Deep-Red AIE-Active Fluorophore for Hypochlorite Detection and Bioimaging in Live Cells

Hypochlorite (ClO–) is widely presented in daily life and human body. An appropriate amount of hypochlorite may help the body regulate the immune system, while excessive hypochlorite can cause a variety of diseases. Herein, a novel fluorescence probe PTZ-BT containing a large conjugate plane was designed and synthesized. It exhibited a large Stokes shift of 158 nm and extreme AIE activity and emitted deep-red fluorescence (∼642 nm). Moreover, PTZ-BT showed specific turn-off fluorescent-responsive and high-sensitive detection (detection limit equals to 0.64 μM) toward ClO– in PBS buffer solutions. Job's plot showed that the binding stoichiometry of PTZ-BT with ClO– was 1:1. It was further demonstrated that sulfur atoms in the phenothiazine groups were oxidized to sulfoxide by ClO–, resulting in fluorescence quenching supported by high-resolution mass spectrometry. In addition, PTZ-BT was used for bioimaging in HepG-2 cells with low cell toxicity and good cell permeability. Furthermore, live cells studies also demonstrated PTZ-BT can detect exogenous ClO– inside live cells.