A novel carbazole-based mitochondria-targeted ratiometric fluorescent probe for bisulfite in living cells

A novel carbazole–indolium based mitochondria-targeted ratiometric fluorescent probe was developed, which could selectively respond to bisulfite among other sulfur-containing species in living cells.

A dual functional probe: sensitive fluorescence response to H2S and colorimetric detection for SO32−

In this study, we developed a new dual functional probe,NIR-DNP, for discriminative detection of H₂S and SO₃²⁻.

A mitochondria-targeted fluorescent probe for ratiometric detection of endogenous sulfur dioxide derivatives in cancer cells

A new mitochondria-targeted fluorescent probe HCy-D, constructed by dansyl and hemicyanine fluorophores, for SO₂derivatives (HSO₃⁻/SO₃²⁻) was presented.

An A–π–A′ structural ratiometric fluorescent probe based on benzo[e]indolium for bisulfite and its application in sugar samples and living cells

An A–π–A′ structural ratiometric fluorescent probe 1 bearing a benzo[e]indolium moiety was developed for the detection of HSO₃⁻ in PBS buffer solution.

A novel colorimetric and fluorescent iminocoumarin-based chemosensor for acetate ion and its application to living cell imaging

A novel colorimetric and fluorescent iminocoumarin-based turn-off chemosensor for acetate ion was designed and synthesized. The chemosensor could fast detect acetate ion in a 1:1 ratio within 150 ms, which could not be affected by various coexisting anions, even F(-). Futher studies showed that the detect limit was as low as 2.05×10(-7) M, and the binding constant was determined to be 1.02×10(8) M(-1). Due to these unique properties, the chemosensor showed potential application in intracellular imaging.

A solo fluorogenic probe for the real-time sensing of SO32−and SO42−/HSO4−in aqueous medium and live cells by distinct turn-on emission signals

A fluorogenic probe (L) rendered rapid and differential turn-on responses to SO₃²⁻and SO₄²⁻/HSO₄⁻in aqueous medium.

A fluorescent probe for bisulfite ions: its application to two-photon tissue imaging

Two-photon imaging of endogenous bisulphite ions of the hippocampus region of mouse brain.

A TP-FRET-based two-photon fluorescent probe for ratiometric visualization of endogenous sulfur dioxide derivatives in mitochondria of living cells and tissues

A TP-FRET-based ratiometric two-photon fluorescent probe for endogenous SO₂ derivative imaging in mitochondria has been developed for the first time.

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.

Rapidly responsive and highly selective fluorescent probe for sulfite detection in real samples and living cells

Sulfites (HSO3(-) or SO3(-)) have very significant toxicity in the environment and in the system. However, developing specific identification of sulfite probes is still very important. In this paper, a highly selective colorimetric and fluorescent probe (HHC) was synthesized to detect HSO3(-) in real samples and living cells. Sensing performance and preponderance are listed as follows. First, probe HHC showed remarkable selectivity for HSO3(-) over varieties of other species, including cysteine, glutathione, S(2-), CN(-), and reactive oxygen species, mainly because of the introduction of the electron-poor C=C double bond for HSO3(-). Second, probe HHC has great molar absorptivity, allowing it to act as a visual detection of probe for HSO3(-). Third, the fluorescence intensities of HHC linearly correlate with the concentration of HSO3(-), with a detection limit of 6.8 nm. Finally, our proposed probe can be applied to the visually determination of trace HSO3(-) in real samples and living HeLa cells with high precision. We hope that our proposed probe will greatly benefit biological sciences when biological researchers survey the role of HSO3(-) in biological systems.

Manipulating the Surface Chemistry of Quantum Dots for Sensitive Ratiometric Fluorescence Detection of Sulfur Dioxide

Herein, we report a novel approach to the rapid visual detection of gaseous sulfur dioxide (SO2) by manipulating the surface chemistry of 3-aminopropyltriethoxysilane (APTS)-modified quantum dots (QDs) using fluorescent coumarin-3-carboxylic acid (CCA) for specific reaction with SO2. The CCA molecules are attached to the surface amino groups of the QDs through electrostatic attraction, thus the fluorescence of CCA is greatly suppressed because of the formation of an ion-pair complex between the ATPS-modified QDs and CCA. Such an interaction is vulnerable to SO2 because SO2 can readily react with surface amino groups to form strong charge-transfer complexes and subsequently release the strongly fluorescent CCA molecules. The mechanism has been carefully verified through a series of control experiments. Upon exposure to different amounts of SO2, the fluorescent color of the nanoparticle-based sensor displays continuously changes from red to blue. Most importantly, the approach owns high selectivity for SO2 and a tolerance of interference, which enables the sensor to detect SO2 in a practical application. Using this fluorescence-based sensing method, we have achieved a visual detection limit of 6 ppb for gaseous SO2.

