Delayed rectifier potassium channels are involved in SO2 derivative-induced hippocampal neuronal injury

An efficient dual-function fluorescent probe for sulfites and sulfides and its imaging application in cells

As gas signaling molecules in organisms, SO2 derivatives and H2S play crucial regulating roles in a series of physiological processes. Therefore, developing an assay that can accurately monitor the concentration of SO2 derivatives and H2S in cells is extremely important for the research and treatment of related illnesses. A bifunctional probe SN-F based on FRET mechanism for SO2 derivatives and H2S was designed. SN-F had a short response time to SO2 (2 min), excellent anti-interference capability and selectivity in the non-organic solvent system (pH = 7.4), which was suitable for the determination of SO2 derivatives in cells. SN-F had a wide linear range for H2S. Moreover, SN-F was applied in cell imaging successfully with high targeting ability to endoplasmic reticulum (ER) and could monitor endogenous and exogenous H2S in cells.

A rationally designed fluorescent probe for sulfur dioxide and its derivatives: applications in food analysis and bioimaging

Exogenous sulfur dioxide (SO2) and its derivatives (SO32-/HSO3-) have been extensively utilized in food preservation and endogenous SO2 is recognized as a significant gaseous signaling molecule that can mediate various physiological processes. Overproduction and/or extensive intake of these species can trigger allergic reactions and even tissue damage. Therefore, it is highly desirable to monitor SO2 and its derivatives effectively and quantitatively both in vitro and in vivo. Herein, a new mitochondria-targeted fluorescent probe (PIB) had been constructed, which could ratiometrically recognize SO2 and its derivatives with excellent sensitivity (DL = 15.9 nM) and a fast response time (200 s). The obtained high selectivity and good adaptability of this SO2-specific probe in a wide pH range (6.5-10.0) allowed for quantitatively tracking of SO2 and its derivatives in real food samples (granulated sugar, crystal sugar, and white wine). In addition, PIB could locate at mitochondrion and was capable of imaging exogenous/endogenous SO2 in the cells and zebrafish. In particular, our findings represented one of the rare examples that have demonstrated endogenous SO2 is closely related with the apoptosis of cells. Importantly, probe PIB was successfully employed for in situ metabolic localization in mouse organs, implying the potential applications of our probe in further exploration on SO2-releated pathological and physiological processes.

Structure-regulated mitochondrial-targeted fluorescent probe for sensing and imaging SO2in vivo

SO2 and its derivatives play an important role in the antioxidation and anticorrosion of food and medicine. In biological systems, abnormal levels of SO2 lead to the occurrence of many biological diseases. Hence, the development of suitable tools for monitoring SO2 in mitochondria is beneficial for studying the biological effect of SO2 in subcellular organelles. In this research, DHX-1 and DHX-2 are fluorescent probes designed on the basis of dihydroxanthene skeletons. Importantly, DHX-1 (650 nm) and DHX-2 (748 nm) show near-infrared fluorescence response toward endogenous and exogenous SO2, which showed advantages of great selectivity, good sensitivity and low cytotoxicity, and the detection limit is 5.6 μM and 4.08 μM of SO2, respectively. Moreover, DHX-1 and DHX-2 realized SO2 sensing in HeLa cells and zebrafish. Moreover, cell imaging demonstrated that DHX-2 with a thiazole salt structure possesses good mitochondria-targeting ability. Additionally, DHX-2 was perfectly achieved by in situ imaging of SO2 in mice.

A FRET-based ratiometric fluorescent probe for SO32- detection in Chinese medicine and living cells

Chinese herbal medicine is receiving more and more attention at home and abroad as a traditional Chinese clinical medicine. To make herbal medicines can be preserved for a long time, they are usually fumigated with sulfur. However, after the medicinal materials have been fumigated with sulfur, SO₂ residues will remain, which, when exposed to water, will create sulfites and bisulfites. Excessive sulfites can cause a variety of severe ailments and diminish the quality and effectiveness of therapeutic plants. Therefore, developing an effective SO₃^2-/HSO₃^- detection method is important. This study chose coumarin derivatives as fluorescent acceptors and pyridinium acrylonitrile structures as fluorescent donors to create a ratiometric fluorescent probe CPA using the fluorescence resonance energy transfer (FRET) effect. The probe CPA exhibited a fluorescence transition from red to green under excitation at 405 nm with an interval of 149 nm, a reaction time of less than 1 min, a low detection limit of 86 nM, and the probe CPA has good specific recognition of SO₃^2- and is resistant to interference. In addition, CPA has low in vitro cytotoxicity and can successfully detect endogenous sulfites in living cells.

