In vivo real-time measurement of superoxide anion radical with a novel electrochemical sensor

Abstract The dynamics of superoxide anion (O 2 − ) in vivo remain to be clarified because no appropriate method exists to directly and continuously monitor and evaluate O 2 − in vivo. Here, we establish an in vivo method using a novel electrochemical O 2 − sensor. O 2 − generated is measured as a current and evaluated as a quantified partial value of electricity ( Q part ), which is calculated by integration of the difference between the baseline and the actual reacted current. The accuracy and efficacy of this method were confirmed by dose-dependent O 2 − generation in xanthine–xanthine oxidase in vitro in phosphate-buffered saline and human blood. It was then applied to endotoxemic rats in vivo. O 2 − current began to increase 1 h after lipopolysaccharide, and Q part increased significantly for 6 h in endotoxemic rats, in comparison to sham-treated rats. These values were attenuated by superoxide dismutase. The generation and attenuation of O 2 − were indirectly confirmed by plasma lipid peroxidation with malondialdehyde, endothelial injury with soluble intercellular adhesion molecule-1, and microcirculatory dysfunction. This is a novel method for measuring O 2 − in vivo and could be used to monitor and treat the pathophysiology caused by excessive O 2 − generation in animals and humans.