Chemical probes for molecular imaging and detection of hydrogen sulfide and reactive sulfur species in biological systems

Hydrogen sulfide (H2S), a gaseous species produced by both bacteria and higher eukaryotic organisms, including mammalian vertebrates, has attracted attention in recent years for its contributions to human health and disease. H2S has been proposed as a cytoprotectant and gasotransmitter in many tissue types, including mediating vascular tone in blood vessels as well as neuromodulation in the brain. The molecular mechanisms dictating how H2S affects cellular signaling and other physiological events remain insufficiently understood. Furthermore, the involvement of H2S in metal-binding interactions and formation of related RSS such as sulfane sulfur may contribute to other distinct signaling pathways. Owing to its widespread biological roles and unique chemical properties, H2S is an appealing target for chemical biology approaches to elucidate its production, trafficking, and downstream function. In this context, reaction-based fluorescent probes offer a versatile set of screening tools to visualize H2S pools in living systems. Three main strategies used in molecular probe development for H2S detection include azide and nitro group reduction, nucleophilic attack, and CuS precipitation. Each of these approaches exploits the strong nucleophilicity and reducing potency of H2S to achieve selectivity over other biothiols. In addition, a variety of methods have been developed for the detection of other reactive sulfur species (RSS), including sulfite and bisulfite, as well as sulfane sulfur species and related modifications such as S-nitrosothiols. Access to this growing chemical toolbox of new molecular probes for H2S and related RSS sets the stage for applying these developing technologies to probe reactive sulfur biology in living systems.

A mitochondria-targeted colorimetric and ratiometric fluorescent probe for biological SO2 derivatives in living cells

A ratiometric fluorescent probe for SO2 derivatives based on the conjugate of carbazole and indolium was presented, which could selectively respond to HSO3(-) over other thiol compounds. More importantly, CZ-Id is a novel mitochondria-targeted ratiometric fluorescent probe to image exogenous SO2 derivatives.

A simple levulinate-based ratiometric fluorescent probe for sulfite with a large emission shift

A simple 4-hydroxynaphthalimide-derived colorimetric and ratiometric fluorescent probe (1) containing a receptor of levulinate moiety was designed and synthesized to monitor sulfite. Probe 1 could quantificationally detect sulfite by a ratiometric fluorescence spectroscopy method with high selectivity and sensitivity. Specially, probe 1 exhibited a 100 nm red-shifted absorption spectrum along with the color changes from colorless to yellow, and 103 nm red-shifted emission spectra upon the addition of sulfite. Thus, 1 can serve as a "naked-eye" probe for sulfite. Further, the recognition mechanism of probe 1 for sulfite was confirmed using nuclear magnetic resonance and electrospray ionization mass spectrometry. Also, the preliminary practical application demonstrated that our proposed probe provided a promising method for the determination of sulfite.

A ratiometric fluorescent probe for rapid, sensitive and selective detection of sulfur dioxide with large Stokes shifts by single wavelength excitation

A ratiometric fluorescent probe was developed for rapid, sensitive and selective detection of SO₃²⁻ with large Stokes shifts. Imaging intracellular SO₃²⁻ was successfully demonstrated in living HNE-2 cells.

BODIPY-based colorimetric/ratiometric fluorescence probes for sulfite in aqueous solution and in living cells

Two colorimetric/ratiomrtric fluorescence probes for sulfite utilizing the Michael-addition mechanism were designed. BSP1 could be applied in the imaging of sulfite in living cells.

Colorimetric and fluorescence detection of G-quadruplex nucleic acids with a coumarin–benzothiazole probe

A colorimetric and red-emitting fluorescent dual probe for G-quadruplexes was devised with a conjugated coumarin–benzothiazole scaffold.

A twisted intramolecular charge transfer probe for rapid and specific detection of trace biological SO2 derivatives and bio-imaging applications

A highly “reactive” probe showed a ratiometric fluorescence response to HSO₃⁻ with fast response and low detection limit (3.0 nM).

A real-time colorimetric and ratiometric fluorescent probe for rapid detection of SO2 derivatives in living cells based on a near-infrared benzopyrylium dye

Near-infrared benzopyrylium dye was employed as a fast-responding ratiometric fluorescent probe for sensitive and selective detection of SO₂ derivatives in 100% aqueous solution as well as in living cells.

Selective, highly sensitive fluorescent probe for the detection of sulfur dioxide derivatives in aqueous and biological environments

On the basis of a unique nucleophilic addition reaction, a novel water-soluble broadly emitting (500-700 nm) fluorescent Probe 1 was developed for the rapid detection of SO2 derivatives in aqueous media. The positively-charged benzopyrylium moiety in Probe 1 provides both excellent water solubility, making this probe applicable in 100% aqueous environments, and the ability to function as a fluorescence quencher of the coumarin moiety. Probe 1 generates a nearly instantaneous strong fluorescence signal in response to SO2 derivatives having an 8.3 nM detection limit for bisufite. The resulting Probe 1-sulfite adduct emits in the green/red spectral region (λ(max) = 585 nm) with a large Stokes shift (139 nm). The probe exhibits excellent selectivity toward SO2 derivatives over other potential interfering agents including reactive sulfur-containing species. Importantly, we demonstrate that Probe 1 can be used for the real-time sensing and bioimaging of SO2 derivatives in living cells.

