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Biothiols such as cysteine (Cys), homocysteine (Hcy) and glutathione (GSH) play significant roles in maintaining biological homeostasis in organisms. Due to their particular significance in the physiology and pathology of humans, accurate determination and differentiation of Cys, Hcy, and GSH for understanding their roles in related diseases are in urgent demand. Herein, a new fluorescent probe NIPY-NBD was designed and synthesized for the detection of Cys/Hcy and GSH. The probe exhibits a variety of excellent properties including high sensitivity and low cytotoxicity as well as good cell membrane permeability. Furthermore, the probe showed a 100-fold (λex/em = 310 nm/520 nm) and 210-fold (λex/em = 340 nm/550 nm) fluorescence enhancement when reacted with Cys in buffer, and could swiftly respond to Cys and Hcy within 2.5 min. NIPY-NBD was further applied successfully in imaging in A549 cells and xenograft mouse tumor tissues. Taken together, NIPY-NBD may have great potential in detecting and distinguishing Cys/GSH in living animals and could be applied in tumor diagnosis. [ABSTRACT FROM AUTHOR]

Hydrogen sulfide (H2S) is one of the endogenous regulators of many physiological processes. NIPY-OH based on an imidazo[1,5-α]pyridine has a large Stokes shift, high photostability with green-emission, relatively high fluorescence quantum yield. NIPY-OH could serve as an excellent candidate for the design of fluorescent probes. However, the reported probes cannot sufficiently take advantage of the optical properties of NIPY-OH due to the water-soluble problem. Herein, a new fluorescent probe NIPY-PBA, based on NIPY-OH, was designed for the detection of hydrogen sulfide. By rational design, compared with other probes, we successfully obtained the probe with higher sensitivity (limit of detection = 43 nM) and shorter response time (1.5 minutes) due to better water solubility. NIPY-PBA maintained the excellent optical properties of a 230-fold fluorescence enhancement with a large Stokes shift (208 nm) at the same time. Furthermore, NIPY-PBA was applied for the fluorescence imaging of H2S in living cells with low cytotoxicity, indicating NIPY-PBA has great potential to monitor H2S in biological systems. [ABSTRACT FROM AUTHOR]

Two new β-diketone-boron difluoride based near-infrared fluorescent probes 1 and 2 which exhibit polarity sensitivity have been designed and synthesized. Probes 1 and 2 are composed of a β-diketone-boron difluoride moiety as an acceptor unit, and a diethylamino group and a phenolic hydroxyl group as donor units. The long conjugate structures form a "donor–acceptor–donor" configuration, induce intramolecular charge transfer (ICT), and confer near-infrared fluorescence emission and excellent polarity sensitivity. The photophysical properties of these two probes were investigated in detail. Experimental data demonstrated that as the environmental polarity decreased, the fluorescence intensity of the probes increased obviously, accompanied by a blue-shift of the maximum emission wavelength. In addition, these two probes were photostable and solely sensitive to polarity without interference from viscosity, pH and common active species. Theoretical calculations indicated that probes 1 and 2 displayed lower energy gaps and faster non-radiative decay in polar solvents. Furthermore, probes 1 and 2 were utilized to quantitatively detect the polarity of a binary mixture through the satisfactory linear relationship between the fluorescence emission intensity ratios and the orientation polarizability of the mixed solvent. Additionally, probe 1 was successfully utilized to visualize the polarity distribution of live cells. Both of these probes are perfect candidates for studying polarity in vitro and even in live systems. [ABSTRACT FROM AUTHOR]

The tridentate ligand 2,4,6-tris(2-(pyridin-4-yl)vinyl)-1,3,5-triazine (TPVT) was designed and synthesized. We prepared metal–organic framework (TPVT-MOFs) crystals containing TPVT, 1,3,5-benzenetricarboxylic acid and cobalt by solvothermal reaction. Then, a series of composite materials with different contents of TPVT-MOFs were obtained by combining TPVT-MOFs with g-C3N4. Due to the interaction between TPVT-MOFs and g-C3N4, the composite materials have a more favorable valence band (VB) and conduction band (CB) for photocatalytic reduction of CO2 and oxidation of H2O. Under the conditions of visible light and a gas–solid system without a co-catalyst, a photosensitizer and a sacrificial agent, the yield of CO2 reduction by TPVT-MOFs@g-C3N4-10 can reach 56.4 μmol·g−1·h−1, which is 3.2 times that of pure g-C3N4 (17.5 μmol·g−1·h−1). The results of DFT calculations showed that the adsorption of H2O on the TPVT-MOFs@g-C3N4 composite material was more preferential, which promoted the adsorption and reduction of CO2. [ABSTRACT FROM AUTHOR]

Mitochondria as essential organelles play critical roles in cellular metabolism. Mitochondrial pH is a vital parameter that directly affects the unique function of mitochondria. Herein, we present a new ratiometric fluorescent probe M-pH for monitoring the pH within the mitochondria. M-pH consists of a stable and large π-electron conjugated merocyanine system. The lipophilic cationic benzyl group will facilitate the accumulation of M-pH in mitochondria. The phenol unit is the recognition moiety, achieving the ratiometric sensing of pH changes. The experimental results indicate that M-pH displays ratiometric fluorescence response to different pH values. Meanwhile, M-pH shows negligible response to common species, and has high stability and low cytotoxicity. In biological experiments, M-pH can solely accumulate in mitochondria and visualize the pH changes during mitophagy and cell apoptosis. We thus believe that M-pH has great potential as a practical tool for real-time monitoring of pH changes of mitochondria, contributing to revealing the pathogenesis of mitochondrial pH associated diseases. [ABSTRACT FROM AUTHOR]

Hydrogen sulfide (H2S), an endogenous gaseous signalling molecule, has attracted attention in biochemical research. The detection of H2S in living systems is essential for studying its functions. Although a variety of probes have been reported for the detection of cellular H2S, the development of rapid, highly selective and sensitive near-infrared (NIR) probes for in vivo detection of H2S still remains a challenging target. Herein we synthesized a near-infrared fluorescent probe Cy-PBA, with good selectivity, high sensitivity (limit of detection = 21 nM) and rapid response time (＜1.5 minutes). Importantly, Cy-PBA was successfully applied for fluorescence imaging of H2S in living cells, mice and tissues with low cytotoxicity, indicating that it owns broad application prospects in the detection of H2S in biological samples. [ABSTRACT FROM AUTHOR]