Fluorescence chemosensors for hydrogen sulfide detection in biological systems

A mitochondria-targeted chemiluminescent probe for detection of hydrogen sulfide in cancer cells, human serum and in vivo

Hydrogen sulfide (H2S) as a critical messenger molecule plays vital roles in regular cell function. However, abnormal levels of H2S, especially mitochondrial H2S, are directly correlated with the formation of pathological states including neurodegenerative diseases, cardiovascular disorders, and cancer. Thus, monitoring fluxes of mitochondrial H2S concentrations both in vitro and in vivo with high selectivity and sensitivity is crucial. In this direction, herein we developed the first ever example of a mitochondria-targeted and H2S-responsive new generation 1,2-dioxetane-based chemiluminescent probe (MCH). Chemiluminescent probes offer unique advantages compared to conventional fluorophores as they do not require external light irradiation to emit light. MCH exhibited a dramatic turn-on response in its luminescence signal upon reacting with H2S with high selectivity. It was used to detect H2S activity in different biological systems ranging from cancerous cells to human serum and tumor-bearing mice. We anticipate that MCH will pave the way for development of new organelle-targeted chemiluminescence agents towards imaging of different analytes in various biological models.

Ratiometric fluorescence assay for sulfide ions with fluorescent MOF-based nanozyme

A novel ratiometric fluorescence strategy for sulfide ions (S^2-) analysis has been developed using metal-organic framework (MOF)-based nanozyme. NH₂-Cu-MOF displays blue fluorescence (λem = 435 nm) originating from 2-amino-1,4-benzenedicarboxylic acid ligand. Besides, it possesses oxidase-like activity due to Cu²⁺ node, which can trigger chromogenic reaction. o-Phenylenediamine (OPD), as a common enzyme substrate, can be oxidized by NH₂-Cu-MOF to form luminescent products (oxOPD) (λem = 570 nm). Inner filter effect occurs between oxOPD and MOF. Upon exposure to S^2-, oxidase-like activity of MOF is depressed significantly because of the generation of CuS. On one hand, the amount of free Cu²⁺ decreases, affecting the yielding of oxOPD. On the other hand, CuNPs with larger size are obtained during the oxidation-reduction reaction between Cu²⁺ and OPD, which show weaker autocatalytic ability for OPD oxidation. These result in the decrease and increase of intensities at 570 and 435 nm, respectively. This method exhibits sensitive and selective responses towards S^2- with LOD of 0.1 μM. Furthermore, such ratiometric strategy has been applied to detect S^2- in food samples.

Fluorescence 'Turn-on' Dual Sensor for Selective Detection of Cd2+ and H2AsO4- in Water

A multi responsive fluorescent probe, N',2-bis(E-4-(diethylamino)-2-hydroxybenzylidene)hydrazine-1-carbothiohydrazideV(H₂L) has been synthesized through one step condensation method. Probe, H₂L shows 'turn-on' dual sensing properties towards Cd²⁺ and H₂AsO₄^- at two distinct wavelength. The probe (H₂L) is spectroscopically characterized and the chemo-sensing mechanism has been demonstrated through ¹H NMR, absorption, steady state and time resolved emission study. The most promising advantage of the probe is its application in the one-pot detection of Cd²⁺ (λ_em = 462 nm) and H₂AsO₄^-(λ_em = 492 nm) where intense emission appears at two different wavelengths and the observed limit of detection (LOD) of H₂L towards Cd²⁺ and H₂AsO₄^- are 2.67 × 10^-8 M and 5.14 × 10^-6 M respectively. Further the 'turn-on' emission property of H₂L towards Cd²⁺ is applied to construct INHIBIT logic gate.

An ESIPT-based reversible ratiometric fluorescent sensor for detecting HClO/H2S redox cycle in living cells

HClO and H₂S, as two kinds of crucial small biomolecules, are endowed various roles in biological organisms. The redox balance between HClO and H₂S is closely related to the physiological and pathological processes. Thus, it is significant to monitor the redox process between HClO and H₂S. Inspired by the advantages of ratiometric fluorescent probes, we firstly developed a reversible ratiometric fluorescent probe (BT-Se) for HClO and H₂S via combination of phenyl selenide as the response group and 2-(2'-hydroxyphenyl)benzothiazole dye as the fluorophore. The proposed probe BT-Se could detect HClO with well-separated dual emission (110 nm), fast response, good selectivity and sensitivity owing to the oxidation reaction of the Se atom induced by HClO. Moreover, only H₂S could effectively recover the fluorescence of the detection system to the original state via H₂S induced-reduction of selenoxide. Cell imaging studies demonstrated that the probe BT-Se was capable of ratiometric monitoring the changes of intracellular HClO/H₂S, which suggested that it has great potential for researching the biological functions of HClO and H₂S.

