Lintao Zeng

A mitochondria-targeted ratiometric fluorescent probe for rapid, sensitive and specific detection of biological SO2 derivatives in living cells.

In this study, we report a ratiometric fluorescent probe (CZBI) for sulfur dioxide (SO2) derivatives based on the conjugate of carbazole and benzo[e]indolium, which displays colorimetric and ratiometric fluorescence dual response to HSO3(-). The probe can quantitatively detect HSO3(-) with high specificity, fast response (within 40s) as well as low detection limit (10nM). A 1,4-nucleophilic addition reaction was proposed for the sensing mechanism of this probe, which was confirmed by (1)H NMR and HR-MS spectra. Fluorescence co-localization studies demonstrated that CZBI was a specific mitochondria-targeted fluorescent probe for SO2 derivatives with excellent cell membrane permeability. Furthermore, fluorescence imaging of HeLa cells indicated that CZBI could be used for monitoring the intrinsically generated intracellular SO2 derivatives in living cells by ratiometric fluorescence imaging. Thus, CZBI has a great potential application for exploring the role played by SO2 derivatives in biology.

A simple naphthalene-based fluorescent probe for high selective detection of formaldehyde in toffees and HeLa cells via aza-Cope reaction.

A simple naphthalene-based fluorescent probe (AENO) for formaldehyde (FA) was successfully synthesized, which exhibited a significant fluorescence turn-on response towards FA in aqueous solution. The probe could quantitatively determine the concentration of FA (0-1.0mM) with excellent selectivity, high sensitivity and low limit of detection (0.57µM). The sensing mechanism was proposed as 2-aza-Cope rearrangement for AENO after reaction with FA, which was confirmed by (1)H NMR, HR-MS, FT-IR, UV-vis and fluorescence spectra. The probe has been employed to determine the FA contents in several commercially available toffee samples with satisfactory performance. Thus, AENO might be used as a promising tool for quantitative detection of FA in food. Furthermore, fluorescence imaging of HeLa cells indicated that the probe was cell membrane permeable and could be used for visualizing/imaging the FA trace/transportation in cancer cells.

A smart fluorescent probe for simultaneous detection of GSH and Cys in human plasma and cells

Abnormal levels of glutathione (GSH) and cysteine (Cys) are associated with some diseases, thus monitoring the dynamic changes and the quantification of GSH/Cys is of great significance in clinical diagnosis. Herein, a smart fluorescent probe was developed for the detection of Cys and GSH, which was constructed with a far-red emitting indole-BODIPY and 7-nitrobenzofurazan (NBD) linked via an ether bond. Upon substitution of the ether with nucleophilic thiolate of GSH/Cys, the probe released indole-BODIPY fluorophore, which gave rise to a significant fluorescence “turn-on” signal at 635 nm. Moreover, Cys induced an intramolecular rearrangement reaction on electrophilic site of NBD, resulting in another emission band at 540 nm. Therefore, this probe can be used to simultaneously detect Cys and GSH in different emission channel. Such capability of the probe has been demonstrated for the measurement of Cys and GSH in human plasmas with fast response and low detection limit (0.64 μM). Furthermore, fluorescence imaging of HeLa cell indicated that the probe was cell membrane permeable and could be used for visualizing GSH and Cys in living cells.

A dual-channel responsive near-infrared fluorescent probe for multicolour imaging of cysteine in living cells

Aberrant levels of cysteine (Cys) in living cells are closely related to some diseases; thus in situ visualization of intracellular Cys is very helpful for the investigation of physiological and pathological processes. Herein, we report a dual-channel responsive near-infrared (NIR) fluorescent probe for multicolour imaging of Cys in living cells. The probe was constructed with a NIR BODIPY attached to 7-nitrobenzofurazan (NBD) via an ether bond. Upon substitution of the ether with the nucleophilic thiolate of Cys, a NIR BODIPY fluorophore was released to produce a significant fluorescence-enhanced signal at 735 nm. Moreover, Cys induced an intramolecular rearrangement reaction on the electrophilic site of NBD, resulting in another emission band at 540 nm. This probe exhibited some favorable properties including a dual-channel response, high fluorescence brightness, good photostability, fast response, low detection limit (22 nM) and low cytotoxicity. Furthermore, the probe was successfully applied for multicolour imaging of Cys in living cells.

