Dual-Responsive Benzo-Hemicyanine-Based Fluorescent Probe for Detection of Cyanide and Hydrogen Sulfide: Real-Time Application in Identification of Food Spoilage

Bodipy-Based highly sensitive hydrogen sulfide fluorescent probe and its fluorescence imaging in cells and zebrafish

Hydrogen sulfide (H2S) is a crucial endogenous gasotransmitter that plays a role in various physiological and pathological processes. Therefore, accurate and rapid monitoring of H2S in organisms is highly significant for understanding the underlying pathological mechanisms and facilitating early diagnosis of related diseases. In this study, we developed a novel fluorescent probe, B-CHO-NO2, based on a bodipy fluorophore, which exhibits excellent sensitivity and selectivity towards H2S. The design of the probe exploits the nucleophilicity of H2S by introducing a formyl group as the ortho-participating moiety, significantly enhancing the reaction rate with H2S. In cellular and zebrafish models, the probe B-CHO-NO2 successfully achieved fluorescence imaging of endogenous and exogenous H2S. The development of probe B-CHO-NO2 provides a powerful tool for biological studies of H2S and diagnosis of related diseases.

Rapidly responsive and highly selective NIR fluorescent probe for detecting hydrogen sulfide in food samples and living cells

Hydrogen sulfide (H2S) is a pungent gas that is one of the key mediators of signal transduction in biological systems, and its presence is related to the freshness of some protein foods. Using phenothiazine derivatives as fluorophores and 2, 4-dinitrobenzene sulfonate (DNBS) fragments as reaction groups, a near-infrared (NIR) probe WX-HS for H2S identification was designed. With the addition of H2S, WX-HS appeared a strong fluorescence signal at 660 nm with short reaction time (90 s) and high sensitivity, and fluorescence state change from non-fluorescent to orange-red. In addition, WX-HS could effectively detect H2S produced during food oxidation. Based on its low cytotoxicity, the WX-HS probe further enabled the detection and imaging of H2S in A549 cells.

The Application of Hydrogen Sulfide Fluorescent Probe in Food Preservation, Detection and Evaluation

This work primarily reviewed the response mechanism of fluorescent probes for H2S detection in foodstuffs in recent years, as well as the methodologies employed for detecting foodstuffs. Firstly, the significance of studying H2S gas as an important signaling molecule is introduced. Subsequently, a review of the response mechanism of the scientific community on how to detect H2S in foodstuffs samples by fluorescent probe technology is carried out. Secondly, the methods commonly used for detecting foodstuffs samples are discussed, including the test strip method and the spiking recovery methods. Nevertheless, despite the significant advancements in this field, there remain some research gaps. Finally, the article identifies the remaining issues that require further attention in current research and proposes avenues for future investigation. More importantly, this work identifies the current limitations of research in this field and proposes future applications of fluorescent probes for H2S in assessing food freshness and determining food spoilage. Therefore, this review will provide robust technical support for the protection of consumer health and the advancement of the sustainable development of the food industry and also put forward some new ideas and suggestions for future research.

Near-infrared fluorescent probe for detection of hydrogen sulfide in water samples and food spoilage

Hydrogen sulfide (H2S) is a common toxic gas that threatens the quality and safety of environmental water and food. Herein, a new near-infrared fluorescent probe DTCM was synthesized and characterized by single crystal X-ray diffraction for sensing H2S. It exhibited a remarkable "turn-on" near-infrared (NIR) emission response at 665 nm with a remarkably massive Stokes shift of 175 nm, super-rapid detection ability (within 30 s), excellent photostability, high selectivity and sensitivity (limit of detection, LOD = 58 nM). Additionally, the probe was successfully utilized for the detection of H2S in environmental water samples. The DTCM-loaded test papers enabled convenient and real-time monitoring of H2S produced by food spoilage.

Multicolor emissive carbon dot-based fluorometric analysis platform for rapid quantification and discrimination of nitroimidazole antibiotic residues

The development of efficient, rapid, portable, and accurate analysis of veterinary drug residues in food matrices is in great demand for food safety assessment. Here, we have developed a smartphone-integrated platform for fluorometric quantification of metronidazole (MNZ) residues and constructed a sensor array for discrimination of different nitroimidazole antibiotics (NIIMs). Multicolor CDs (B-CDs, C-CDs, Y-CDs, and R-CD) were prepared and showed different fluorescence response to MNZ. The fluorescence of C-CDs was quenched Because of the inner filter effect (IFE) between the C-CDs and MNZ, while that of R-CDs was enhanced due to the passivation of surface defects by MNZ. Based on the response pattern, the fluorometric quantification of MNZ based on the fluorescence images of C-CD + R-CD system (R/G values) was achieved with a low detection limit of 0.45 μM. By designing a smartphone-integrated platform, the analysis can be completed within 20 min. In addition, a fluorescence sensor array based C-CDs and R-CDs was also developed. The unique fingerprint of each NIIMs was obtained by linear discriminant analysis (LDA) of the response patterns, indicating an effective discrimination of five NIIMs. Moreover, the platform was used for quantification of MNZ in food samples and the recoveries were within 84.0-106.3 % with relative standard deviations 1.2-10.2 %. Therefore, the proposed method shows great potential as a universal platform for rapid detection of veterinary drug residues.

