HS- facilitated sulfur pyran realizing hydrogen sulfide detection and imaging in HepG2 cells and chlorella

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.

Fluorescence Probes for Reactive Sulfur Species in Agricultural Chemistry

Sulfur is an element that is indispensable throughout the growth of plants. In plant cells, reactive sulfur species (RSS) play a vital role in maintaining cellular redox homeostasis and signal transduction. There is demand accordingly for a simple, highly selective, and sensitive method of RSS detection and imaging for monitoring dynamic changes and clarifying the biological functions of RSS in plant systems. Fluorescent analysis based on organic small-molecule fluorescent probes is an effective and specific approach to tracking plant RSS characteristics. This perspective summarizes the recent progress regarding organic small-molecule fluorescent probes for RSS monitoring, including small-molecule biological thiols, hydrogen sulfide, and sulfane sulfurs, in plants; it also discusses their response mechanism toward RSS and their imaging applications in plants across the agricultural chemistry field.

Emerging analytical tools for the detection of the third gasotransmitter H2S, a comprehensive review

BACKGROUND

Hydrogen sulfide (H2S) is currently considered among the endogenously produced gaseous molecules that exert various signaling effects in mammalian species. It is the third physiological gasotransmitter discovered so far after NO and CO. H2S was originally ranked among the toxic gases at elevated levels to humans. Currently, it is well-known that, in the cardiovascular system, H2S exerts several cardioprotective effects including vasodilation, antioxidant regulation, inhibition of inflammation, and activation of anti-apoptosis. With an increasing interest in monitoring H2S, the development of analysis methods should now follow.

AIM OF REVIEW

This review stages special emphasis on the several analytical technologies used for its determination including spectroscopic, chromatographic, and electrochemical methods. Advantages and limitations with regards to the application of each technique are highlighted with special emphasis on its employment for H2S in vivo measurement i.e., biofluids, tissues.

KEY SCIENTIFIC CONCEPTS AND IMPORTANT FINDINGS OF REVIEW

Fluorescence methods applied for H2S measurement offer an attractive non-invasive and promising approach in addition to its selectivity, however they cannot be considered as H2S-specific probes. On the other hand, colorimetric assays are among the most common methods used for in vitro H2S detection, albeit their employment in vivo H2S measurement has not yet been possible . Separation techniques such as gas or liquid chromatography offer higher selectivity compared to direct spectrophotometric or fluorescence methods especially for suitable for endpoint H2S measurements i.e. plasma or tissue samples. Despite all the developed analytical procedures used for H2S determination, the need for highly selective, much work should be devoted to resolve all the pitfalls of the current methods.

Hydrogen sulfide sensing using an aurone-based fluorescent probe

Hydrogen sulfide detection and sensing is an area of interest from both an environmental and a biological perspective. While many methods are currently available, the most sensitive and biologically applicable ones are fluorescence based. In general, these fluorescent probes are based upon large, high-molecular weight, well-characterized fluorescent scaffolds that are synthetically demanding to prepare and difficult to tune and modify. In this study, we have reported a new reduction-based, rationally designed and synthesized turn-on fluorescent probe (Z)-2-(4′-azidobenzylidene)-5-fluorobenzofuran-3(2H)-one (6g) utilizing a low molecular weight aurone fluorophore. During these studies, the modular nature of the synthesis was used to quickly overcome problems with solubility, overlap of excitation of the probe and reduced product, and rate of reaction, resulting in a final compound that is efficient and sensitive for the detection of hydrogen sulfide. The limitation of slow reaction and the reduced fluorescence in a biologically relevent medium was solved by employing cationic surfactant cetyltrimethyl ammonium bromide (CTAB). The probe features a high fluorescence enhancement, fast response (10–30 min), and good sensitivity (1 μm) and selectivity for hydrogen sulfide.

Hydrogen sulfide detection and sensing is an area of interest from both an environmental and a biological perspective.