Sensing mechanism of a new fluorescent probe for hydrogen sulfide: photoinduced electron transfer and invalidity of excited-state intramolecular proton transfer

It is of great significance for biological research to develop efficient detection methods of hydrogen sulfide (H2S). When DFAN reacts with H2S, 2,4-dinitrophenyl ether group acting as an electron acceptor generates a hydroxyl-substituted 2,4-dinitrophenyl ether group, resulting in the disappearance of photoinduced electron transfer (PET), and the new formed DFAH can be observed, while being accompanied by a significant fluorescence. In the present study, the PET sensing mechanism of probe DFAN and the excited state intramolecular proton transfer (ESIPT) process of DFAH have been explored in detail based on the density functional theory (DFT) and time-dependent density functional theory (TD-DFT) methods. Our theoretical results show that the fluorescence quenching of DFAN is caused by the PET mechanism, and the result of ESIPT mechanism is not due to the large Stokes shift fluorescence emission of DFAH. We also optimized the geometric structure of the transition state of DFAH. The frontier molecular orbitals and potential barrier show that the ESIPT process does not easy occur easily for DFAH. The enol structure of DFAH is more stable than that of the keto structure. The absence of the PET process resulted in the enol structure emitting strong fluorescence, which is consistent with the single fluorescence in the experiment. Above all, our calculations are sufficient to verify the sensing mechanism of H2S using DFAN.

Visual detection of S2- with a paper-based fluorescence sensor coated with CdTe quantum dots via headspace sampling

A simple method was developed in this work for facile and visual detection of S^2- using a paper-based fluorescence (FL) sensor coated with CdTe quantum dots (QDs) by headspace sampling. With the addition of hydrochloric acid, the target S^2- in the liquid phase would transform to H₂ S, which was released to headspace and quenched the FL of CdTe QDs in a linear manner through a gas-solid reaction, with any possible liquid-phase interference avoided. The regular quenching caused by S^2- in analyte solution with increased concentration could be easily observed by the naked eye, and the limit of detection (LOD) for this method was 0.13 μM and 0.93 μM for FL and visual sensing, respectively, comparable or not to that by other sensing probes. A relative standard deviation of 1.2% was accomplished from seven replicated measurements, implying the high reproducibility, and the recovery for the spiked water samples ranging from 94 to 103%, and illustrating the satisfactory reliability of this method. Moreover, the preparation of this paper sensor was facile and did not require any complicated or time-consuming procedures for additional modification or functionalization as for other probes previously reported.

A paper-based colorimetric chemosensor for rapid and highly sensitive detection of sulfide for environmental monitoring

In this study, we report on paper-based colorimetric detection of sulfide using a newly synthesized chemical acting as a chemosensor, based on the deprotonation mechanism. Paper strips were also fabricated and incorporated with the chemosensor for on-site monitoring. The presence of sulfide induced deprotonation of a hydroxyl group of the chemosensor, which eventually resulted in a distinct spectral change in the tube as well as a visible color change on a paper strip. The chemosensor showed a highly selective colorimetric response to sulfide by changing its color from colorless to yellow without any interference from a mixture containing other anions. Moreover, the chemosensor effectively differentiated sulfide from other thiols, including cysteine and glutathione. The chemosensor colorimetrically detected sulfide with a fast response time of 10 s under physiological conditions. Practically, the paper test strip enabled colorimetric visualization of as low as 30 μM sulfide and a good recovery in quantitative analysis in water samples. The introduced paper-based chemosensor is a promising colorimetric strategy with rapid, selective, and sensitive sensing abilities for sulfide monitoring in environmental water samples.

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.

