Ratiometric sensing of sulfite/bisulfite ions and its applications in food samples and living cells

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.

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 Simple Selective Probe for Lysine Detection in Tablets, Food Samples and Cells

A novel probe ITQ (9-(((E)-1 H-inden-1-ylidene)methyl)-8-(3-(((E)-1 H-inden-1-ylidene)methyl)phenoxy)-2,3,6,7-tetrahydro-1 H,5 H-pyrido[3,2,1ij]quinolone) was successfully designed and synthesized to detect amino acid lysine (Lys). The selective sensing behavior of the probe ITQ was observed using absorption and emission spectral results. Further, the probe ITQ exhibits a strong binding affinity for Lys [1.4 × 104 M- 1] and detects and quantifies Lys even in its nanomolar concentration. Moreover, the probe ITQ detects Lys at 1:2 binding stoichiometry with suitable biological pH [4-11]. Furthermore, the probe ITQ was also successfully utilized to detect Lys in tablets, real samples (avocado, soyabean and pork) and in live HeLa cells.

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.

Dual-response and lysosome-targeted fluorescent probe for viscosity and sulfur dioxide derivatives

Viscosity and sulfur dioxide levels are important factors to evaluate the changes of cell micro-environment because a series of diseases usually occur when they are abnormal. At present, dual-response probes that can detect both viscosity and sulfur dioxide are rare. Therefore, we developed a novel fluorescent probe CBN for simultaneous detection of sulfur dioxide and viscosity. Besides, probe CBN could target lysosome of which normal function will be disrupted by the abnormality of viscosity. Therefore, probe CBN has the potential to be served as an effective biological tool to monitor the intracellular micro-environment.

A bis-chalcone based colorimetric probe for the selective detection of bisulfite/sulfite anions: exploring surfactant promoted Michael addition of anions to α, β-unsaturated ketones

A probe, (1E,4E)-1,5-di(thiophen-2-yl)penta-1,4-dien-3-one, was developed for rapid, colorimetric, and selective detection of bisulfite/sulfite anions in aqueous solutions. This probe is based on the Michael addition reaction which is favoured in the presence of cationic micellar medium CTAB. CTAB promoted Michael addition is an effective tool to determine SO₂ toxicity, which is mainly expressed in terms of collective concentration of bisulfite and sulfite anions. The probe showed high selectivity and sensitivity toward bisulfite and sulfite over other interfering anions, with a detection limit of 0.43 μM and 0.23 μM, respectively. The possible recognition mechanism of the probe and the analyte was illustrated by NMR, HR-MS, IR, and computational analysis. Moreover, this probe showed great potential for the detection of bisulfite/sulfite in real samples, such as crystal sugar and brown sugar.

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.

Starch-Based Carbon Dots for Nitrite and Sulfite Detection

Nitrite and sulfite play important roles in human health and environmental science, so it is desired to develop a facile and efficient method to evaluate NO2 - and SO3 2- concentrations. In this article, the use of green alternatives with the potential of multi-functionality has been synthesized to detect nitrite and sulfite based on fluorescent probe. The carbon dots (CDs) with starch as only raw materials show fluorescence turn "on-off-on" response towards NO2 - and SO3 2- with the limits of detection of 0.425 and 0.243 μМ, respectively. Once nitrite was present in the solution, the fluorescence of CDs was quenched rapidly due to the charge transfer. When sulfite was introduced, the quenching fluorescence of CDs was effectively recovered because of the redox reaction between NO2 - and SO3 2-, and thus providing a new way for NO2 - and SO3 2- detection. Owing to their excellent analytical characteristics and low cytotoxicity, the "on-off-on" sensor was successfully employed for intracellular bioimaging of NO2 - and SO3 2-.