A ratiometric fluorescent probe for hypochlorous acid and its biological applications

We present a lysosome-targetable and ratiometric fluorescent probe, TJ2, for visually monitoring exogenous and endogenous HOCl in living cells by using a built-in S atom within the a-extended rhodamine fluorophore as a pH-independent recognition site. Based on the oxidation-promoted intramolecular charge transfer processes, TJ2 demonstrates fast ratiometric fluorescence response, excellent selectivity, and high sensitivity (2.3 nM) toward HOCl. Furthermore, TJ2 is highly lysosome-targetable, which could be used for ratiometric monitoring of the levels of HOCl in lysosomes.