Fluorescent salen-type Zn(II) Complexes As Probes for Detecting Hydrogen Sulfide and Its Anion: Bioimaging Applications

In this work, we investigate the mode of interaction of a family of fluorescent zinc complexes with HS- and H2S. Different experiments, performed by diverse spectroscopic techniques, provide evidence that HS- binds the zinc center of all the complexes under investigation. Treatment with neutral H2S exhibits a markedly different reactivity which indicates selectivity for HS- over H2S of the systems under investigation. Striking color changes, visible to the naked eye, occur when treating the systems with HS- or by an H2S flow. Accordingly, also the fluorescence is modulated by the presence of HS-, with the possible formation of multiple adducts. The results highlight the potential of the devised systems to be implemented as HS-/H2S colorimetric and fluorescent sensors. Bioimaging experiments indicate the potential of using this class of compounds as probes for the detection of H2S in living cells.

A natural cyanobacterial protein C-phycoerythrin as an HS- selective optical probe in aqueous systems

A naturally fluorescent cyanobacterial protein C-phycoerythrin (CPE) was investigated as a fluorescent probe for biologically and environmentally important hydrosulphide (HS^-) ion. It was selective for HS amongst a large anion screen and the optical response was rapid. Sequential UV-visible titration showed considerable peak shift and attenuation with increasing [HS^-] while fluorescence titration proved that HS^- quenched CPE fluorescence in a concentration dependent manner. The linear response range was 0-2 mM HS^- while the Stern Volmer curve was non-linear and the limit of detection was 185.12 μM. Except bicarbonate and glycine, no anion or biomolecule interfered with the detection even at 10 times the concentration of HS^-. It was also free of influences from other sulphur forms like sulphite, sulphate and thiosulphate. CPE reliably detected HS^- in freshwater and effluent samples, though some under- and over - estimation was evident. The % recovery ranged from ~96 to 105% (RSD ~ 0.035-0.188%). FTIR analysis showed significant changes in the amide I and II regions of CPE, along with minor modifications in the amide III region as well, showing that HS^- was able to influence the protein secondary structure at higher concentrations.

Small-molecule fluorescent probes for imaging gaseous signaling molecules: current progress and future implications

Endogenous gaseous signaling molecules including nitric oxide (NO), carbon monoxide (CO) and hydrogen sulfide (H2S) have been demonstrated to perform significant physiological and pharmacological functions and are associated with various diseases in biological systems. In order to obtain a deeper insight into their roles and mechanisms of action, it is desirable to develop novel techniques for effectively detecting gaseous signaling molecules. Small-molecule fluorescent probes have been proven to be a powerful approach for the detection and imaging of biological messengers by virtue of their non-invasiveness, high selectivity, and real-time in situ detection capability. Based on the intrinsic properties of gaseous signaling molecules, numerous fluorescent probes have been constructed to satisfy various demands. In this perspective, we summarize the recent advances in the field of fluorescent probes for the detection of NO, CO and H2S and illustrate the design strategies and application examples of these probes. Moreover, we also emphasize the challenges and development directions of gasotransmitter-responsive fluorescent probes, hoping to provide a general implication for future research.

Design, synthesis and evaluation of a novel fluorescent probe to accurately detect H2S in hepatocytes and natural waters

Design and synthesis of fluorescent probe with fast response, excellent water solubility and good hepatocyte-targeting capacity to detect hydrogen sulfide (H₂S) in hepatocytes and water samples is of great significance. Here, a novel fluorescent probe QL-Gal-N₃ for detection of H₂S was designed and synthesized based on H₂S-mediated azide reduction strategy. This sensor demonstrated low toxicity, fast response (within 1 min), high selectivity and low detection limit (as low as 126 nM in water) for the detection of H₂S. HeLa, A549 and HepG-2 cells were chosen to investigate the hepatocyte-targeting ability of QL-Gal-N₃ respectively. The results indicated that the specific recognition of ASGPR over-expressed in hepatocytes by galactose group was an important reason for the good targeting ability of probe QL-Gal-N₃. Furthermore, due to the introduction of glycosyl moiety, the water solubility of fluorescent probe was enhanced obviously. It was successfully applied for the detection of H₂S in environmental water samples including river water, tap water, lake water and waste water.

A covalent organic polymer as an efficient chemosensor for highly selective H2S detection through proton conduction

An interdigitated electrode fabricated with a covalent organic polymer (COP) acts as an efficient H₂S gas sensor at room temperature.