Functionalized Copper Nanoclusters-Based Fluorescent Probe with Aggregation-Induced Emission Property for Selective Detection of Sulfide Ions in Food Additives

In this paper, a novel and facile synthetic method of 3-mercaptopropionic acid functionalized copper nanoclusters with aggregation-induced emission (AIE) induced by Cu²⁺ (Cu²⁺@MPA-Cu NCs) was developed by a one-pot reaction as a fluorescent probe for the detection of sulfide ion (S^2-). The prepared Cu²⁺@MPA-Cu NCs behaved as aggregated clusters and had strong pink fluorescence under 365 nm UV light with excellent fluorescence emission at 610 nm. The quantum yield increased from 0.56% to 4.8% before and after Cu²⁺ added. The presence of S^2- would strongly bind to Cu²⁺, which caused the structure of the aggregated Cu²⁺@MPA-Cu NCs to be destroyed and then the fluorescence quenched. On the basis of this principle, a fluorescent probe was constructed for the detection of S^2- with a very good linearity in the range 0-600 μM (R² = 0.9843) and a detection limit of 26.3 nM. Finally, the nanohybrids were successfully demonstrated for the application in the selective detection of S^2- in food additives. This study essentially paved a new avenue for effectively developing an easy sensor platform for S^2- measurements in food additives.

Current approaches for detection of hydrogen sulfide and persulfidation in biological systems

The past decades have witnessed hydrogen sulfide (H₂S) serving as gaseous signaling molecule participating in diverse cellular and physiological processes in biological systems. Recently, a considerable number of studies highlight the signaling role of this redox-regulating molecule occurs via persulfidation, which is a post-translation modification of protein cysteine residues by covalent addition of thiol group form persulfide. However, our current understanding on detection of H₂S and persulfidation in biological systems still lags behind. This review aims to summarize current approaches for measuring H₂S and persulfidated levels in biological systems. Meanwhile, potential interference may exist in plant research has been proposed and discussed.

Point-of-care testing and optimization of sample treatment for fluorometric determination of hydrogen sulphide in plasma of cardiovascular patients

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A comparative sample preparation methodology for fluorometric determination of H₂S in plasma.

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Sample treatment protocol is critical to reliable results for determination of gasotransmitter.

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Portable H₂S Analyser was designed, manufactured and verified as POCT for the gas in the ambulance.

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Validation in human plasma proved efficiency of H₂S Analyser in determining H₂S in MI patients.

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H₂S is elevated in MI patients compared to normal controls up to 10 h from emergence of symptoms.

Introduction: Hydrogen sulphide (H₂S) is one of the gasotransmitters that was reported to have a cardioprotective effect at its physiological levels in blood. Previous determinations of H₂S levels in cardiovascular disease (CVD) patients suffered from diversity of analytical methods, different targeted chemical forms of the gas, and multitude of matrices assessed.

Objectives: In this study, a comparative biological sample preparation study is detailed for optimum selective determination of the unionized form of H₂S in blood of CVD patients using a new in-house POCT portable spectrofluorometer together with a Reagent-Analyser system.

Methods: Dansyl azide was synthesized to react with hydrogen sulfide in biological matrix to produce the fluorescent dansyl amide. Fluorescence was measured at λ_ex 340 nm and λ_em 517 nm in the new in-house POCT portable spectrofluorometer. The method was validated according to ICH guidelines. Several blood sample treatments and reaction protocols were compared to achieve maximum fluorescence yield.

Results: The H₂S Analyser was verified in comparison to a benchtop spectrofluorometer where linearity was confirmed in the range of 3–300 μM, LOD being 1 μM, at λ_ex 340 nm and λ_em 517 nm. Sample treatment involving blood centrifugation followed by addition of reagent on plasma produced maximum fluorescence yield. Analysis of blood samples of myocardial infarction (MI) patients and controls showed elevated levels of H₂S in MI patients (28 μM ± 1.111) vs. controls (23 μM ± 1.036) at p = 0.0015.

Conclusion: The study is novel in being a POCT approach for selective determination of H₂S molecular form in plasma after simple optimized sample treatment. The study confirms that MI is associated with H₂S elevated levels up to 10 hours from emergence of symptoms.