A New Red-Emitting Fluorescence Probe for Rapid and Effective Visualization of Bisulfite in Food Samples and Live Animals

Fluorescence based metabisulfite sensing: New aspects of ion sensing by a styryl benzothiazolium dye and understanding nitrite interference

Detection of specific ions using fluorescent probes has relevance in several areas of therapeutics development and environmental science. Here, we provide new perspectives to the sensing of a styryl benzothiazolium-based fluorescent compound 1 and report that sensing properties are for sulfite ions in general with highest preference for metabisulfite ions (S2O52-) adding to its previously determined role as a bisulfite ion sensor. This probe exhibits its sensing action via an addition reaction in which the styryl double bond gets reduced. The interference studies highlighted that the sequence of addition of nitrite and metabisulfite has a bearing on the overall interference outcome. Spectroscopic studies revealed that the order of preferential sensing of sulfites and sulfide ion is S2O52- > HSO3- > SO32- > S2-. Although this probe displays robust sensing on its own through fluorescence quenching, its fluorescence emission can be enhanced at much lower concentrations in the presence of a G-quadruplex DNA without compromising the outcome of the sensing.

A fluorescent probe with serum albumin as a signal amplifier for real-time sensing of HSO3- in solution, mitochondria of animal cells and rice roots

Endogenous release of HSO3- during the enzymatic oxidation of sulfur containing amino acids in mitochondria or insufficiency of sulfite oxidase results in the accumulation of sulfite and thiosulfate in biological fluids affecting mitochondrial homeostasis of brain mitochondria associated with serious clinical symptoms related to neurological disorders. The red fluorescent probe MGQ undergoes self-assembly in water and reveals aggregation induced quenching of fluorescence. MGQ reveals 143-fold and 179-fold increases in fluorescence intensity at 645 nm, respectively, in the presence of HSA and BSA and does not significantly differentiate between two albumins. The detailed studies of MGQ have been performed in the presence of BSA. The presence of other enzymes/proteins and amino acids, viz. pepsin, trypsin, lysozyme, Bromelain, lysine, histidine, hemoglobin, etc., does not affect the fluorescence of MGQ or MGQ-BSA solutions and points to high selectivity towards BSA. The limit of detection for BSA is 10 nM. In PBS buffer, MGQ in the absence of BSA does not react with HSO3- and sluggishly in a 1 : 1 ethanol-water mixture. However, in the confined space of BSA/HSA, MGQ displays a signal amplification, undergoes instantaneous Michael type addition of HSO3- and results in a ratiometric change in fluorescence intensity in ≤1.5 min with the decrease of red fluorescence at 645 nm and emergence of green fluorescence at 515 nm. The LOD for the detection of HSO3- is 4 nM.

An innovative dual-organelle targeting NIR fluorescence probe for detecting hydroxyl radicals in biosystem and inflammation models

The hydroxyl radical (OH) is highly reactive and plays a significant role in a number of physiological and pathological processes within biosystems. Aberrant changes in the level of hydroxyl radical are associated with many disorders including tumor, inflammatory and cardiovascular diseases. Thus, detecting reactive oxygen species (ROS) in biological systems and imaging them is highly significant. In this work, a novel fluorescent probe (HR-DL) has been developed, targeting two organelles simultaneously. The probe is based on a coumarin-quinoline structure and exhibits high selectivity and sensitivity towards hydroxyl radicals (OH). When reacting with OH, the hydrogen abstraction process released its long-range π-conjugation and ICT processes, leading to a substantial red-shift in wavelength. This probe has the benefits of good water solubility (in its oxidative state), short response time (within 10 s), and unique dual lysosome/mitochondria targeting capabilities. It has been applied for sensing OH in biosystem and inflammation mice models.

A dual-functional NIR fluorescence probe for detecting hypochlorous acid and bisulfite in biosystem

BACKGROUND

Bisulfite (HSO3-) serves as a bleaching agent, antioxidant, antimicrobial, and regulator of enzymatic reactions in biosystem. However, abnormal levels of bisulfite can be detrimental to health. Hypochlorous acid (HOCl), which acts as bioactive small molecules, is crucial for maintaining normal biological functions in living organisms. Disruption of its equilibrium can lead to oxidative stress and various diseases. Therefore, it's essential to monitor the fluctuations of HOCl and HSO3- at cellular and in vivo levels to study their physiological and pathological functions.

RESULTS

This study constructed a novel NIR bifunctional colorimetric fluorescent probe using thienocoumarin-indanedione structures to identify hypochlorite (ClO-) and bisulfite (HSO3-). By using CSO-IO to recognize HSO3- and HOCl, two distinct products were generated, displaying green and blue fluorescence, respectively. This property effectively allows for the simultaneous dual-functional detection of HSO3- (LOD: 113 nM) and HOCl (LOD: 43 nM).