Smart H2S-Triggered/Therapeutic System (SHTS)-Based Nanomedicine

Hydrogen sulfide (H2S) is of vital importance in several biological and physical processes. The significance of H2S-specific detection and monitoring is emphasized by its elevated levels in various diseases such as cancer. Nanotechnology enhances the performance of chemical sensing nanoprobes due to the enhanced efficiency and sensitivity. Recently, extensive research efforts have been dedicated to developing novel smart H2S-triggered/therapeutic system (SHTS) nanoplatforms for H2S-activated sensing, imaging, and therapy. Herein, the latest SHTS-based nanomaterials are summarized and discussed in detail. In addition, therapeutic strategies mediated by endogenous H2S as a trigger or exogenous H2S delivery are also included. A comprehensive understanding of the current status of SHTS-based strategies will greatly facilitate innovation in this field. Lastly, the challenges and key issues related to the design and development of SHTS-based nanomaterials (e.g., morphology, surface modification, therapeutic strategies, appropriate application, and selection of nanomaterials) are outlined.

Formation or Cleavage of Rings via Sulfide-Mediated Reduction Offers Background-Free Detection of Sulfide

A set of three highly selective probes for sulfide detection has been developed. Two novel mechanistic strategies for the detection, including (a) transformation of a pro-fluorophore into an active fluorophore and (b) destruction of a fused ring to activate a fluorophore, have been explored. The structural features of the probes including azido groups ("active" and "latent") and leaving groups (with or without being attached to the fluorophore) have been investigated. During the course of the mechanistic studies, the single-crystal structures of all the probes and the products were obtained. One of the probes proved to be superior in terms of its ability to detect sulfide in pure water via an in situ formation of a fluorophore from a nonfluorescent precursor. These cheap and easy-to-prepare probes offer practical applications of sulfide recognition in environmental water samples and in the ovaries of fruit flies. A detection and quantification method using one of these probes and analysis with a smartphone enabled nonspecialists to detect sulfide reliably.

Perylenequinone-based "turn on" fluorescent probe for hydrogen sulfide with high sensitivity in living cells

Hydrogen sulfide (H₂S) is a kind of gaseous signal molecule in many physiological processes. In order to detect H₂S, a novel "turn on" fluorescent probe 6,12-dihydroxyperylene-1,7-dione (DPD) was designed and synthesized. The probe DPD is fluorescence silence, while the addition of H₂S induces an obvious green fluorescence with an obvious color change from dark blue to yellow-green. The probe shows excellent selectivity, fast response (2.5min) and linear curve (0-90μM) in wide effective pH range (4-10). Competition experiments are also revealed in corresponding studies and the detection limit is 3.6μM. The response mechanism is proved to be the reduction of the probe by H₂S, which is confirmed by ¹H NMR. Furthermore, through the fluorescence turn-on signal toward H₂S in Hela cells, probe DPD was successfully applied to monitor H₂S in living Hela cells.

A Review of Hydrogen Sulfide Synthesis, Metabolism, and Measurement: Is Modulation of Hydrogen Sulfide a Novel Therapeutic for Cancer?

Significance: Hydrogen sulfide (H2S) has been recognized as the third gaseous transmitter alongside nitric oxide and carbon monoxide. In the past decade, numerous studies have demonstrated an active role of H2S in the context of cancer biology. Recent Advances: The three H2S-producing enzymes, namely cystathionine γ-lyase (CSE), cystathionine β-synthase (CBS), and 3-mercaptopyruvate sulfurtransferase (3MST), have been found to be highly expressed in numerous types of cancer. Moreover, inhibition of CBS has shown anti-tumor activity, particularly in colon cancer, ovarian cancer, and breast cancer, whereas the consequence of CSE or 3MST inhibition remains largely unexplored in cancer cells. Intriguingly, H2S donation at high amounts or a long time duration has also been observed to induce cancer cell apoptosis in vitro and in vivo while sparing noncancerous fibroblast cells. Therefore, a bell-shaped model has been proposed to explain the role of H2S in cancer development. Specifically, endogenous H2S or a relatively low level of exogenous H2S may exhibit a pro-cancer effect, whereas exposure to H2S at a higher amount or for a long period may lead to cancer cell death. This indicates that inhibition of H2S biosynthesis and H2S supplementation serve as two distinct ways for cancer treatment. This paradoxical role of H2S has stimulated the enthusiasm for the development of novel CBS inhibitors, H2S donors, and H2S-releasing hybrids. Critical Issues: A clear relationship between H2S level and cancer progression remains lacking. The possibility that the altered levels of these byproducts have influenced the cell viability of cancer cells has not been excluded in previous studies when modulating H2S producing enzymes. Future Directions: The consequence of CSE or 3MST inhibition in cancer cells need to be examined in the future. Better portrayal of the crosstalk among these gaseous transmitters may not only lead to an in-depth understanding of cancer progression but also shed light on novel strategies for cancer therapy.

