Xianshun Zeng

Fluorescence probe for hypochlorous acid in water and its applications for highly lysosome-targetable live cell imaging

Hypochloric acid (HOCl) plays important roles in cell signaling and homeostasis, such as anti-inflammation and immune regulation, pathogen response and so on. Accordingly, direct detection of HOCl at the organelle level is important for investigation of the complex contributions of HOCl to human health. In the present study, a water soluble lysosome-targeting fluorescent probe Lyso-1 bearing a hydrazone moiety as a HOCl-responsive site and a morpholine unit as a lysosomal-targeting group has been synthesized and evaluated for its ability to image lysosomal HOCl. The probe Lyso-1, based on a novel HOCl-promoted hydrazone oxidation strategy, showed a highly selective fluorescent off/on response to HOCl with the various reactive oxygen species in water. With increasing amount of ClO- from 0.5 to 2.5xa0μM, a linear correlation between the fluorescence intensity (570xa0nm) of Lyso-1 and [ClO-] was found, and the regression equation was yxa0=xa096.65xa0+xa0110.2068[ClO-] with a linear coefficient R of 0.9920. The detection limit is determined to be 60xa0nM. Lyso-1 demonstrated a perfect lysosomal targetable ability, and was successfully applied to image of exogenous, endogenous produced lysosomal HOCl in live L929xa0cells. The success of subcellular imaging indicated that the lysosome-targetable probe Lyso-1 could be used in further applications for the investigation of biological functions and pathological roles of HClO at organelle levels.

A highly selective and sensitive fluorescent probe for hypochlorous acid and its lysosome-targetable biological applications

A novel lysosome-targetable fluorescence probe PT-1 based on a photoinduced electron transfer (PET) mechanism has been designed and synthesized. For comparison, the probe PT-2 without morpholine moiety as a lysosome-directing group was also synthesized and investigated. Probes PT-1 and PT-2 exhibited high selectivity, high sensitivity (with the detection limits down to the 10-10M range) and response in real time (within 10s) toward HOCl over other reactive oxygen species (ROS). Both PT-1 and PT-2 were cell permeable and enabled them to be used for monitoring of HOCl in living cells. Meanwhile, the probe PT-1 demonstrated an accurately lysosome-targeting ability, and was successfully applied to image of exogenous, endogenous produced HOCl in living cells. The success of subcellular imaging suggested that the probe PT-1 could be used in further applications for the investigation of biological functions and pathological roles of HOCl at organelle levels.

A rhodamine-based fast and selective fluorescent probe for monitoring exogenous and endogenous nitric oxide in live cells

Nitric oxide, an important cellular messenger molecule, plays a wide range of physiological roles in neurotransmission, vascular relaxation, platelet activation, and immune response. In this work, we synthesized a selective and sensitive cationic fluorescent probe (ROPD) for monitoring exogenous and endogenous nitric oxide in live cells by grafting a NO-trapper o-phenylenediamine (OPD), via one of the amino groups of OPD, onto a rhodamine fluorophore at the C-3 position. The probe exhibited high selectivity and sensitivity towards NO with fast response in the water phase over a wide pH range. At the same time, the probe ROPD is cell-membrane permeable and can be used for the real-time visualization of exogenous NO in both L929 and HeLa cells, and endogenous NO in stressed RAW 264.7 cells.

Synthesis and bioapplication of a highly selective and sensitive fluorescent probe for HOCl based on a phenothiazine–dicyanoisophorone conjugate with large Stokes shift

Herein, a fluorescent probe, Dcp-EPtz, for HOCl based on a strong push–pull phenothiazine–dicyanoisophorone conjugate was prepared. The probe exhibits a very large Stokes shift of over 170 nm. Dcp-EPtz turns out to be a fast-responsive (<10 s) fluorescent probe for HOCl with high selectivity and sensitivity. It shows a good linear relationship between the enhanced fluorescence intensity at 617 nm and the concentration of hypochlorous acid in the range 0–10 μM, with the detection limit of 3.9 × 10−8 M. Moreover, the probe Dcp-EPtz exhibits the ability for endogenous HOCl monitoring in living cells.