A new red fluorescent probe based on rosamine-phenothiazine for the highly selective and rapid detection of hypochlorite and its bioimaging in live cells

In this study, a new water-soluble rosamine-based fluorescent probe (RClO) was designed and prepared to detect ClO- with rapid response and high selectivity, and utilized the oxidation of S atom in phenothiazine by ClO- to form a sulfoxide-type structure. The fluorescence intensity of the probe was enhanced by 120-fold after reacting with HOCl, with fast response time (similar to 20 s). The limit of detection (LOD) for ClO- was obtained as 17.8 nM from a fluorescence titration experiment. The recognizing mechanism was based on donor-excited photo-induced electron transfer (d-PeT), which rationalized with the theoretical calculations and was successfully consistent with the Mass spectral analysis. Due to the rapid response speed and very low detection limit of the probe for ClO-, it was successfully applied to image HOCl in living cells.