A novel water-soluble fluorescence probe based on ICT lighten for detecting hydrogen sulfide and its application in bioimaging

Endogenous H₂S, considered to be involved in many physiological processes, has attracted more attention in fluorescence detection and bioimaging. Therefore, it is necessary to design probes with good biocompatibility and high bioavailability. In this study, a novel fluorescent probe, QN-1, based on azide group and quinoline derivatives was developed for detecting H₂S. QN-1 can detect H₂S specifically in aqueous phase, which indicated QN-1 has excellent water solubility. Besides, QN-1 shows excellent properties of higher selectivity and 11-fold fluorescence enhancement at 533 nm. Therefore, QN-1 with excellent properties can be used for cell imaging.

A fluorescent probe based on aggregation-induced emission for hydrogen sulfide-specific assaying in food and biological systems

An AIE-based fluorescent probe was developed for monitoring food spoilage via its response toward hydrogen sulfide.

Reversible Detection and Quantification of Hydrogen Sulfide by Fluorescence Using the Hemoglobin I from Lucina pectinata

A new detection system for the endogenous gaseous transmitter and environmental pollutant hydrogen sulfide is presented. It is based on the modulation of the fluorescence spectrum of a coumarin dye by the absorption spectrum of the recombinant hemoglobin I from clam Lucina pectinata upon coordination of the analyte. While we establish that the reported affinity of rHbI for H₂S has been overestimated, the association of the protein with an appropriate fluorophore allows fast, easy, and reversible detection and quantification of hydrogen sulfide in buffer as well as biological fluids such as human plasma, with a quantification limit around 200 nM at pH 7.4.

Salivary Hydrogen Sulfide Measured with a New Highly Sensitive Self-Immolative Coumarin-Based Fluorescent Probe

Ample evidence suggests that H₂S is an important biological mediator, produced by endogenous enzymes and microbiota. So far, several techniques including colorimetric methods, electrochemical analysis and sulfide precipitation have been developed for H₂S detection. These methods provide sensitive detection, however, they are destructive for tissues and require tedious sequences of preparation steps for the analyzed samples. Here, we report synthesis of a new fluorescent probe for H₂S detection, 4-methyl-2-oxo-2H-chromen-7-yl 5-azidopentanoate (1). The design of 1 is based on combination of two strategies for H₂S detection, i.e., reduction of an azido group to an amine in the presence of H₂S and intramolecular lactamization. Finally, we measured salivary H₂S concentration in healthy, 18–40-year-old volunteers immediately after obtaining specimens. The newly developed self-immolative coumarin-based fluorescence probe (C₁₅H₁₅N₃O₄) showed high sensitivity to H₂S detection in both sodium phosphate buffer at physiological pH and in saliva. Salivary H₂S concentration in healthy volunteers was within a range of 1.641–7.124 μM.

Selective Detection of H2S by Copper Complex Embedded in Vesicles through Metal Indicator Displacement Approach

A new approach for the detection of hydrogen sulfide (H₂S) was constructed within vesicles comprising phospholipids and amphiphilic copper complex as receptor. 1,2-Distearoyl- sn-glycero-3-phosphocholine (DSPC) vesicles with embedded metal complex receptor (1.Cu) sites have been prepared. The vesicles selectively respond to H₂S in a buffered solution and show colorimetric as well as spectral transformation. Other analytes such as reactive sulfur species, reactive nitrogen species, biological phosphates, and other anions failed to induce changes. The H₂S detection is established through a metal indicator displacement (MIDA) process, where Eosin-Y (EY) was employed as an indicator. Fluorescence, UV-vis spectroscopy, and the naked eye as the signal readout studies confirm the high selectivity, sensitivity, and lower detection limit of the vesicular receptor. The application of vesicular receptors for real sample analysis was also confirmed by fluorescence live cell imaging.

