A Fluorescent Chemodosimeter for Live-Cell Monitoring of Aqueous Sulfides

A 3,5-dinitropyridin-2yl Substituted Flavonol-based Fluorescent Probe for Rapid Detection of H2S in Water, Foodstuff Samples and Living Cells

A novel flavonol-based fluorescent probe, Fla-DNT, has been synthesized for the rapid and specific detection of H2S. Fla-DNT exhibits excellent selectivity and anti-interference properties, a short response time (4 min), large Stokes shift (138 nm), and low detection limit (1.357 µM). Upon exposure to H2S, Fla-DNT displays a remarkable increase in fluorescence intensity at 542 nm. Meanwhile, the recognizing site of H2S was predicted through Electrostatic potential and ADCH charges calculations, while the sensing mechanism of H2S was determined via HRMS analysis and DFT calculation. More importantly, the probe owes multiple applications, such as a recovery rate ranging from 92.00 to 102.10% for detecting H2S in water samples, and it can be fabricated into fluorescent strips to track H2S production during food spoilage by tracking color changes, thereby enabling real-time monitoring of food freshness. The bioimaging experiments demonstrate the capability of Fla-DNT to detect both endogenous and exogenous H2S in living cells. These results provide a reliable method and idea for H2S detection in complex environments.

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.

A Portable Array Visualization Device Integrating Sample Preparation and Detection All-in-One for the On-Site Analysis of Complex Samples

A gas membrane separation/array fluorescence visualization (GMS/AFV) device is developed by integrating hydrazine-based carbonized copolymer dots (PD-N2H4) for visual on-site analysis. The novel PD-N2H4 was synthesized using a "polymer template" approach, exhibiting strong blue fluorescence capable of visual sensing. The GMS/AFV device integrates sample preparation and detection all-in-one, consisting of a smartphone, a sample pretreatment system, and an optical system. In the detection procedure, the samples will be treated in the sample pretreatment system to create volatile gases. Therefore, any gas samples as well as solid and liquid samples that potentially produce volatile gases can be visually detected on-site by the device. H2S was utilized as a model analyte to test the practicality of the GMS/AFV device. The entire analysis can be finished in 3 min, and the limit of detection of H2S is as low as 3.4 μg/L. Surprisingly, the device is also capable of high-throughput sample detection, which can process 48 samples simultaneously in about 20 min. The device offers a quick, easy, cheap, and environmentally friendly way to analyze volatile gases, and it creates new opportunities for on-site detection of complex samples.

A Highly Selective Fluorescent Probe for Imaging Hydrogen Sulfide in Living HeLa Cells

As an important endogenous gasotransmitter, hydrogen sulfide (H2S) has been implicated with a variety of biological processes and has attracted more and more attention for its key role in a wide range of pathological processes. However, lacking tools for H2S-specific in situ detection, the changes of endogenous H2S levels in the pathological progression of diseases are still unclear. In this work, a turn-on fluorescent probe (BF2-DBS) has been designed and synthesized by two-step reactions using 4-diethylaminosalicylaldehyde and 1,4-dimethylpyridinium iodide as raw materials. Probe BF2-DBS displays high selectivity and sensitivity to H2S with a large Stokes shift and good anti-interference ability. The practical application of probe BF2-DBS to detect endogenous H2S was evaluated in living HeLa cells.

A BODIPY-based fluorescent chemosensor with 2, 6-substitution for visual and highly selective detection of S2

BODIPY derivatives have often been employed as fluorescent sensors to probe toxic ions in environment and living systems, such as sulfide ion (S^2-). Whilst many structure modifications have been exploited on groups at the 3, 5, 8-positions, there are quite few examples on tailoring the 2,6-substituents for chemosensor investigations. Herein, we design and synthesize a 2,6-substituted BODIPY molecule, LM-BDP, to use as a fluorescent probe for detecting S^2- in aqueous media. The electronic and crystal structures of the probe are studied by density functional theory (DFT) calculations and single-crystal X-ray diffraction analysis. Spectroscopy investigations are performed in a variety of conditions, showing that LM-BDP exhibits a noticeable color change from pink to dark red and a fluorescence shift from yellow to pink channel with decreased intensity upon addition of S^2-. The selectivity and sensitivity measurements show that LM-BDP can only response to S^2- with a detection limit of 0.29 μM in less than 100 s. The remarkable contrast in fluorescence images in test-stripe and RAW 264.7 cell experiments indicates that the probe is a proper candidate for the application in detecting exogenous S^2-.