A red fluorescence probe for reversible detection of HSO3-/H2O2 and its application in food samples and bioimaging

Reducing agent SO₂ and oxidant H₂O₂ are two essential substances in cells, and the balance between them is closely related to the survival of cells. SO₂ derivative HSO₃^- is often used as food additive. Therefore, simultaneous detection of SO₂ and H₂O₂ is of great significance in biology and food safety. In this work, we successfully developed a mitochondria-targeted red fluorescent probe (HBTI), which has excellent selectivity, high sensitivity and large Stokes shift (202 nm). HBTI and HSO₃^-/SO₃^2- undergo Michael addition on the unsaturated C=C bond, and the addition product (HBTI-HSO₃^-) can react with H₂O₂ to restore the conjugated structure. Fluorescence changes from red to non-emissive and then restores to red, and can be detected quickly and visually. In addition, HBTI has been successfully targeted mitochondria, and achieved dynamic reversible response to SO₂/H₂O₂ in living cells, and has been successfully applied to detect SO₂ in food samples.

Aryl-Phenanthro[9,10-d]imidazole: A Versatile Scaffold for the Design of Optical-Based Sensors

Fluorescent and colorimetric sensors are important tools for investigating the chemical compositions of different matrices, including foods, environmental samples, and water. The high sensitivity, low interference, and low detection limits of these sensors have inspired scientists to investigate this class of sensing molecules for ion and molecule detection. Several examples of fluorescent and colorimetric sensors have been described in the literature; this Review focuses particularly on phenanthro[9,10-d]imidazoles. Different strategies have been developed for obtaining phenanthro[9,10-d]imidazoles, which enable modification of their optical properties upon interaction with specific analytes. These sensing responses usually involve changes in the fluorescence intensity and/or color arising from processes like photoinduced electron transfer, intramolecular charge transfer, intramolecular proton transfer in the excited state, and Förster resonance energy transfer. In this Review, we categorized these sensors into two different groups: those bearing formyl groups and their derivatives and those based on other molecular groups. The different optical responses of phenanthro[9,10-d]imidazole-based sensors upon interaction with specific analytes are discussed.

Mitochondria-targetable colorimetric and far-red fluorescent sensor for rapid detection of SO2 derivatives in food samples and living cells

Sulfur dioxide (SO₂) derivatives are intertwined with many physiological and pathological processes in living systems, and excess intake of them are associated with various diseases. Herein, we have rationally constructed a novel colorimetric and far-red fluorescent probe for HSO₃^- based on a rhodamine analogue skeleton bearing a 3-quinolinium carboxaldehyde moiety. The novel probe exhibited a significant far-red fluorescence "Turn-on" response to HSO₃^-, along with obvious color change from reddish to purple via the specific 1,4-nucleophilic addition reaction of HSO₃^- with the quinolinium moiety in 3-(4-(2-carboxyphenyl)-7-(diethylamino)chromenylium-2-yl)-1-methylquinolin-1-ium hypochlorite trifluoromethanesulfonate (AQCB). The AQCB had excellent water-solubility, and presented rapid response (<15 s),highsensibility(LOD = 49 nM) and selectivity toward HSO₃^-. In addition, the probe was able to detect the content of HSO₃^- in food samples with satisfactory results. Furthermore, the probe possessed good cell membrane and could be successfully applied for imaging HSO₃^- in the mitochondria of living cells.

Mitochondria-targeted and FRET-based fluorescent probe for the imaging of endogenous SO2 in living cells

Sulfur dioxide (SO₂) is an important signal molecule in living systems, and plays a wide range of physiological functions. Real-time and in situ detection of the dynamic balance of SO₂ in mitochondria is of great significance to in-depth study its biological roles. Herein, we have developed a mitochondria-targeted fluorescent probe Nap-L based on the FRET mechanism to detect SO₂ in living cells. The probe Nap-L employed naphthalimide and positively charged benzopyridine as the donor and acceptor in the FRET system, and emitted green and red fluorescence under excitation. In respond to SO₂, the nucleophilic addition of bisulfite to benzopyridine and then interrupted the FRET process from naphthalimide to benzopyridine fluorophore, thereby triggering an obvious change in the fluorescence ratio. The probe Nap-L showed high selectivity to SO₂ over the biothiols (Hcy, GSH, Cys) and other biologically related species. Biological experiments suggested that the probe Nap-L mainly distributed in mitochondria, and can be successfully used to detect mitochondrial endogenous SO₂ in living cells.