A thiazole coumarin (TC) turn-on fluorescence probe for AT-base pair detection and multipurpose applications in different biological systems

Sequence-specific recognition of DNA by small turn-on fluorescence probes is a promising tool for bioimaging, bioanalytical and biomedical applications. Here, the authors report a novel cell-permeable and red fluorescent hemicyanine-based thiazole coumarin (TC) probe for DNA recognition, nuclear staining and cell cycle analysis. TC exhibited strong fluorescence enhancement in the presence of DNA containing AT-base pairs, but did not fluoresce with GC sequences, single-stranded DNA, RNA and proteins. The fluorescence staining of HeLa S3 and HEK 293 cells by TC followed by DNase and RNase digestion studies depicted the selective staining of DNA in the nucleus over the cytoplasmic region. Fluorescence-activated cell sorting (FACS) analysis by flow cytometry demonstrated the potential application of TC in cell cycle analysis in HEK 293 cells. Metaphase chromosome and malaria parasite DNA imaging studies further confirmed the in vivo diagnostic and therapeutic applications of probe TC. Probe TC may find multiple applications in fluorescence spectroscopy, diagnostics, bioimaging and molecular and cell biology.

Determination of gaseous sulfur dioxide and its derivatives via fluorescence enhancement based on cyanine dye functionalized carbon nanodots

The development of convenient methods for sulfur dioxide and its derivatives analysis is critically important because SO2 causes worldwide serious environmental problems and human diseases. In this work, we show an unprecedented example of an energy-transfer-based fluorescence nanoprobe for selective and quantitative detection of SO2, through molecular engineering of the fluorescent carbon nanodots by a cyanine dye which have a unique reactivity to bisulfite, achieving a detection limit of 1.8 μM with a linear relationship (R(2) = 0.9987). The specific detection was not interfered with other potential coexisted species. In addition, the probe is demonstrated for the determination of SO2 gas in aqueous solution as well as for visually monitoring of SO2 gas in air. This nanomaterial based probe is easily prepared, fast responding, and thus potentially attractive for extensive application for the determination of SO2 and other similar air pollutants.

A ratiometric fluorescent probe based on a coumarin-hemicyanine scaffold for sensitive and selective detection of endogenous peroxynitrite

In the study described herein, the red emitting probe CHCN, which possesses a linked coumarin-hemicyanine scaffold, was developed for detection of peroxynitrite (ONOO(-)) under physiological conditions. The studies show that CHCN displays a dual ratiometric and colorimetric response to ONOO(-) that is caused by an oxidation process. A possible mechanism of this oxidation process was proposed and confirmed by ESI-MS spectra for the first time. CHCN shown highly selective and sensitive towards ONOO(-) with a low limit of detection LOD (49.7 nM). Moreover, CHCN has appreciable cell permeability and, as a result, it is applicable to ratiometric detection of exogenous and endogenous ONOO(-) in living cells during phagocytic immune response. We anticipate that, owing to their ideal properties, probes of this type will find great use in explorations of the role played by ONOO(-) in biology.

Development of a new colorimetric and red-emitting fluorescent dual probe for G-quadruplex nucleic acids

A tailor-made colorimetric and red-emitting fluorescent dual probe for G-quadruplex nucleic acids was developed by incorporating a coumarin-hemicyanine fluorophore into an isaindigotone framework. The significant and distinct changes in both the color and fluorescence of this probe enable the label-free and visual detection of G-quadruplex structures.

Ratiometric fluorescent probe for rapid detection of bisulfite through 1,4-addition reaction in aqueous solution

A ratiometric fluorescent probe based on a positively charged benzo[e]indolium moiety for bisulfite is reported. The bisulfite underwent a 1,4-addition reaction with the C-4 atom in the ethylene group. This reaction resulted in a large emission wavelength shift (Δλ = 106 nm) and an observable fluorescent color change from orange to cyan. The reaction could be completed in 90 s in a PBS buffer solution and displayed high selectivity and sensitivity for bisulfite. A simple paper test strip system was developed to detect bisulfite rapidly. Probe 1 was used to detect bisulfite in real samples with good recovery.

Fluorescent probes for hydrogen sulfide detection and bioimaging

In this feature article, we address the synthesis and design strategies for the development of fluorescent probes for H₂S, based on the reaction type between H₂S and the probes.

Simultaneous fluorescence sensing of Cys and GSH from different emission channels

A chlorinated coumarin-hemicyanine dye with three potential reaction sites was exploited as fluorescent probe for biothiols. The Cys-induced substitution-rearrangement-cyclization, Hcy-induced substitution-rearrangement, and GSH-induced substitution-cyclizatioin cascades lead to the corresponding amino-coumarin, amino-coumarin-hemicyanine, thiol-coumarin with distinct photophysical properties, enabling Cys and GSH to be selectively detected from different emission channels at two different excitation wavelengths.