Gold Nanocluster-Based Ratiometric Probe with Surface Structure Regulation-Triggered Sensing of Hydrogen Sulfide in Living Organisms

The development of reliable probes for in vivo detection of hydrogen sulfide (H₂S) with high sensitivity and selectivity is of great significance due to its key roles in many pathological and physiological processes. Herein, it was found that H₂S could finely regulate surface structure of gold nanoclusters (AuNCs) through reduction of surface Au(I)-ligand motifs and further quench their fluorescence by a two-stage kinetic reaction process. Stage I showed the H₂S-assisted surface Au(I)-ligand reduction and Au(0) core growth with a rapid fluorescence decrease; stage II showed the surface structure optimization and reconstruction with a relatively slow fluorescence quenching. By virtue of the excellent fluorescence response of AuNCs to H₂S, a novel ratiometric fluorescence probe (RBDA) for sensing H₂S was designed through electrostatic attraction-induced fluorescence resonance energy transfer (FRET) between AuNCs and rhodamine B. The probe was facilely prepared, showing a straightforward, rapid ratiometric fluorescence response to H₂S with built-in self-calibration. It presented the high detection sensitivity with a detection limit (LOD) of 56 nM and an excellent sensing selectivity for H₂S over various other biological species. The probe was demonstrated to possess high biostability, low cytotoxicity, good cell and issue penetrability, and favorable biocompatibility. It realizes successful monitoring of both exogenous and endogenous H₂S levels in living cells and zebrafish.

A highly sensitive and selective fluorescence turn-on probe for the sensing of H2S in vitro and in vivo

A fluorescence turn-on probe, 2-butyl-1,3-dioxo-2,3-dihydro-1H-benzo[de]isoquinolin-6-yl 2,4-dinitrobenzenesulfonate (NT-SH), has been constructed for sensing of hydrogen sulfide (H₂S). NT-SH exhibited excellent detection performance including favorable water solubility, low fluorescence background, high enhancement (45-fold), large linear response range (0-50 μM) and low detection limit (80.01 nM) for H₂S in aqueous. In addition, the response mechanism of NT-SH for H₂S was confirmed by the theoretical calculation and mass spectral analysis. More importantly, the imaging experiments of H₂S in vitro and in vivo confirmed that NT-SH had low cytotoxicity, and favorable biocompatibility. In addition, it illustrated that NT-SH was able to detected exogenous H₂S in living cells and zebrafish. These results suggested that NT-SH can be act as a potential molecular tool for detecting of H₂S in aqueous solution, in vitro and in vivo.

Optically superior fluorescent probes for selective imaging of cells, tumors, and reactive chemical species

Fluorescent chemical probes have become powerful tools to study biological events in living cells. They provide a great opportunity to quantitatively and qualitatively analyze the physiological and biochemical properties of living cells in real time. The ability of researchers to manipulate these probes for a desired specific purpose has turned many heads in the scientific community. Despite a slow start, fluorescent probe research has seen exponential growth over the last decade in the world. This change required some adventurous and creative scientists from different fields-like biology, medicine, and chemistry-to come together to facilitate the constant expansion of this field. This review article introduces some fundamental concepts related to fluorescent probe designing and development. It also summarizes various fluorescent probes with superior optical properties used in fields like cell biology, cellular imaging, medical research, and cancer diagnosis. It is hoped that this article will encourage more young and creative scientists to contribute their talents to this field.