A novel fluorescent probe for the detection of sulfur dioxide derivatives and its application in biological imaging

A new probe CA-SO2 to efficiently and specifically detect SO2 was designed. The probe showed a fast response time (<50 s), low detection limit (LOD = 75 nM), large Stokes shift (129 nm) and was applied to detect SO2 in living cells and zebrafish.

A FRET-based ratiometric fluorescent probe to detect cysteine metabolism in mitochondria

As an important biothiol in living cells, cysteine is closely related to oxidative damage in living organisms. Sulfite from cysteine metabolism in living cells plays a crucial role in maintaining homeostasis in an organism, and the unbalance of sulfite in vivo would lead to multiple diseases. Thus the development of a new fluorescent probe for cysteine metabolism is needed urgently in mitochondria which are the main place of cysteine metabolism. Herein we construct a novel targeting mitochondria fluorescent probe CP-K based on the FRET mechanism to visualize sulfite in living MCF-7 cells. Probe CP-K displays a large Stokes shift of 150 nm, a low detection limit (26.3 nM) and "naked eye" detection after the addition of HSO3-. Importantly, it is appropriate for imaging the endogenous sulfite from cysteine metabolism in living cells.

Recent progress in the small-molecule fluorescent probes for the detection of sulfur dioxide derivatives (HSO3-/SO32-)

Sulfur dioxide (SO₂) had been recognized as an environmental pollutant produced from industrial processes. SO₂ is water soluble and forms hydrated SO₂ (SO₂·H₂O), bisulfite ion (HSO₃^-), and sulfite ion (SO₃^2-) upon dissolution in water. SO₂ could be also produced endogenously from sulfur-containing amino acids l-cysteine in mammals. Endogenous SO₂ can maintain the balance of biological sulfur and redox equilibrium in vivo, regulate blood insulin levels and reduce blood pressure. Excess intake of exogenous SO₂ can result in respiratory diseases, cardiovascular diseases and neurological disorders. As a result, fluorescent probes to detect HSO₃^-/SO₃^2- have attracted great attention in recent years. Herein, a general overview was provided with the aim to highlight the typical examples of the HSO₃^-/SO₃^2- fluorescent probes reported since 2010, especially those in the past five years. We have classified HSO₃^-/SO₃^2- fluorescent probes through different chemical reaction mechanisms and wish this review will give some help to the researchers in this field.

A Fluorescently Ratiometric Natural Probe for Selective Detection of Sulfur Dioxide Derivative and Host-Guest Supramolecular Regulation

Natural sanguinarine (SG) was first used as a fluorescent probe to develop a novel ratiometric sensor for selective HSO₃^- detection. The nucleophilic addition reaction of HSO₃^- occurs at the C=N⁺ group of SG, and subsequent breakage of the conjugated π cycle leads to a decrease in the SG iminium fluorescence that is accompanied by an increase in the alkanolamine fluorescence. Therefore, a ratiometric fluorescence method with a large wavelength shift can be established for HSO₃^- detection. Furthermore, cucurbit[8]uril was used as an efficient host to encapsulate SG for an improved selectivity for HSO₃^- detection over H₂S. Our method benefits include little interference from other common anions and cations for HSO₃^- detection, suggesting a promising application in real sample analysis. Besides sensor development, the interaction of the natural SG with HSO₃^- was first demonstrated in this work to further get an insight into SG's pharmacology.

A novel colorimetric and ratiometric fluorescent probe for sensing SO2 derivatives and their bio-imaging in living cells

We report a novel fluorescent probe HBN-TCF for the detection of SO2 derivatives. This probe exhibited near-infrared fluorescence emission with an excitation wavelength of 620 nm. After reacting with SO32-, the emission channel at 664 nm decreased, while the new strong emission channel at 482 nm increased (λex = 400 nm), with a large emission distance (Δλ = 182 nm) observed. This probe exhibited the rapid and selective detection of SO2 derivatives compared with other sulfur-containing species and featured a low detection limit (82 nM). This colorimetric and ratiometric fluorescent probe showed high selectivity and sensitivity for detecting SO2 derivatives. The probe was also successfully exploited for the fluorescence imaging of intracellular and exogenous SO2 derivatives in BEL-7402 cells.

