Engineering HClO Ratiometric Fluorescent Probe by Inducing Molecular Aggregation to Suppress TICT Formation for...

Developing highly specific hypochlorite (HClO) ratiometric fluorescent probes for elucidating drug-induced liver injury (DILI) and related biological issues is of great significance. Phenothiazine-derived coumarin (PTZC) fluorophores have been shown to exhibit high specificity in response to HClO; however, such fluorophores emit dim fluorescence in aqueous media due to the intrinsic twisted intramolecular charge transfer (TICT) effect, resulting in only a turn-on mode response to HClO. In this work, we present a molecular design strategy of suppressing the TICT formation by inducing PTZC fluorophores to form nanoaggregates in aqueous media for the HClO ratiometric fluorescent probe design. The probe PBFF developed based on this strategy can form considerable nanoaggregates in aqueous media to inhibit the TICT formation without suffering from the aggregation-caused quenching effect, thus allowing it to emit intense fluorescence in aqueous media (Φf = 0.20). Importantly, PBFF can specifically and sensitively (LOD = 15.7 nM) respond to HClO, showing distinct ratiometric fluorescence changes. Further experimental results show that PBFF can sensitively monitor in situ DILI progression through HClO-induced fluorescence ratio changes. This strategy of suppressing TICT formation by inducing molecule aggregation in aqueous media will advance the development of ratiometric fluorescent probes in the future.