Rapid and visual detection of Cd2+ based on aza-BODIPY near infrared dye and its application in real and biological samples for environmental contamination screening

Cadmium highly toxic and hazardous, and it can adversely affect human health leading to serious disorders. Herein, a water-soluble near-infrared sensor based on aza-BODIPY (1) was developed for dual determination of Cd²⁺ in environmental and biological media. This sensor exhibited color change from colorless to green along with a fluorescence enhancement in the near-infrared (NIR) region via photoinduced electron transfer (PET) after complexation with Cd²⁺. Sensor 1 can be employed in aqueous media at physiological pH for quantitative monitoring. It shows rapid response with high sensitivity (detection limit of 2.8 ppb; linear correlation over [Cd²⁺] 1.33 - 6.67 µM) and selectivity over potentially interfering ions. NIR sensor 1 can be used to determine [Cd²⁺] in living cells and environmental samples.

Development of a piperazinyl-NBD-based fluorescent probe and its dual-channel detection for hydrogen sulfide

To selectively detect H₂S based on the thiolysis reaction of 7-nitro-1,2,3-benzoxadiazole (NBD), amines attracted increasing attention since NBD amine is regarded as a new H₂S reaction site. Herein, a novel fluorescent probe, triphenylamine piperazine NBD (TPA-Pz-NBD), was developed. The results showed that it exhibited high selectivity towards H₂S via fluorescence spectroscopy and solution color. Furthermore, TPA-Pz-NBD not only detected H₂S by a dual-channel, turn-on fluorescence signal at 500 nm and turn-off fluorescence signal at 545 nm, respectively, but also displayed a wide detection range of 0-125 μM. In addition, living cell imaging results indicated that TPA-Pz-NBD holds potential for the detection of intracellular H₂S.

A cancer cell-specific benzoxadiazole-based fluorescent probe for hydrogen sulfide detection in mitochondria

The present work describes the design and biological applications of a novel colorimetric and fluorescence turn-on probe for hydrosulfide detection. The probe was designed to introduce hemicyanine as the fluorescent skeleton and 7-nitro-1,2,3-benzoxadiazole as the recognition site. The optical properties and responses of the probe towards HS^-, anions and some biothiols indicate an impressively high selectivity of the probe towards HS^- such that it can be effectively used as an indicator for monitoring the level of HS^- in living cells. In biological experiments using the probe, the H₂S levels are found to be higher in cancer cells than in normal cells. In addition, the probe is shown to specifically and rapidly detect endogenous H₂S, which is produced primarily in the mitochondria of cancer cells, as demonstrated by a co-localization experiment using specific trackers for the detection of cellular organelles in pharmacological inhibition or stimulation studies, without any significant cytotoxic effects. Thus, the results of the chemical and biological experiments described herein demonstrate the potential of this novel probe to specifically, safely, and rapidly detect H₂S to distinguish cancer cells from normal cells by targeting it specifically in mitochondria.

A highly efficient yet stable salamo-type fluorescent chemosensor with multiple responses to Cu2+ and S2−

A new salamo-type compound H3L has been synthesized, and exploited as a chemosensor with multiple responses to Cu2+ and S2−. The crystal structure of the Cu(ii)  complex has been determined by X-ray crystallographic analysis.

A high-efficiency salamo-based copper(ii) complex double-channel fluorescent probe

In this paper, a salamo-based copper(ii) complex probe L-Cu2+ was synthesized, which combined with copper(ii) ions to form L-Cu2+ for the detection of S2- and had a good fluorescence chemical response. Through spectral analysis, we found that S2- could be identified with high sensitivity and selectivity in the presence of various anions and could be used for the detection of S2- by the naked eye. With the addition of S2-, the solution color changed from colorless to bright yellow. UV absorption, fluorescence and other characterization methods were carried out, and the mechanism of action was determined. In addition, we performed a visual inspection of H2S gas, and the probe L-Cu2+ could detect S2- in the gas molecules, revealing its potential application value in biology and medicine.