Sulfur dioxide induces apoptosis via reactive oxygen species generation in rat cardiomyocytes

Epidemiological evidence suggests that the incidence and mortality of cardiovascular diseases are closely related to sulfur dioxide (SO₂). In the present study, H9C2 cells were incubated with 100 μM NaHSO₃ with or without pretreatment of an antioxidant, N-acetyl-L-cysteine (NAC). The changes of apoptosis rate, mitochondrial membrane potential (MMP), ATP content, caspase-3 activity, and reactive oxygen species (ROS) were detected. Rats were inhaled 7 mg/m³ SO₂ and/or intraperitoneal injected with 50 mg/kg (bw) of NAC for 30 days. RT-PCR and Western blot were used to detect the mRNA and protein levels of apoptosis-related genes. We found that the apoptosis of H9C2 cells was induced by NaHSO₃, which decreased the content of MMP and ATP, and induced the expression of caspase-3. NAC can inhibit the apoptosis induced by NaHSO₃ treatment. SO₂ and NaHSO₃ decreased the expression of Bcl-2 and the ratio of Bcl-2/Bax, increased the expression of Bax and P53 accumulation and phosphorylation, and activated caspase-9 and caspase-3. Whereas NAC can reduce the changes of apoptosis-related proteins in rat heart. Our results suggest that SO₂ induces ROS-mediated P53 and caspase-dependent mitochondrial signaling pathways in H9C2 cells and rat hearts. Antioxidant therapy can reduce the adverse reactions of SO₂ and lead to a decline in the cardiovascular disease induced by SO₂.

A real-time ratiometric fluorescent probe for imaging of SO2 derivatives in mitochondria of living cells

A real-time ratiometric fluorescent probe (IN-CZ) for highly selective detection of sulfite was designed and synthesized, which is based on modulating the intramolecular charge transfer (ICT) of the hemicyanine dye platform. The mechanism of using the probe is mainly through the Michael addition that occurs between IN-CZ and sulfite with a detection limit of 2.99 × 10⁻⁵ M. IN-CZ displays a fast response (within 1 minute) and is highly selective for SO₃²⁻/HSO₃⁻ over ROS, biologically relevant ions, biological mercaptans and other reactive species. More importantly, IN-CZ was suitable for ratiometric fluorescence imaging in living cells, by real-time monitoring of SO₃²⁻/HSO₃⁻ changes in mitochondria targeted in living cells.

A real-time ratiometric fluorescent probe (IN-CZ) for highly selective detection of sulfite was designed and synthesized, which is based on modulating the intramolecular charge transfer of the hemicyanine dye platform.

Mitochondrial directed ratiometric fluorescent probe for quantitive detection of sulfur dioxide derivatives

A good biocompatibility fluorescence probe for imaging of sulfur dioxide derivatives in cancer cells.

A near-infrared and two-photon dual-mode fluorescent probe for the colorimetric monitoring of SO2in vitro and in vivo

A near-infrared and two-photon dual-mode fluorescent CY probe was developed for the colorimetric monitoring of SO₂in vitro and in vivo.

A new ratiometric fluorescence assay based on resonance energy transfer between biomass quantum dots and organic dye for the detection of sulfur dioxide derivatives

Sulfur dioxide (SO₂) is considered as the fourth gas signal molecule after nitric oxide (NO), carbon monoxide (CO) and hydrogen sulfide (H₂S). It plays important roles in several physiological processes. Therefore, the design and synthesis of nanoprobes for the detection of SO₂ derivatives in cells is of great significance. Herein, we report a new ratiometric fluorescence nanoprobe based on resonance energy transfer (RET) between biomass quantum dots (BQDs) and organic dye (DMI) for the detection of SO₂ derivatives. The proposed ratiometric fluorescence assay allows the determination of HSO₃⁻ in the range of 1.0 to 225 μM with a detection limit of 0.5 μM. Importantly, the proposed ratiometric fluorescence nanoprobe exhibits a high photostability and good selectivity for HSO₃⁻ over other chemical species including H₂S and biological mercaptans. Quantitation of HSO₃⁻ in cell lysates by using the nanoprobe is demonstrated.

A new ratiometric fluorescence assay has been developed for the detection of sulfur dioxide derivatives with repeatability and selectivity. The assay was applied to quantitate HSO₃⁻ in cell lysates with accurate results.