Activity-Based Fluorescent Probes for Hydrogen Sulfide and Related Reactive Sulfur Species

Hydrogen sulfide (H2S) is not only a well-established toxic gas but also an important small molecule bioregulator in all kingdoms of life. In contemporary biology, H2S is often classified as a "gasotransmitter," meaning that it is an endogenously produced membrane permeable gas that carries out essential cellular processes. Fluorescent probes for H2S and related reactive sulfur species (RSS) detection provide an important cornerstone for investigating the multifaceted roles of these important small molecules in complex biological systems. A now common approach to develop such tools is to develop "activity-based probes" that couple a specific H2S-mediated chemical reaction to a fluorescent output. This Review covers the different types of such probes and also highlights the chemical mechanisms by which each probe type is activated by specific RSS. Common examples include reduction of oxidized nitrogen motifs, disulfide exchange, electrophilic reactions, metal precipitation, and metal coordination. In addition, we also outline complementary activity-based probes for imaging reductant-labile and sulfane sulfur species, including persulfides and polysulfides. For probes highlighted in this Review, we focus on small molecule systems with demonstrated compatibility in cellular systems or related applications. Building from breadth of reported activity-based strategies and application, we also highlight key unmet challenges and future opportunities for advancing activity-based probes for H2S and related RSS.

Aggregation-induced emission activity of sensor TBM-C1 hybrid of methoxy-triphenylamine (OMe-TPA) and dicyanovinyl for cyanide detection in aqueous THF: Mechanistic insights and potential applications

A series fluorescent probes (TBM-Cx (x = 1, 4, 8)) were designed based on embedding various alkoxy chains on the electron donor of triphenylamine (TPA)-based dicyanovinyl (MT) compound with an electron-deficient benzothiadiazole (BTD) for sensitive, selective, and visualizing detection of cyanide in aqueous solution. Due to the nucleophilic addition of CN-, the intramolecular charge transfer (ICT) of these probes was inhibited by the destroyed conjugated structure, exhibiting excellent "turn-on" fluorescence response toward cyanide anion (CN-) in tetrahydrofuran (THF). However, the alkoxy chains with different lengths embedded in TPA not only enhance the sensitivity and solubility, but also regulate the emission behavior from ICT to aggregation-induced emission (AIE) characteristics. The binding mechanism and AIE sensing performances between the probes and CN- have been investigated and compared in THF/water mixture by spectral tools and theoretical calculations. The results showed that the ICT-based TBM-C1 probe with methoxy chain showed significantly turn-on fluorescence response to CN- as low as 0.077 μM in THF/water solution at high water fraction (90 %). Due to the AIE sensing process, TBM-C1 was successfully employed to determine CN- in food and water samples, image CN- in living cells and BALB/c mice, and prepare test kits for visualizing cyanide.

An innovative fluorescent probe for the detection of cyanide - enhanced sensitivity by controlling its electrostatic potential and suitable for applications such as cell imaging and food analysis

As cyanide is a huge hazard to the environment and human health, the study of the method of detecting low concentrations of cyanide is of great significance. In general, materials with strong positive electrostatic properties can use electrostatic attraction to enrich anions in the water near the materials, then realize rapid detection of low concentration anions by fluorescent probes. In this paper, fluorescent probes PI-S, PI-I and PI-N with cyanide-specific recognition and different charges were synthesized to study the relationship between the charge effect of probes and the sensing sensitivity. Through the zeta potential test and the calculation of the surface electrostatic potential, the positive electricity of PI-S, PI-I and PI-N gradually increased, the ΔG < 0 of the adsorption process gradually decreased, CN- could be aggregated to the vicinity of probes. As a result, the detection limit of the probe was gradually reduced from 1.07 × 10-6 to 5.03 × 10-8 M, the sensitivity was significantly enhanced. Therefore, this is expected to be a new strategy to improve the sensitivity of anion probes by increasing the positive electricity of molecules. In addition, PI-N has good anti-interference ability, short response time and certain application value in cell imaging and identification of endogenous cyanide in food.

Development of europium(III) complex fluorescent probe for hydrogen sulfide detection and its application in water samples

Hydrogen sulfide (H2 S) is a crucial endogenous signaling component in organisms that is involved in redox homeostasis and numerous biological processes. Modern medical research has confirmed that hydrogen sulfide plays an important role in the pathogenesis of many diseases. Herein, a fluorescent probe Eu(ttbd)3 abt based on europium(III) complex was designed and synthesized for the detection of H2 S. Eu(ttbd)3 abt exhibited significant quenching for H2 S at long emission wavelength (625 nm), with rapid detection ability (less than 2 min), high sensitivity [limit of detection (LOD) = 0.41 μM], and massive Stokes shift (300 nm). Additionally, this probe showed superior selectivity for H2 S despite the presence of other possible interference species such as biothiols. Furthermore, the probe Eu(ttbd)3 abt was successfully applied to detect H2 S in water samples.

Development of a Water-Soluble Fluorescent Probe Based on Natural Flavylium for Mercury(II) Ion Detection and Clinical Antidote Evaluation

The health hazard posed by Hg2+ makes it imperative to develop a fast and convenient means for detecting Hg2+ in water samples and living objects. While fluorescence sensing technology is considered a promising candidate, the poor water solubility and fluorescence quenching in aqueous solutions of most existing probes limit their practical application. To overcome this, we developed a natural flavylium-inspired fluorescent probe with excellent water solubility. Our probe demonstrated outstanding performance of high sensitivity (LOD = 0.47 nM), fast response (<10 min), and great selectivity for Hg2+. Notably, we validated its applicability in real water, urine samples, and living cells. Furthermore, the probe was successfully applied to evaluate the effectiveness of antidotes for clinical Hg2+ poisoning.