Chromophore-Modified Highly Selective Ratiometric Upconversion Nanoprobes for Detection of ONOO- -Related Hepatotoxicity In Vivo

Acute hepatitis is a major problem affecting public health and has attracted more and more attention. Generally, as the standard means, blood tests are taken for evaluating hepatitis. However, such tests fail to accurately reflect the level of hepatitis in vivo. Herein, two highly selective ratiometric fluorescent probes are designed to track peroxynitrite (ONOO^- ) as the hepatitis indicator, and further evaluate acute liver injury in vivo through dye-grafted upconversion nanoparticles (UCNPs). Specifically, upconversion luminescence of nanoprobes at 540 or 660 nm can be quenched by the designed and synthesized chromophore E-CC or H-CC, that can be destroyed by ONOO^- via energy transfer (ET) process, while the upconversion luminescence intensity at 810 nm remains the same. Thus, the developed nanoprobes can be used for ratiometric detection (I₅₄₀ /I₆₆₀ or I₆₆₀ /I₈₁₀ ) of ONOO^- . Moreover, the developed near infrared ratiometric nanoprobes can highly selectively detect ONOO^- , which can eliminate the interference of HOCl and SO₃^2- . Finally, it is demonstrated that this highly selective ratiometric nanosystem can achieve effective detection of ONOO^- in living cells and CCl₄ -induced acute liver injury models. It provides some reference value for clinical detection of hepatotoxicity.

Reaction-Based Fluorescent Probes for the Detection and Imaging of Reactive Oxygen, Nitrogen, and Sulfur Species

This Account describes a range of strategies for the development of fluorescent probes for detecting reactive oxygen species (ROS), reactive nitrogen species (RNS), and reactive (redox-active) sulfur species (RSS). Many ROS/RNS have been implicated in pathological processes such as Alzheimer's disease, cancer, diabetes mellitus, cardiovascular disease, and aging, while many RSS play important roles in maintaining redox homeostasis, serving as antioxidants and acting as free radical scavengers. Fluorescence-based systems have emerged as one of the best ways to monitor the concentrations and locations of these often very short lived species. Because of the high levels of sensitivity and in particular their ability to be used for temporal and spatial sampling for in vivo imaging applications. As a direct result, there has been a huge surge in the development of fluorescent probes for sensitive and selective detection of ROS, RNS, and RSS within cellular environments. However, cellular environments are extremely complex, often with more than one species involved in a given biochemical process. As a result, there has been a rise in the development of dual-responsive fluorescent probes (AND-logic probes) that can monitor the presence of more than one species in a biological environment. Our aim with this Account is to introduce the fluorescent probes that we have developed for in vitro and in vivo measurement of ROS, RNS, and RSS. Fluorescence-based sensing mechanisms used in the construction of the probes include photoinduced electron transfer, intramolecular charge transfer, excited-state intramolecular proton transfer (ESIPT), and fluorescence resonance energy transfer. In particular, probes for hydrogen peroxide, hypochlorous acid, superoxide, peroxynitrite, glutathione, cysteine, homocysteine, and hydrogen sulfide are discussed. In addition, we describe the development of AND-logic-based systems capable of detecting two species, such as peroxynitrite and glutathione. One of the most interesting advances contained in this Account is our extension of indicator displacement assays (IDAs) to reaction-based indicator displacement assays (RIAs). In an IDA system, an indicator is allowed to bind reversibly to a receptor. Then a competitive analyte is introduced into the system, resulting in displacement of the indicator from the host, which in turn modulates the optical signal. With an RIA-based system, the indicator is cleaved from a preformed receptor-indicator complex rather than being displaced by the analyte. Nevertheless, without a doubt the most significant result contained in this Account is the use of an ESIPT-based probe for the simultaneous sensing of fibrous proteins/peptides AND environmental ROS/RNS.

