Detection of superoxide in cells, tissues and whole organisms

The radical anion of dioxygen superoxide (O2.-) is a physiological free radical formed in various enzymatic processes. On the one hand superoxide is a precursor of reactive oxygen and nitrogen species (hydroxyl radicals, peroxy radicals, hydrogen peroxide, peroxynitrite, etc.), -the initiators of cellular damage; on the other hand it is a signaling molecule regulating numerous physiological processes including apoptosis, aging, and senescence. Therefore, the detection and measurement of superoxide in cells, tissues, and whole organisms is of a vital importance for in vitro and in vivo studies of many physiological and pathophysiological processes. At present different efficient methods were developed, which allow to identificate and measure superoxide in biological systems. In present review the credibility and efficiency of principal mostly applied methods of superoxide detection based on one-electron transfer and nucleophilic reactions are discussed, and spectrophotometrical, chemiluminescent, fluorescent, and ESR spin trapping methods are compared.