SIGNIFICANCE

In this work, the biocompatible molecule CSO-IO has been effectively designed to detect HOCl/HSO3- in living cells and zebrafish. As a result, the dual-functional fluorescent probe has the potential to be utilized as a molecular tool to detect HSO3- derived compounds and HOCl simultaneously within the complex biological system.

A ratiometric fluorescence probe for bisulfite detection in live cells and meat samples

The development of reliable probe technology for the detection of bisulfite (HSO3-) in situ in food and biological samples is contributing significantly to food quality and safety assurance as well as community health. In this work, a responsive probe, EHDI, is developed for ratiometric fluorescence detection of HSO3- in aqueous solution, meat samples, and living cells. The probe is designed based on the HSO3- triggered 1,4-addition of electron deficit C = C bond of EHDI. As a result of this specific 1,4-addition, the π-conjugation system was destructed, resulting in blue shifts of the emission from 687 to 440 nm and absorption from 577 to 355 nm. The probe has good water solubility, high sensitivity and selectivity, allowing it to be used for imaging of HSO3- internalization and production endogenously. The capability of probe EHDI for HSO3- was then validated by traditional HPLC technology, enabling accurately detect HSO3- in beef samples. The successful development of this probe thus offers a new tool for investigating HSO3- in situ in food and biological conditions.

Taming Janus-Faced Quinoline-Derived Fluorescent Probes for Dual-Channel Distinguishable Visualization of HSO3- and HClO in Dried Foods and Living Cells

With the booming development of food manufacturing, developing ideal analytical tools to precisely quantify food additives is highly sought after in the food science field. Herein, a new series of quinoline-derived multifunctional fluorescent probes has been synthesized. Bearing double reactive sites, these compounds display fluorescence response toward both bisulfite (HSO3-) and hypochlorous acid (HClO). Among these compact structures, compound ethyl-2-cyano-3-(6-(methylthio)quinolin-2-yl)acrylate (QTE) was screened out. Probe QTE not only shows ratiometric variation toward HSO3- with little cross talk but also performs turn-off signal toward HClO. In addition, probe QTE has been utilized for bioimaging of HClO in living cells. Furthermore, the HSO3- content in dried food samples has been appraised by QTE with satisfactory results. Meanwhile, relying on the apparent chromaticity change, a flexible dark-box device has been elaborated for chromatic analysis, promoting visualization of HSO3- in the field.

A near-infrared fluorescent probe for rapid and on-site detection of sulfur dioxide derivative in biological, food and environmental systems

Emission of toxic gaseous sulfur dioxide (SO2) and its derivative bisulfite (HSO3-) from various industrial applications, like food processing, transportation, and the coking process, has raised substantial concerns regarding environmental quality and public health. The probes for specific and sensitive detection of SO2 derivatives plays an essential role in their regulation, and ultimately mitigating their environmental and health implications, but the one that can detect SO2 derivatives onsite by end users remains limited. Herein, we report a new near-infrared fluorescence probe (SL) for rapid and onsite detection of SO2 derivative, HSO3- in industrial wastewater, food samples and for sensing its interaction with biological organisms. The SL is developed through coupling of quinolinium and coumarin moiety through an electron deficit CC bond that can specifically react with HSO3- via a Michael addition. By recording the blue shift of absorption and emission spectra, SL can sensitively detect HSO3- (limit of detection, 38 nM) in aqueous solution within 40 s SL is biocompatible, can be used for evaluating toxicity of SO2 derivatives in living organisms. The preparation of SL-stained test paper allows the colorimetric/fluorometric analysis for quantification of HSO3- onsite in food, river and coking wastewater samples using a smartphone. The successful development of SL not only provides a new tool to investigate HSO3- in biological, food and environmental systems, but also potentially promotes the application of fluorescence technique for rapid and onsite analysis of real-world samples by end users.

A near infrared fluorescence probe with dual-site for hydrogen sulfide and sulfur dioxide detection

Both hydrogen sulfide (H2S) and sulfur dioxide (SO2) are regarded as double-edged swords. They are toxic gases at high concentration, and at low concentration they are beneficial to the human. Therefore, it is of great significance to develop single chemosensor which enable to detect them with different fluorescence signal changes. In this work, a novel dual-site fluorescence probe (AMN-SSPy) with near infrared emission (675 nm) was designed, which realized quantitative detection for H2S and SO2 by fluorescence enhancement and fluorescence quenching, respectively. AMN-SSPy showed advantages such as excellent selectivity to H2S and SO2, strong anti-interference ability, high sensitivity for H2S (LOD 1.03 µM for H2S and 77.08 µM for SO2) and low toxicity. In addition, AMN-SSPy possessed the capacity to successfully image the endogenous and exogenous H2S, and it was also used to demonstrate that Ca2+ could induce accumulation of H2S in cell and zebrafish. Finally, the rapid detection of SO2 by AMN-SSPy in real samples was also established.

