotton carbon fiber composites for the determination of superoxide anion release from cells.

A sensor is described for determination of superoxide anion (O˙). The electrode consists of nitrogen-doped cotton carbon fiber (NCFs) modified with silver nanoparticles (AgNPs) which have excellent catalytic capability. The resulting sensor, best operated at working potentials around -0.5 V (vs. SCE), can detect O˙ over an extraordinarily wide range that covers 10 orders of magnitude, and the detection limit is 2.32 ± 0.07 fM. The electrode enables the release of O˙ from living cells under normal or under oxidative stress conditions to be determined. The ability to scavenge the superoxide anions of antioxidants was also investigated. In the authors' perception, the method represents a viable tool for studying diseases related to oxidative stress. Graphical abstract Schematic presentation of the construction of an electrochemical sensor based on Nitrogen-doped cotton carbon fiber and silver nanoparticles. It can be used for the direct detection of superoxide anions released from Glioma cells (U87) under normal or under oxidative stress conditions.