Bioimaging of hypochlorous acid using a near-infrared fluorescent probe derived from rhodamine dye with a large Stokes shift

Hypochlorous acid (HClO) is a bioactive molecule that bears an important function in various physiological and pathological processes such as cell signal transduction, pathogen invasion, and redox balance regulation. The near-infrared (NIR) fluorescent probe with a large Stokes shift for bioimaging of HClO is envisioned to outperform other fluorescence probes with following advantages: greater penetration depth, smaller overlap between emission and absorption spectra, and greater reduction in false results caused by the excitation light and the scattered light, aiming to achieve selective and sensitive bioimaging of HClO in vivo. Herein, a NIR fluorescent probe, TJM, was synthesized by modifying the structure of rhodamine dye to make it water soluble and biocompatible for living cells. Under being excited at 585 nm, TJM exhibits an emission peak at 730 nm with a large Stokes shift of 145 nm. TJM also provides a fast NIR fluorescent response to HClO with excellent selectivity, high sensitivity, and low detection limit (0.11 μM). The fluorescence intensity of TJM is triggered by HClO based on HClO-induced oxidization of dibenzoyl hydrazine to dibenzoyl diimide, allowing imaging of HClO in living cells, zebrafish, and different disease mice models. TJM has been demonstrated a suitable NIR probe for imaging endogenous HClO in biological systems.