Bioimaging and detecting endogenous and exogenous cyanide in foods, living cells and mice based on a turn-on mitochondria-targeted fluorescent probe

A novel fluorescent probe, with advanced features including "turn-on" fluorescence response, high sensitivity, good compatibility, and mitochondria-targeting function, has been synthesized based on structural design for detecting and visualizing cyanide in foods and biological systems. An electron-donating triphenylamine group (TPA) was employed as the fluorescent and an electron-accepting 4-methyl-N-methyl-pyridinium iodide (Py) moiety was used as a mitochondria-targeted localization unit, which formed intramolecular charge transfer (ICT) system. The "turn-on" fluorescence response of the probe (TPA-BTD-Py, TBP) toward cyanide is attributed two reasons, one is the insertion of an electron-deficient benzothiadiazole (BTD) group into the conjugated system between TPA and Py, and the other is the inhibition of ICT induced by the nucleophilic addition of CN^-. Two active sites for reacting with CN^- were involved in TBP molecule and high response sensitivity were observed in tetrahydrofuran solvent containing 3 % H₂O. The response time could be reduced to 150 s, the linear range was 0.25-50 μM, and the limit of detection was 0.046 μM for CN^- analysis. The TBP probe was successfully applied to the detection of cyanide in food samples prepared in aqueous solution, including the sprouting potato, bitter almond, cassava, and apple seeds. Furthermore, TBP exhibited low cytotoxicity, clear mitochondria-localizing capability in HeLa cells and excellent fluorescence imaging of exogenous and endogenous CN^- in living PC12 cells. Moreover, exogenous CN^- with intraperitoneal injection in nude mice could be well monitored visually by the "turn-on" fluorescence. Therefore, the strategy based on structural design provided good prospects for optimizing fluorescent probes.

Development of a responsive probe for colorimetric and fluorescent detection of bisulfite in food and animal serum samples in 100% aqueous solution

Bisulfite (HSO₃^-) has the functions of bleaching, antiseptic, antioxidant, inhibiting bacterial growth, and controlling enzymatic reactions in food. However, long-term consumption of foods containing excessive amounts of bisulfite can be harmful to health. In addition, large doses of sulfur dioxide (SO₂) can cause diarrhea, hypotension, allergic and asthmatic reactions in susceptible individuals. Therefore, it is urgent and essential to explore some rapid, reliable, and convenient tools to detect HSO₃^- in food and SO₂ gas. Herein, we exploited a fluorescent probe, NPO, to detect HSO₃^- in 100 % aqueous solution. The probe has the advantages of easy synthesis, excellent water solubility, significant colorimetric change, good selectivity, high sensitivity, and fast response (within 1 min). Probe NPO was successfully applied for testing strips to visualize the behavior of HSO₃^- and SO₂ gas. Moreover, the probe has been used to monitor the behavior of HSO₃^- in real food samples and animal serum samples.

Reversible colorimetric and NIR fluorescent probe for sensing SO2/H2O2 in living cells and food samples

Preservative sulfur dioxide (SO₂) and bleach hydrogen peroxide (H₂O₂) were widely used in the food industry, at the same time, they were also a redox pair in biological systems. Therefore, the reversible sensing SO₂/H₂O₂ was of great significance in food safety and biology. In this paper, a colorimetric and NIR fluorescent dual channels response probe (DCA-Bba) for SO₂/H₂O₂ based on chromene-barbiturate was developed. DCA-Bba exhibited a rapid and sensitive recognition of SO₂, and the adduct DCA-Bba-HSO₃^- could detect H₂O₂ in PBS (with 10 % DMSO, v/v, pH 7.4) solution. The reversible response of DCA-Bba was implemented by HSO₃^- involved 1,4-addition and H₂O₂ induced elimination reaction. DCA-Bba showed a strong red fluorescence based on the intramolecular charge transfer (ICT) process, after the recognition of SO₂, the fluorescence of the adduct was quenched based on the photoinduced electron transfer (PET) process. And importantly, DCA-Bba had been applied for imaging SO₂/H₂O₂ redox cycles in living cells, as well as could detect the levels of SO₂ in white sugar, biscuit, Chinese liquor and red wine samples.

Simultaneous detection of lysosomal SO2 and viscosity using a hemicyanine-based fluorescent probe

The changes in sulfur dioxide and viscosity of lysosomes are significant indicators in physiological processes and the cell microenvironment. This study aimed to synthesize a hemicyanine-based probe for simultaneous detection of SO₂ and viscosity. The probe could not only rationally detect sulfur dioxide in a semi-aqueous solution with high sensitivity (limit of detection = 0.78 μM) and fast response (within 30 s) but also monitor viscosity via fluorescence emission enhancement at 580 nm. Further, the dual-response probe was successfully used to image SO₂ and viscosity in the lysosomes of living cells.