A ratiometric fluorogenic probe for the real-time detection of SO32- in aqueous medium: application in a cellulose paper based device and potential to sense SO32- in mitochondria

A new water soluble and fluorogenic probe (L) that can demonstrate a specific ratiometric detection of a SO₂ derivative (SO₃^2-) in 100% aqueous medium and live cells has been designed and synthesized. The detection process can be visualized by the naked eye, as the orange-red fluorescence of L turns into a strong blue fluorescence upon interaction with SO₃^2-. L displayed several beneficial attributes such as detection in complete aqueous medium, extremely fast response time along with high selectivity and sensitivity. The ratiometric sensing was attributed to the selective nucleophilic addition reaction of SO₃^2- with L. The probe was further used to develop a low cost microfluidic sensor device (μPAD). The probe was biocompatible and its potential to sense SO₃^2- in mitochondria was captured in live HeLa cells.

A Novel Colorimetric Fluorescent Probe for SO₂ and Its Application in Living Cells Imaging

A novel chromenylium-based fluorescent probe was exploited for sulphur dioxide (SO₂) detecting. The probe displayed a remarkable fluorescence turn-on response towards SO₂ based on the nucleophilic addition reaction to the carbon-carbon double bond with 105 nm Stock shift. The probe was successfully applied for the quantification of SO₂.The linear detection range was from 0-160 μM with the detection limit as low as 99.27 nM. It also exhibited high selectivity for SO₂ than other reactive species and amino acids. Furthermore, cell staining experiments indicated that the probe was cell membrane permeable and could be used for high-performance imaging of SO₂ in living cells. The superior properties of the probe made it highly promising for use in chemical and biological applications.

A Novel Approach of Weighted Support Vector Machine with Applied Chance Theory for Forecasting Air Pollution Phenomenon in Egypt

The particulate matter air pollutant of diameter less than 10 micrometers (PM[Formula: see text]), a category of pollutants including solid and liquid particles, can be a health hazard for several reasons: it can harm lung tissues and throat, aggravate asthma and increase respiratory illness. Accurate prediction models of PM[Formula: see text] concentrations are essential for proper management, control, and making public warning strategies. Therefore, machine learning techniques have the capability to develop methods or tools that can be used to discover unseen patterns from given data to solve a particular task or problem. The chance theory has advanced concepts pertinent to treat cases where both randomness and fuzziness play simultaneous roles at one time. The main objective is to study the modification of a single machine learning algorithm — support vector machine (SVM) — applying the chance weight of the target variable, based on the chance theory, to the corresponding dataset point to be superior to the ensemble machine learning algorithms. The results of this study are outperforming of the SVM algorithms when modifying and combining with the right theory/technique, especially the chance theory over other modern ensemble learning algorithms.

Air Pollution Forecasting Model Based on Chance Theory and Intelligent Techniques

A novel approach of weighted support vector regression (WSVR) technique with applied chance theory was proposed to build a robust forecasting model, called the chance weighted support vector regression (chWSVR) model. In order to forecast the particulate matter air pollutant of diameter less than 10 micrometers (PM10) one hour advance in the Greater Cairo Metropolitan Area (GCMA) in Egypt. The chance theory has advanced concepts pertinent to treat cases where both randomness and fuzziness play simultaneous roles at one time. The basic idea based on the proposed chWSVR model is assigning the chance weight value of the target variable, based on the chance theory, to its corresponding dataset point to become minimized in the objective function making that point more significant during the training process. Measuring data were collected and reprocessed from four monitoring stations located in GCMA and relative to the springs during the period from 2007 to 2010. The results of such model compared to similar ones built by other machine learning techniques, Random Forest and Bootstrap aggregating techniques. In all stations, comparing such models revealed that the proposed chWSVR model findings were promising in the forecasting of PM10 hourly concentration.

A series of water-soluble A-π-A' typological indolium derivatives with two-photon properties for rapidly detecting HSO3 -/SO3 2- in living cells

It is believed that HSO₃ ^- and SO₃ ^2- play important roles in several physiological processes. However, probes with two-photon absorption to detect HSO₃ ^- or SO₃ ^2- in living cells are still limited. Herein, a series of novel indolium derivatives (L1-L4) with an A-π-A' structure was designed and synthesized as ratiometric probes to detect HSO₃ ^-/SO₃ ^2-in vitro. L3 and L4 display a colorimetric and ratiometric fluorescence dual response to HSO₃ ^-/SO₃ ^2- with a very fast (∼15 s) and high specificity, as well as low detection limits (∼22 nM). Furthermore, their detection is also carried out by using a two-photon excited fluorescence method. A nucleophilic addition reaction is proposed for the sensing mechanism, which is supported by MS, ¹H NMR, and density functional theory (DFT) investigations. Importantly, L3 was successfully used for detecting intrinsically generated intracellular HSO₃ ^-/SO₃ ^2- in cancerous cells under one- and two-photon excited fluorescence imaging.

