Recent development of synthetic probes for detection of hypochlorous acid/hypochlorite.

Hypochlorous acid/hypochlorite (HOCl/OCl-), as one of the most important reactive oxygen species (ROS), plays an important role in various physiological and pathological processes. Nonproperly located or abnormal concentration of OCl-, however, is associated with many diseases. Thus, developing the fluorescent probe for detecting OCl- is of great significance. To this end, in last decade, many fluorescent probes have been developed and applied for detecting HOCl/OCl- in vitro and in vivo. Despite a great progress has achieved, the development and application of near-infrared fluorescent HOCl/OCl- probe still have some challenges. For example, highly specific and sensitive NIR fluorescent HOCl/OCl- probes applied in endogenous OCl- detection and subcellular organelle bioimaging. In this review, we summarized the representative cases of HOCl/OCl- probes with properties that mentioned above. The discussion contains design strategies, detection mechanisms, as well as applications in bioimaging.

Ratiometric and colorimetric fluorescent probe for hypochlorite monitor and application for bioimaging in living cells, bacteria and zebrafish.

Hypochlorous acid (HOCl)/hypochlorite (ClO-) was a biologically important component of reactive oxygen species (ROS) and plays a key role in human immune function systems. HOCl/ClO- can destroy invasive bacteria and pathogens, and mediate the physiological balance of the organism with low concentrations, and cause oxidation of the biomolecules such as proteins, cholesterol and nucleic acid in biological cells, leading to a series of diseases with over capacity. Therefore, quantifying the content of HOCl/ClO- in organisms are extremely urgent. In this work, coumarin-salicylic hydrazide Schiff base (CMSH), a ratiometric and colorimetric fluorescent probe for ClO- detection based on coumarin as the fluorophore unit was rationally designed and synthesized. The results indicated that CMSH exhibits high selectivity and sensitivity for ClO- identification. Additionally, the ratios (I470/I532) displayed brilliant ClO--dependent quick and sensitive performance within 40 s and limitation of 128 nM, respectively. As well as the color of the solution changes from green to colorless accompanied by the fluorescence form green turns into blue with addition of ClO-. Totally, CMSH has been successfully employed as ratiometric sensor to image in living cells, bacteria and zebrafish with low cytotoxicity and good permeability.

A ratiometric fluorescence probe based on a novel recognition mechanism for monitoring endogenous hypochlorite in living cells.

A ratiometric fluorescence probe (named ZOC) for the fast detection of HClO/ClO- was constructed by coumarin (donor) and pyridinium (acceptor) based on Forster resonance energy transfer (FRET) and intramolecular charge transfer (ICT) platform. ZOC possessed red emission signal (610 nm), large Stocks shift (190 nm), high energy transfer efficiency (95.3%), high selectivity and sensitivity, low detection limit (25 nM), wider detection range (from 25 nM to 30 µM), rapid response (within 13 S), and good biocompatibility. It was very interesting that the recognition mechanism involved a new organic reaction in which olefin double bond reacted first with HClO/ClO- regioselectively, followed by cyclization. ZOC was successfully used to the real time detection of endogenous HClO/ClO- in RAW 264.7 cells.