Small-Molecule Fluorescent Probe for Detection of Sulfite

Sulfite is widely used as an antioxidant additive and preservative in food and beverages. Abnormal levels of sulfite in the body is related to a variety of diseases. There are strict rules for sulfite intake. Therefore, to monitor the sulfite level in physiological and pathological events, there is in urgent need to develop a rapid, accurate, sensitive, and non-invasive approach, which can also be of great significance for the improvement of the corresponding clinical diagnosis. With the development of fluorescent probes, many advantages of fluorescent probes for sulfite detection, such as real time imaging, simple operation, economy, fast response, non-invasive, and so on, have been gradually highlighted. In this review, we enumerated almost all the sulfite fluorescent probes over nearly a decade and summarized their respective characteristics, in order to provide a unified platform for their standardized evaluation. Meanwhile, we tried to systematically review the research progress of sulfite small-molecule fluorescent probes. Logically, we focused on the structures, reaction mechanisms, and applications of sulfite fluorescent probes. We hope that this review will be helpful for the investigators who are interested in sulfite-associated biological procedures.

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.

Novel Colorimetric and NIR Fluorescent Probe for Bisulfite/Sulfite Detection in Food and Water Samples and Living Cells Based on the PET Mechanism

Despite their status of being widely used as food additives, bisulfite (HSO₃^-)/sulfite (SO₃^2-) can pose serious health risks when they are excessively added. Therefore, it is vital to develop a new method for detecting HSO₃^-/SO₃^2- in foodstuff. In this paper, a benzopyran-benzothiazole derivative (probe DCA-Btl) with near-infrared emission was designed and synthesized by constructing a "push-pull" electronic system. DCA-Btl can selectively recognize HSO₃^-/SO₃^2- via a colorimetric and fluorescence dual channel in DMF/PBS (1:1, v/v, pH = 8.4), and the emission wavelength of DCA-Btl can reach 710 nm. The fluorescence quenching of DCA-Btl after recognition of HSO₃^- is attributed to the photoinduced electron transfer (PET) process of the adduct DCA-Btl-HSO₃^- as evaluated by the DFT/TD-DFT method. In addition, DCA-Btl has many advantages, including a large Stokes shift (95 nm), good anti-interference ability, and little cytotoxicity. What's more, DCA-Btl has been successfully applied for the detection of HSO₃^-/SO₃^2- in actual water samples and food samples such as sugar, red wine, and biscuits with satisfying results, as well as for fluorescent imaging of HSO₃^- in living MCF-7 cells.

Research Progress on Multifunctional Fluorescent Probes for Biological Imaging, Food and Environmental Detection

There has been rapid progress in the development of fast, sensitive, cheap and low-cytotoxicity micro-molecule fluorescent probes for application in various fields, including disease diagnosis, food safety and environmental safety. As an analytical tool, dual-function fluorescent probes with dual-emission responses have attracted considerable attention due to their cost-effectiveness and efficiency over single-function sensors. This review primarily describes research progress on multifunctional probes in terms of the reaction type and coordination type, as well as the general design principles of probes. The analytes include reactive oxygen species (ROS), reactive sulfur species (RSS), harmful cations and anions, etc. Multifunctional probes for food, medical and environmental applications are listed for future research. To improve the development of rapid detection methods, trends and strategies in the development of multifunctional fluorescent probes are also discussed.

Rational Construction of a Two-Photon NIR Ratiometric Fluorescent Probe for the Detection of Bisulfite in Live Cells, Tissues, and Foods

In this study, we report a novel ratiometric fluorescent probe with a blue shift of 180 nm based on a D-π-A-A structure. The probe composed of a hydroxyl moiety as a donor, a naphthyl ring as a π bridge, and benzothiazole/hemicyanine as an acceptor has good selectivity and high sensitivity to bisulfite (HSO₃^-) in aqueous solution. Besides one-photon fluorescence properties, the probe possesses excellent two-photon fluorescence properties and is successfully utilized for fluorescence imaging of HSO₃^- in MCF-7 cells and rat liver tissues. More importantly, the probe also has practical application potential for measuring the HSO₃^- content of real food samples.

Mitochondria-Targeted Fluorescent Turn-On Probe for Rapid Detection of Bisulfite/Sulfite in Water and Food Samples

Bisulfite (HSO₃^-)/Sulfite (SO₃^2-) is widely used as a food additive, but excessive use often leads to serious consequences, so the detection of HSO₃^-/SO₃^2- is of great importance. In this paper, a novel 1,4-diethylpiperazine-modified coumarin-benzopyran derivative (probe QLP) has been synthesized and characterized. In PBS (10 mM, pH = 7.4), QLP displays good selectivity and is sensitive for HSO₃^-/SO₃^2- over various analytes with fluorescent "OFF-ON" rapid responding (2 min), long-wavelength emission (600 nm), and a detection limit of 177 nM. With the treatment of HSO₃^-/SO₃^2-, the color of the QLP solution obviously changes from blue-green to yellow, and the fluorescent color of QLP changes from colorless to amaranth. The fluorescence-enhanced mechanism is qualitatively evaluated by density functional theory calculations using the CAM-B3LYP/6-31G (d) method, which reveals that the photoinduced electron transfer leads to the fluorescence emission of the QLP-SO₃H adduct. Importantly, nontoxic QLP can be used to detect HSO₃^-/SO₃^2- in sugar, natural water samples, and living cells and localized to the mitochondria and monitor the mitochondrial HSO₃^-/SO₃^2- level.

