Bioimaging of superoxide anions in living cells and in vivo: Perfect visualization with fluorescence probes and their applications

Superoxide anions (O 2 •─ ), which are precursors of reactive oxygen species (ROS), are mainly produced in the mitochondria. This precursor of ROS is involved in both pathological and physiological processes, hence their role in many disease conditions and complications is pivotal. Though with time they are capable of being changed into related ROS species, their quantification will aid in targeting and complete eradication through numerous chemical reactions. The presence of a high reduction potential fosters the innate anionic charge to impede their reactivity with centers considered to be electron-rich. Though there are numerous quantification processes for the O 2 •─ , the use of a fluorescent probe which serves as a low invasive approach with deep tissue penetration and prolonged time of analysis has emerged to change the status quo when it comes to the way of analyzing O 2 •─ . Although, in some cases, this approach happens to be faced with some difficulties such as autofluorescence, photobleaching, shallow penetration, etc. This review seeks to give a general overview of the recent development in this research field, outcomes, and the yield of employing Two-photon, NIR, and other ratiometric fluorescent probes, their ability to sensitively and selectively target O 2 •─ in vivo and in vitro . Superoxide anions are involved in both pathological and physiological processes, playing a huge role in most disease conditions of an organism. Fluorescent probe possesses properties that allow the non-invasive means of quantification, imaging, and monitoring of these superoxide anions through either one-photon, two-photon fluorescence imaging, or a combination of both qualities in vivo and in vitro . • Fluorescence probes present a low-invasive means for O 2 . •─ detection. • Fluorescence probes sensitively and selectively target O 2 . •─ in cells for bioimaging. • Detection of O 2 . •─ provides a means of diagnosis of related physiological conditions.