A fast-responsive two-photon fluorescent probe for in vivo imaging superoxide radical anion with a large stokes shift

A novel and simple two-photon fluorescent probe NS-O for the detection of superoxide radical anion (O-2(center dot-)) with a large turn-on fluorescence signal is presented. The probe NS-O exhibited favorable properties including fast response, high selectivity, large stokes shift, low cytotoxicity and almost 100-fold fluorescence enhancement in solution. The two-photon probe could be applied to monitor endogenous superoxide radical anions in living cells and tissues. Notably, the two-photon fluorescent probe NS-O could be used to image superoxide radical anions in zebrafish.