A near-infrared emitted fluorescence probe for the detection of biosulfite in live zebrafish, mouse and real food samples

Bisulfite (HSO₃^-) has been widely used as an important food additive in daily life. Furthermore, a normal amount of HSO₃^- plays a significant role in biological systems. However, excessive intake of HSO₃^- will lead to a variety of diseases. Therefore, it is of great significance to develop an efficient fluorescent probe that can be used for detection of HSO₃^- in biological systems and food samples. In this work, a near-infrared (NIR) emitted fluorescent probe (SZY) based on hemicyanine dye was successfully synthesized and applied to detect HSO₃^- in several food samples and live animals. The proposed nucleophilic addition sensing mechanism of SZY towards HSO₃^- has been confirmed by ¹H NMR titration, high resolution mass spectrometry (HR-MS) and density functional theory (DFT) theoretical computation. The HSO₃^--induced nucleophilic reaction with α,β-unsaturated C=C binding of SZY results in the dramatic decline of the UV-vis absorption and remarkable quenching of the fluorescence emission. SZY features the advantages of near infrared emission (centered at 720 nm), high water solubility (in 98% aqueous solution), fast response time (50 s), large Stokes shift (244 nm) and low cytotoxicity. The probe SZY was successfully applied to image of HSO₃^- in live nude mouse and adult zebrafish. Semi-quantitatively analyzing the HSO₃^- level by "naked eye" in several food samples including canned fruit, white wine, white sugar and jasmine tea drinks has been realized by the colorimetric method.

A new near-infrared fluorescence probe synthesized from IR-783 for detection and bioimaging of hydrogen peroxide in vitro and in vivo

A new near-infrared fluorescence probe was developed and synthesized for detection of hydrogen peroxide (H₂O₂) in vitro and in vivo. Synthesized from IR-783, the probe DBIS was designed to connect 4-(Bromomethyl)benzeneboronic acid pinacol ester as the recognizing moiety to the stable hemicyanine skeleton. Reaction of probe DBIS with H₂O₂ would result in the oxidation of phenylboronic acid pinacol ester, and thereby release the near-infrared fluorophore HXIS. The background signal of probe DBIS is very low, which is necessary for sensitive detection. Compared with the existing probes for detecting H₂O₂, the proposed probe DBIS shows excellent optical performance in vitro and in vivo, high selectivity, high sensitivity and good water solubility, as well as near-infrared fluorescence emission 708 nm, with a low detection limit of 0.12 μM. Furthermore, probe DBIS is low cytotoxic, cell membrane permeable, and its applicability has been shown to visualize endogenous H₂O₂ in mice. In addition, it is the first time that paper chips have been used as carrier to detect H₂O₂ through fluorescence signals instead of the traditional liquid phase detection mode of fluorescent probes. These superior characteristics of the probe make it have great application potential in biological systems or in vivo related research.

Double-site-based a smart fluorescent sensor for logical detecting of sulphides and its imaging evaluation of living organisms

Thiophenol and hydrosulphite are a group of toxic environmental pollutants, which contaminate land, water and food exhibiting a serious risk to human health. Herein, we reported a xanthene dye-based sensor (DSF) with dual well-known response sites for visual detecting PhSH and HSO₃^-. Specifically, when DSF reacted with PhSH firstly, the color of the solution changed to blue with bright red fluorescence emission. After added with HSO₃^-, the color of the solution became yellow, and emitted yellow fluorescence signal. However, DSF was first added with HSO₃^-, the color of the solution changed to purple with no-fluorescence emission, and then PhSH was added, the color of the solution changed to yellow with a bright yellow fluorescence. Notably, DSF exhibited high sensitivity and selectivity for PhSH and HSO₃^- detection with a very low detection limits of 2.27 nM and 22.91 nM, respectively. More importantly, DSF could detect PhSH and HSO₃^- in water, real-food and biological systems. Therefore, the experimental results showed DSF as a robust new logical monitoring tool for the detection of PhSH and HSO₃^- in water, real-food samples and biological systems.

Sequential detection of hypochlorous acid and sulfur dioxide derivatives by a red-emitting fluorescent probe and bioimaging applications in vitro and in vivo

A red-emitting fluorescence probe (DP) has been successfully developed for the sequential detection of hypochlorous acid (HOCl) and sulfur dioxide derivatives (SO32−/HSO3−) in vitro and in vivo.