A novel ratiometric fluorescent probe for selective detection of bisulfite in living cells

In this work, a new type of ratiometric fluorescent probe APCT for bisulfite anion based on Michael-type addition reaction was designed.

Synergistic effects of particulate matter (PM2.5) and sulfur dioxide (SO2) on neurodegeneration via the microRNA-mediated regulation of tau phosphorylation

Because air pollution is a complex mixture of pollutants consisting of both particulate and gaseous components, understanding the health risks from these pollutants requires an evaluation of their combined effects rather than predictions based on the toxicities of single chemicals alone. Particulate matter (PM2.5) and sulfur dioxide (SO2) commonly co-exist in the atmospheric environment, and epidemiological studies have linked air pollution to the development of neurodegenerative disorders, in addition to increased morbidity from cardiopulmonary diseases. However, few studies have examined the potential effects from combinations of these pollutants on neurodegeneration, especially at NOEC doses. In the present study, we first found that PM2.5 and SO2 co-exposure leads to neurodegeneration at low doses, including neuronal apoptosis, the reduction of synaptic structural protein postsynaptic density (PSD-95) and synaptic functional protein N-methyl-d-aspartate (NMDA) receptor subunits (NR2B), and the elevation of tau phosphorylation in vitro and in vivo, which did not induce clear effects when the compounds were tested separately. Furthermore, we clarified that the microRNA (miRNA) miR-337-5p, which is homologous to a human miRNA that targets tau, was involved in the combined effect and contributed to synergistic neurodegeneration. This work implies the potential risk of neuronal dysfunction from the co-existence of PM2.5 and SO2 in coal-burning areas and provides new insights into the molecular markers for the relevant diseases.

A ratiometric fluorescence probe for selective detection of sulfite and its application in realistic samples

A new fluorescent probe 7-(diethylamino)-3-((1e,3e)-5-oxo-5-phenylpenta-1,3-dien-1-yl)-2H-chromen-2-one (SPH), based on Michael addition mechanism, was designed and synthesized for selective detection of sulfite. The probe was constructed by incorporating an α,β-unsaturated ketone conjugated with a C˭C bond into the coumarin fluorophore as a specifical reaction site for sulfite utilizing its nucleophilic property. The extra conjugated C˭C bond induced obvious red-shifts in both absorption and emission maxima, and remarkably promoted the nucleophilic addition rate. Once treated with sulfite, the solution's color changed from orange to yellow companied with a strong blue-green fluorescence. The ratio of fluorescence intensity at 488nm and 630nm (I₄₈₈/I₆₃₀) was linear with sulfite concentration over the range of 0-80μM with a detection limit of 0.23μM. High selectivity and good competition of the probe toward sulfite over other anions and thiols enable us to monitor sulfite levels in realistic samples as well as in living HeLa cells.

A two-photon fluorescent turn-on probe for imaging of SO2 derivatives in living cells and tissues

SO2 and its derivatives (bisulfite/sulfite) play crucial roles in several physiological processes. Therefore, development of reliable analytical methods for monitoring SO2 and its derivatives in biological systems is very significant. In this paper, a FRET-based two-photon fluorescent turn-on probe, A-HCy, was proposed for specific detection of SO2 derivatives through the bisulfite/sulfite-promoted Michael addition reaction. In this FRET system, an acedan (2-acetyl-6-dialkylaminonaphthalene) moiety was selected as a two-photon donor and a hemicyanine derivative served as both the quencher and the recognition unit for bisulfite/sulfite. A-HCy exhibited excellent selectivity and rapid response to HSO3(-) with a detection limit of 0.24 μM. More importantly, probe A-HCy was first successfully applied in two-photon fluorescence imaging of biological SO2 derivatives in living cells and tissues, suggesting its great potential for practical application in biological systems.

A water-soluble and fast-response mitochondria-targeted fluorescent probe for colorimetric and ratiometric sensing of endogenously generated SO2 derivatives in living cells

A novel water-soluble mitochondria-targeted ratiometric fluorescent probe (Cl-2) is presented. Cl-2 can respond selectively to SO2 derivatives within 1 min. Notably, Cl-2 can be used to monitor successfully the concentration change of endogenously generated SO2 derivatives in living cells.

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 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.