Three-in-One: A Multifunctional Fluorescent Probe for Sensing Hypochlorite, Oxyammonia, and Viscosity in Biosystems

In this study, a novel phenothiazine-cyanoacetate-based fluorescent probe, NS-CY, was developed for the simultaneous detection of hypochlorite (ClO^-), oxyammonia (NH₂OH), and viscosity, utilizing triresponse signals. Initially, the probe exhibits red fluorescence at 642 nm under aqueous media. In high-viscosity environments, the inhibition of intramolecular bond rotation within NS-CY activates the fluorescence emission at 492 nm, resulting in strong green fluorescence. Concurrently, ClO^--induced oxidation of the phenothiazine moiety to a sulfoxide product causes a significant blue shift in emission from 642 to 548 nm, generating yellow fluorescence. Upon reacting with oxyammonia, the fluorescence at 642 nm decreases gradually, which exhibits a turn-off pattern. Furthermore, the probe was successfully applied to monitor viscosity increases induced by ferroptosis caused by erastin in living cells. Notably, NS-CY effectively tracked both ClO^- and oxyammonia in zebrafish, which demonstrates its potential application in related early diagnosis and medical intervention.