Carbazole-based near-infrared-emitting fluorescence probe for the detection of bisulfite in live animals and real food samples

A carbazole-based near-infrared (NIR)-emitting fluorescent probe (QPM) was successfully developed for the detection of HSO3− in live animals and in real food samples.

A Novel Fluorescence Probe for the Reversible Detection of Bisulfite and Hydrogen Peroxide Pair in Vitro and in Vivo

The detection of changes in the reactive oxygen species (ROS)/reactive sulfur species (RSS) couple is important for studying the cellular redox state. Herein, we developed a 1,8-naphthalimide-based fluorescence probe (NI) for the reversible detection of bisulfite (HSO₃ ^- ) and hydrogen peroxide (H₂ O₂ ) in vitro and in vivo. NI has been designed with a reactive ethylene unit which specifically reacts with HSO₃ ^- by a Michael addition reaction mechanism, resulting in the quenching of yellow fluorescence at 580 nm and the appearing of green fluorescence at 510 nm upon excitation at 500 nm and 430 nm, respectively. The addition product (NI-HSO₃ ) could be specifically oxidized to form the original C=C bond of NI, recovering the fluorescence emission and color. The detection limits of NI for HSO₃ ^- and NI-HSO₃ for H₂ O₂ were calculated to be 2.05 μM and 4.23 μM, respectively. The reversible fluorescence response of NI towards HSO₃ ^- /H₂ O₂ couple can be repeated for at least five times. NI is reliable at a broad pH range (pH 3.0-11.5) and features outstanding selectivity, which enabled its practical applications in biological and food samples. Monitoring the reversible and dynamic inter-conversion between HSO₃ ^- and H₂ O₂ in vitro and in vivo has been verified by fluorescence imaging in live HeLa cells, adult zebrafish and nude mice. Moreover, NI has been successfully applied to detect of HSO₃ ^- levels in food samples.

Colorimetric and Ratiometric Fluorescence Detection of HSO3- With a NIR Fluorescent Dye

Bisulfite (HSO₃^-) has been widely used in food and industry, which has brought convenience to human life, but also seriously endangered human health. In this work, the probe PBI was designed and synthesized to detect bisulfite (HSO₃^-) through nucleophilic addition reaction. The probe PBI showed a selective reaction to HSO₃^- and can quantitatively detect HSO₃^-. At the same time, the color of the probe PBI changed significantly, which provided a simple method for the naked eye to identify HSO₃^-. Finally, it was successfully applied to the fluorescence imaging of HSO₃^- in living cells.

A near-infrared fluorescent probe targeting mitochondria for sulfite detection and its application in food and biology

Sulfur dioxide (SO2) is the main air pollutant in the environment, causing great harm to human health. Abnormal SO2 levels are usually associated with some respiratory diseases, cardiovascular diseases, and neurological disorders (even brain cancer). Therefore, monitoring SO2 levels is helpful to better understand its special physiological and pathological role. Although many fluorescent probes for SO2 have been reported, many of them were not ideal for in vivo imaging due to the short emission wavelength. In this work, a near-infrared fluorescent probe NIR-BN with emission wavelength of 680 nm was constructed by conjugating the benzopyrylium moiety and 6-hydroxy-2-naphthaldehyde. NIR-BN had high selectivity and rapidity for SO2 detection. In addition, the detection limit of NIR-BN was relatively low, which can be used for the determination of sulfite in different sugar samples with high accuracy. Of course, due to the excellent spectral and structural properties of NIR-BN, we have applied NIR-BN to the detection of SO2 in biological systems.

Ultrafast Detection of Sulfur Dioxide Derivatives by a Distinctive "Dual-Positive-Ion" Platform that Features a Doubly Activated but Irreversible Michael Addition Site

Sulfur dioxide (SO₂) is a gaseous signaling molecule and widely used as a preservative for foods, but its excessive intake is closely related to a series of diseases. Therefore, the development of a potent fluorescence probe for the detection of SO₂ in foods and biological systems is of great significance. Herein, we report for the first time a "dual-positive-ion" platform-based fluorescence probe CMQ, designed by a doubly activated but irreversible strategy, which results in its ultrafast response to SO₂ within 5 s in pure aqueous solution together with a low detection limit as 15.6 nM. In addition, the probe was successfully applied for imaging of SO₂ in mitochondria of living cells and zebrafish and prepared as a reagent kit for convenient and instantaneous quantification of HSO₃^- in real food samples.