Chemically reversible binding of H2S to a zinc porphyrin complex: towards implementation of a reversible sensor via a "coordinative-based approach"

Binding of hydrogen sulfide (H₂S) to a zinc porphyrin complex and the stabilization of the related zinc hydrosulfido adduct are explored. High-resolution MALDI Fourier transform ion cyclotron resonance mass spectrometry (HR MALDI-FT-ICR) and ¹H NMR experiments provide evidence that HS^- coordination occurs at the zinc centre. The coordination of HS^- occurs in a reversible manner and modulates fluorescence emission of a tetra(N-methylpyridyl)porphine zinc complex (TMPyPZn). The results highlight the potential of TMPyPZn and related systems for the implementation of fast and simple H₂S sensors via a coordinative-based approach.

"Turn-on" fluorescent probe for detection of H2S and its applications in bioimaging

A novel fluorescent probe (named YQ-1) containing disulfide-bond coumarin derivative was developed for H₂S. In response to H₂S, YQ-1 showed remarkable fluorescent emission enhancement at 462nm. Besides, YQ-1 exhibited higher selectivity, faster response rate, low cytotoxicity and low detection limit (0.052μM). Further, YQ-1 was used to detect the presence of H₂S level in living A549 cells, indicating YQ-1 has good membrane permeability and fluorescence properties.

Reaction-based ratiometric fluorescent probe for selective recognition of sulfide anions with a large Stokes shift through switching on ESIPT

Ratiometric fluorescent probe BNPT has been synthesized and characterized for S²⁻ sensing via ESIPT mechanism.

A multi-analyte responsive chemosensor vanilinyl Schiff base: fluorogenic sensing of Zn(ii), Cd(ii) and I−

A single fluorescence probe recognizes multiple ions and grabs the great attention of scientists.

Detection of sulfide ion and gaseous H2S using a series of pyridine-2,6-dicarboxamide based scaffolds

This work presents a series of pyridine-2,6-dicarboxamide based scaffolds with different appendages and their roles as chemosensors for the selective detection of S²⁻ ion, as well as gaseous H₂S, in primarily aqueous media.

Cu2+-Mediated turn-on fluorescence assay for sulfide ions using glutathione-protected gold nanoclusters: enhanced sensitivity, good reusability, and cell imaging

Cu²⁺-Mediation enables turn-on fluorescence detection of S²⁻using GSH-Au NCs with good sensitivity, reusability, and applicability in cell imaging.

A two-photon fluorescent probe for specific detection of hydrogen sulfide based on a familiar ESIPT fluorophore bearing AIE characteristics

A two-photon fluorescent probe based on an ESIPT fluorophore bearing AIE characteristics was utilized to detect H₂S.

Highly selective turn-on probe for H2S with imaging applications in vitro and in vivo

A pyrene-based chemosensor, PyN3, has been developed as a H₂S turn-on sensor via reduction of azide to amine.

A new ratiometric fluorescent probe for rapid, sensitive and selective detection of endogenous hydrogen sulfide in mitochondria

We have developed a new ratiometric fluorescent probe composed of a coumarin-merocyanine dyad based on the FRET mechanism. The probe showed clear dual-emission signal changes in blue and red spectral windows upon addition of H2S in a dose dependent manner under a single wavelength excitation. The probe targeted mitochondria with high selectivity and sensitivity toward H2S.

Ratiometric QD-FRET Sensing of Aqueous H2S in Vitro

We report a platform for the ratiometric fluorescent sensing of endogenously generated gaseous transmitter H2S in its aqueous form (bisulfide or hydrogen sulfide anion) based on the alteration of Förster resonance energy transfer from an emissive semiconductor quantum dot (QD) donor to a dithiol-linked organic dye acceptor. The disulfide bridge between the two chromophores is cleaved upon exposure to bisulfide, resulting in termination of FRET as the dye diffuses away from the QD. This results in enhanced QD emission and dye quenching. The resulting ratiometric response can be correlated quantitatively to the concentration of bisulfide and was found to have a detection limit as low as 1.36 ± 0.03 μM. The potential for use in biological applications was demonstrated by measuring the response of the QD-based FRET sensor microinjected into live HeLa cells upon extracellular exposure to bisulfide. The methodology used here is built upon a highly multifunctional platform that offers numerous advantages, such as low detection limit, enhanced photochemical stability, and sensing ability within a biological milieu.