A unique iridium(III) complex-based chemosensor for multi-signal detection and multi-channel imaging of hypochlorous acid in liver injury

Although hypochlorous acid (HOCl) has long been associated with a number of inflammatory diseases in mammalian bodies, the functions of HOCl in specific organs at abnormal conditions, such as liver injury, remain unclear due to it high reactivity and the lack of effective methods for its detection. Herein, a unique Ir(III) complex-based chemosensor, Ir-Fc, was developed for highly sensitive and selective detection of HOCl. Ir-Fc was designed by incorporating a ferrocene (Fc) quencher to a Ir(III) complex through a HOCl-responsive linker. In the presence of HOCl, the fast cleavage of Fc moiety in less than 1 s led to the enhancement of photoluminescence (PL) and electrochemical luminescence (ECL), by which the concentration of HOCl was determined by both PL and ECL analysis. Taking advantages of excellent properties of Ir(III) complexes, optical and electrochemical analyses of the response of Ir-Fc towards HOCl were fully investigated. Followed by the measurements of low cytotoxicity of Ir-Fc by MTT analysis, one-photon (OP), two-photon (TP) and lifetime imaging experiments were conducted to visualise the generation of HOCl in live microphage and HepG2 cells, and in zebrafish and mouse, respectively. Furthermore, the generation and distribution of HOCl in liver cells and liver injury of zebrafish and mouse were investigated. The results demonstrated the applicability of Ir-Fc as an effective chemosensor for imaging of HOCl generation in mitochondria of cells and liver injury in vivo, implying the potential of Ir-Fc for biomedical diagnosis and monitoring applications.