Rational Development of a New Reaction-Based Ratiometric Fluorescent Probe with a Large Stokes Shift for Selective Detection of Bisulfite in Tap Water, Real Food Samples, Onion Tissues, and Zebrafish

Bisulfite (HSO₃^-) is usually widely added to tap water and food because it has antibacterial, bleaching, and antioxidant effects. However, its abnormal addition would cause a series of serious diseases related to it. Therefore, development of an effective method for HSO₃^- detection was of great significance to human health. In this work, a new reaction-based ratiometric fluorescent probe KQ-SO₂ was rationally designed, which could be used for the highly selective detection of HSO3^- in tap water, real food samples, onion tissues, and zebrafish. Specifically, a positively charged benzo[e]indolium moiety and a carbazole group through a condensation reaction resulted in KQ-SO₂, which displayed two well-resolved emission bands separated by 225 nm, fast response (1 min), and high selectivity and sensitivity toward HSO3^- upon undergoing the Michael addition reaction, as well as low cytotoxicity in vitro. In addition, KQ-SO₂ has been successfully applied for the detection of HSO₃^- in tap water, real food samples, onion tissues, and zebrafish with satisfactory results. We predict that KQ-SO₂ could be used as a powerful tool to reveal the relationship between HSO3^- and the human health.

A ratiometric fluorescent probe for the rapid and specific detection of HSO3 - in water samples

Hydrosulphite (HSO₃ ^- ), as a common and important chemical reagent, is widely used in everyday life, however excessive use and abuse of HSO₃ ^- can cause potential harmful effects on the environment and in biological health. In this paper, we describe the design and preparation of a colorimetric and ratiometric fluorescence probe for the visual detection of HSO₃ ^- (excitation wavelengths were, respectively, 336 nm and 520 nm). This method showed some advantages including simple preparation, high selectivity, fast response, and significant colour and fluorescence ratio (F₄₅₀ /F₅₉₄ ) changes in the presence of HSO₃ ^- . In addition, this probe was used successfully for the detection of HSO₃ ^- in real water samples and showed a good recovery rate range.

A Highly Selective Turn-on Fluorescent and Naked-eye Colourimetric Dual-channel Probe for Cyanide Anions Detection in Water Samples

A highly selective turn-on fluorescent and naked-eye colourimetric dual-channel probe for cyanide anions (CN-) has been designed and characterized. In the mixed solution (DMSO / H₂O, 9:1, v / v), only CN- could cause an increase in the UV absorption intensity and the corresponding fluorescence intensity increased, and other anions had no significant effect on the probe. After treatment with cyanide in the probe solution, the solution showed a noticeable colour change, from light yellow to purple. Moreover, a fluorescence spectrophotometer can be used to observe that the fluorescence intensity of the solution is significantly enhanced. The response of the colourimetric and fluorescent dual-channel probe to CN- was attributed to nucleophilic addition, and the mechanism was determined by ¹H NMR spectroscopy. In addition, this probe was used to detect CN- in actual water samples, including river water, drinking water, and tap water. The spiked CN- recovery rate is very high (97.2%-100.06%), and analytical precision is also very high (RSD < 2%), which shows its feasibility and reliability for detecting cyanide ions in actual water samples.

A reversible near-infrared fluorescence probe for the monitoring of HSO3−/H2O2-regulated cycles in vivo

A near-infrared (NIR) fluorescent probe (XC) was constructed for the reversible detection of HSO3−/H2O2 in biosystems. The practical applications of XC were also demonstrated by the quantitative analysis of HSO3− in white wine and sugar samples.

Resorufin-based responsive probes for fluorescence and colorimetric analysis

The fluorescence imaging technique has attracted increasing attention in the detection of various biological molecules in situ and in real-time owing to its inherent advantages including high selectivity and sensitivity, outstanding spatiotemporal resolution and fast feedback. In the past few decades, a number of fluorescent probes have been developed for bioassays and imaging by exploiting different fluorophores. Among various fluorophores, resorufin exhibits a high fluorescence quantum yield, long excitation/emission wavelength and pronounced ability in both fluorescence and colorimetric analysis. This fluorophore has been widely utilized in the design of responsive probes specific for various bioactive species. In this review, we summarize the advances in the development of resorufin-based fluorescent probes for detecting various analytes, such as cations, anions, reactive (redox-active) sulfur species, small molecules and biological macromolecules. The chemical structures of probes, response mechanisms, detection limits and practical applications are investigated, which is followed by the discussion of recent challenges and future research perspectives. This review article is expected to promote the further development of resorufin-based responsive fluorescent probes and their biological applications.

Reaction-Based Ratiometric and Colorimetric Chemosensor for Bioimaging of Biosulfite in Live Cells, Zebrafish, and Food Samples

In this work, a reaction-based ratiometric and colorimetric sensor was designed and synthesized for probing bisulfite (HSO₃^-) by coupling coumarin (CM) with barbituric (BA) moiety. Further tests have shown that CM-BA has high selectivity and sensitivity for the recognition of HSO₃^-, which can be applied for the detection of HSO₃^- in environmental and biological systems very effectively. The fluorescence intensity ratios (F₄₆₂/F₅₆₈) exhibited an outstanding HSO₃^--dependent response with ultrafast response time (within 20 s) and a lower detection limit (105 nM). Meanwhile, the color of the CM-BA solution changed from green to colorless during the recognition process, and its fluorescence changed from green to blue. The mechanism of response is confirmed by the density functional theory (DFT) model. In summary, CM-BA has demonstrated low toxicity and good permeability, which can be applied for imaging HSO₃^- in cells and zebrafish safely and effectively. Besides, this novel sensor CM-BA successfully realized the quantification of the concentration of HSO₃^- in paper strips and food samples.

