ABSTRACT

Hypochlorous acid (HOCl) acts as a weak acid distributed mainly in acidic organelle lysosomes of phagocytes and plays a crucial role in the immune defense. The elaborate interrelation between the variations of HOCl levels in lysosomes and different physiological and pathological processes remains unclear. Thus, the accurate determination of lysosomal HOCl in living cells and in vivo is very important. Because of extremely low concentration and difficulty in distinguishing HOCl from OCl under the physiological environment, it is still a great challenge to specifically monitor the intracellular intrinsic HOCl levels without exogenous stimulation, which impedes an exact understanding of its biological roles. In this paper, based on the electrophilic addition of Cl to sulfide moiety, we have developed a two-photon fluorescent probe O-(N-butyl-1,8-naphthalimide)-4-yl-N,N-dimethylthiocarbamate (NDMTC) for the specific determination of HOCl over OCl and other bioactive molecules. Our results show that NDMTC possesses a detection limit of 7.6 pM, and it is the first fluorescent probe for detecting HOCl at the picomolar level. Furthermore, by introducing an alkylmorpholine group to the NDMTC framework, the lysosome-targetable derivative Lyso-NDMTC was obtained, and its ability to image HOCl in the lysosome organelles was clearly confirmed. Combined with two-photon fluorescence imaging of background suppression and deeper tissue penetration, NDMTC and Lyso-NDMTC were used to successfully visualize intracellular native HOCl and discern tumor tissue in mice. This study offers two perfect fluorescence imaging probes for further investigation of pathological roles of HOCl in various diseases.

Hydrogen sulfide (H2S) is an endogenous gaseous signaling molecule in many physiological processes. Relevant investigations indicated that H2S plays a cytoprotective effect under endoplasmic reticulum stress. Currently, it is still a challenge to design effective methods for ratio detection of endoplasmic reticulum H2S. Herein we are the first to construct a ratiometric near-infrared fluorescent probe (M-H2S) for sensing H2S in the endoplasmic reticulum. M-H2S has high selectivity and sensitivity toward H2S (LOD = 39.1 nM). Additionally, M-H2S possessed an excellent endoplasmic reticulum targeting ability. Moreover, M-H2S was successfully utilized to visualize exogenous/endogenous H2S in HeLa cells and zebrafish. Particularly important, endogenously produced H2S was observed under endoplasmic reticulum stress induced by tunicamycin.

No abstract

Mercury (Hg) and its derivatives pose a serious threat to the environment and human health because of their durability, easy transference and high biological accumulation. Thus, the development of methods for selective and sensitive determination of Hg 2+ is very important to understand its distribution and implement more detailed toxicological studies.Herein, we report a simple 4-hydroxynaphthalimide-derived fluorescent probe (1) for the detection of both inorganic and organic mercury species in aqueous solution. Probe 1 could quantificationally detect mercury species by fluorescence spectroscopy with high selectivity and sensitivity. Importantly, probe 1 could serve as a "naked-eye" indicator for mercury species and exhibited a large fluorescent enhancement with the help of hydrogen peroxide (H 2 O 2 ). Additionally, the mechanism of the reaction between probe 1 and mercury species was confirmed using 1 H-NMR and ESI-MS. And, analytical applications of probe 1 to the river water samples further demonstrated that it provided an excellent method for the determination of mercury species in the environment.