A novel colorimetric and ratiometric fluorescent probe for visualizing SO2 derivatives in environment and living cells

Monitoring sulfur dioxide (SO2) derivatives in environment is of great significance due to their harmful effects to the environment and human health. In this study, a fluorescent probe (CZBT) for SO2 derivatives was prepared from 9-ethyl-9H-carbazole-3,6-dicarboxaldehyde and 2-methyl-benzothiazolium, which displayed a noticeable color change from yellow to colorless along with a remarkable fluorescence change from yellow to blue in response to HSO3-. The probe could quantitatively determine the concentration of HSO3- with excellent selectivity, high sensitivity and low limit of detection. 1H NMR and HR-MS spectra demonstrated that a selective 1, 4-nucleophilic addition occurred on the bridge double bond in CZBT. The probe was successfully used to determine the SO2 derivatives in several real water samples with good recovery. Furthermore, the probe was employed for monitoring the level of intracellular HSO3- in HeLa (human cervical cancer) cells by fluorescence imaging. These results indicated that CZBT has a good capability for monitoring SO2 derivatives in environment and living cells.

A mitochondria-targeted near-infrared probe for colorimetric and ratiometric fluorescence detection of hypochlorite in living cells

In this study, we report a near-infrared (NIR) fluorescent probe (CMBI) for the detection of hypochlorite (ClO−), which displays colorimetric and ratiometric fluorescence dual responses towards ClO−. The probe can detect ClO− with high selectivity, fast response (within 90 s) as well as low detection limit (33 nM). An oxidation reaction was proposed for the sensing mechanism, which was confirmed by 1H NMR and HR-MS spectra. Fluorescence co-localization studies demonstrated that CMBI was a specific mitochondria-targeted fluorescent probe for ClO− with excellent cell membrane permeability. Furthermore, confocal fluorescence images of HeLa cell indicated that CMBI could be used for monitoring intracellular ClO− in living cells by ratiometric fluorescence imaging.

Lysosome-targetable polythiophene nanoparticles for two-photon excitation photodynamic therapy and deep tissue imaging

Two-photon excitation (TPE) photodynamic therapy (PDT) has attracted great interest due to its distinctive properties, e.g., good penetration ability of biological tissues and less damage to healthy tissues. However, the conventional photosensitizers (PSs) for PDT have poor subcellular location capability and low two-photon absorption (TPA) cross section in the phototherapeutic window. Herein, we report a fascinating multi-functional TPE PS, polythiophene nanoparticles (PT NPs), for simultaneous lysosome-targetable fluorescence imaging and PDT. PT NPs show bright yellow fluorescence, good water solubility as well as excellent photo- and pH-stability. Moreover, PT NPs exhibit high singlet oxygen generation quantum yield (∼42%) and large TPA cross section (∼3420 GM). A fluorescence imaging penetration depth of 1800 μm could be reached in the tissue phantom under the TPE mode. Due to these outstanding merits and their unique clathrin- and caveola-independent intracellular uptake pathway, PT NPs have great potential for application in TPE fluorescence imaging and photodynamic therapy.

A hemicyanine-based colorimetric and ratiometric fluorescent probe for selective detection of cysteine and bioimaging in living cell

A new ratiometric fluorescent probe based on a hemicyanine dye was synthesized. Investigation on the response behavior towards amino acids showed that the probe had a capability of rapidly and selectively detecting cysteine over other biothiols such as glutathione and homocysteine with similar structure and reactivity, and it also displayed a high selectivity and rapid response. Moreover, the probe had good water solubility, which authorized it could be applied in fluorescent bioimaging. The laser confocal fluorescence images indicated that the probe could visualize the intracellular cysteine. This work suggested that it could be utilized as a fluorescent indicator to discriminate the endogenous cysteine in living cells.

A novel fluorescent probe for rapid and sensitive detection of hydrogen sulfide in living cells

A novel fluorescent probe for H2S was developed based on a far-red emitting indole-BODIPY, which was decorated with morpholine and 2,4-dinitrobenzenesulfonyl (DNBS) group. This probe showed rapid response (t1/2=3min), high selectivity and sensitivity for H2S with significant colorimetric and fluorescence OFF-ON signals, which was triggered by cleavage of 2,4-dinitrobenzenesulfonyl group. This probe could quantitatively detect the concentrations of H2S ranging from 0 to 60μM, and the detection of limit was found to be as low as 26nM. Cell imaging results indicated that the probe could detect and visualize H2S in the living cells.

A colorimetric and ratiometric fluorescent probe for the rapid and sensitive detection of sulfite in sugar

A colorimetric and ratiometric fluorescent probe was developed for the detection of sulfite in sugar. The probe underwent a Michael addition reaction with sulfite, which resulted in significant changes in fluorescence ratios. The probe displayed a fast response (within 30 s) and high selectivity towards sulfite over other anions and bio-thiols. The fluorescence intensity ratios were linearly related to the concentration of SO32− ranging from 0 to 15 μM, and the limit of detection was determined to be as low as 12 nM. The probe was employed to determine the concentration of sulfite in sugar with good recovery.