Red-Emission Probe for Ratiometric Fluorescent Detection of Bisulfite and Its Application in Live Animals and Food Samples

Key roles of bisulfite (HSO3 -) in food quality assurance and human health necessitate a reliable analytical method for rapid, sensitive, and selective detection of HSO3 -. Herein, a new red-emitting ratiometric fluorescence probe, BIQ, is reported for sensitive and selective detection of HSO3 - in food samples and live animals. Probe BIQ recognizes HSO3 - via a 1,4-nucleophilic addition reaction. As a result of this specific reaction, emission intensities at 625 and 475 nm are dramatically changed, allowing the detection of HSO3 - in a ratiometric fluorescence model in an aqueous solution. The obvious changes of solution color from pink to transparent and fluorescence color from rose-red to cyan allow the detection of HSO3 - by naked eyes. Furthermore, probe BIQ has fast response in color and fluorescence (<2 min), excellent selectivity, and a low detection limit (0.29 μM), which enables its application in HSO3 - detection in food samples and live organisms. The practical applications of probe BIQ are then demonstrated by the visualization of HSO3 - in live animals (zebrafish and nude mouse) as well as the determination of HSO3 - in white wine and sugar.

Imidazo[1,5-α]pyridine-based fluorescent probe with a large Stokes shift for specific recognition of sulfite

By taking advantage of the intramolecular charge transfer (ICT) process, we presented a novel fluorescent probe IPY-SO₂ based on imidazo[1,5-α]pyridine derivative for detecting SO₃^2- with a low detection limit (70 nM). Combining its favorable turn-on fluorescence feature (75-fold), rapid response (5 min), high selectivity, large Stokes shift (174 nm) and low cytotoxicity, IPY-SO₂ was successfully applied to imaging SO₃² in living MCF-7 cells and zebrafish.

A Redox-Switchable Colorimetric Probe for "Naked-Eye" Detection of Hypochlorous Acid and Glutathione

We report the development of a new colorimetric probe (L-ol) for investigations of the redox process regulated by hypochlorous acid (HOCl) and glutathione (GSH). The HOCl/GSH redox-switching cycle process was investigated in detail by UV-vis absorption spectroscopy, colorimetric analysis assay and high-resolution mass spectrometry (HRMS). The switchable absorbance responses were attributed to the HOCl-induced oxidation of the p-methoxyphenol unit to the benzoquinone derivative (L-one) and sequential reduction of L-one to hydroquinone (L-ol') by GSH. In phosphate-buffered saline (PBS) buffer, the absorbance of L-ol at 619 nm underwent a remarkable bathochromic-shift, accompanied by a color change from pale yellow to blue in the presence of HOCl. With further addition of GSH, the absorbance of L-one exclusively recovered to the original level. Meanwhile, the blue-colored solution returned to the naive pale yellow color in the presence of GSH. The detection limits for HOCl and GSH were calculated to be 6.3 and 96 nM according to the IUPAC criteria. Furthermore, L-ol-loaded chromatography plates have been prepared and successfully applied to visualize and quantitatively analyze HOCl in several natural waters.

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.

A chemosensor with a paddle structure based on a BODIPY chromophore for sequential recognition of Cu2+ and HSO3−

In this study, a highly selective chemosensor ML based on a BODIPY fluorescent chromophore was synthesized for sequential recognition of Cu²⁺ and HSO₃⁻ in a CH₃OH/H₂O (99 : 1 v/v) system, which contained three recognition sites and its structure characterized by ¹H NMR, ¹³C NMR and ESI-HR-MS. The sensor ML showed an obvious “on–off” fluorescence quenching response toward Cu²⁺ and the ML-Cu²⁺ complex showed an “off–on” fluorescence enhancement response toward HSO₃⁻. The detection limit of the sensor ML was 0.36 μM to Cu²⁺ and 1.4 μM to HSO₃⁻. In addition, the sensor ML showed a 1 : 3 binding stoichiometry to Cu²⁺ and the recovery rate of ML-Cu²⁺ complex identifying HSO₃⁻ could be over 70%. Sensor ML showed remarkable detection ability in a pH range of 4–8.

A highly selective chemosensor based on a BODIPY chromophore for sequential recognition of Cu²⁺ and HSO₃⁻.

Light-driven visualization of endogenous cysteine, homocysteine, and glutathione using a near-infrared fluorescent probe

Light-driven visualization of endogenous cysteine, homocysteine, and glutathione using a near-infrared fluorescent probe.