Molecular engineering of a colorimetric two-photon fluorescent probe for visualizing H2S level in lysosome and tumor

As a multifunctional signaling molecule, hydrogen sulfide (H₂S) plays an essential role in diverse physiological and pathological processes. The two-photon fluorescence probes detecting H₂S selectively in vivo could be useful tools to better study the mechanism of diseases. Then, an efficient two-photon lysosome-specific probe 1 has been developed to detect endogenous H₂S in living cells and mice. Probe 1 displays excellent properties with 28-fold fluorescence enhancement, marked color changes in naked-eye and fluorescence, high selectivity and sensitivity, and low detection limit (0.22 μM) to H₂S. These remarkable properties of probe 1 enable its practical applications in detecting H₂S in environment (wastewater) and food (beer). Moreover, as a two-photon probe under near infrared excitation at 790 nm, probe 1 can monitor the level changes of endogenous H₂S of lysosome and tumor in living system with good membrane permeability and high imaging resolution. Specially, the probe detecting H₂S distribution in lysosome could provide more evidences to explain the association of target-organelle and H₂S.

Superb-selective chemodosimetric signaling of sulfide in the absence and in the presence of CT-DNA and imaging in living cells by a plant alkaloid berberine analogue

New berberine analogue (BER-S), as a colorimetric probe in the absence of DNA and turn-on fluorometric probe in the presence of DNA towards S²⁻ detection is reported.

Tuning lipophilicity for optimizing the H2S sensing performance of coumarin–merocyanine derivatives

In this paper, a series of coumarin-merocyanine derivatives with different lipophilicities were synthesized to investigate the relationship between structural lipophilicity and reactivity as well as mitochondrial targeting ability.

An etching based fluorescent probe for sensitive detection of hydrogen sulfide in cells

Hydrogen sulfide (H₂S) is one of the most crucial gas signaling agents that mediate many physiological and pathological processes. However, rapid high-efficiency detection and imaging of H₂S in living cells is very challenging. Herein we reported a simple fluorescent nanoprobe using FAM-DNA/AgNP nanocomposites for fast and sensitive H₂S detection based on surface silver displacement. In contrast to the conventional principles for fluorescence turn-on analyte detection, the present work demonstrated a sensitive and selective AgNP based optosensor for the assay of H₂S. Compared with the majority of the reported H₂S probes, complex synthesis procedures and costly equipment are not involved in this assay.

Embedding Nanocluster in MOF via Crystalline Ion-Triggered Growth Strategy for Improved Emission and Selective Sensing

Metal-organic frameworks (MOFs) containing metal nanoclusters (NCs) display great potentials, but the fabrication faces challenges because of the serious agglomeration of NCs during the MOF growth. We report a crystalline ion-triggered growth strategy for embedding AuNCs in ZIF-8. As control, when the encapsulation was triggered with other metal ions (e.g., Ca²⁺, Pb²⁺, Cd²⁺, Na⁺, Fe³⁺, Cu²⁺, and Ni²⁺), the AuNCs failed to be encapsulated. The quantum yields and lifetime of AuNCs were greatly enhanced after embedding in ZIF-8. The AuNCs@ZIF-8 were then successfully applied for the selective sensing of H₂S both in liquid and gas phases. This crystalline ion-triggered growth strategy was easily extended to other systems, such as AgNCs@ZIF-8 and AuNCs@ZIF-67, indicating the general adaptability of this design protocol.

Rosamine with pyronine-pyridinium skeleton: unique mitochondrial targetable structure for fluorescent probes

Rosamine-based probes (1a–b) with pyronine-pyridinium skeleton served as mitochondrial targetable probes for detecting independent species (H₂O₂ and H₂S).

Real-Time Monitoring of Endogenous Cysteine Levels In Vivo by near-Infrared Turn-on Fluorescent Probe with Large Stokes Shift

Cysteine (Cys), as an important biothiol, plays a major role in many physiological processes like protein synthesis, detoxification and metabolism, and also is closely associated with a variety of diseases; thus the design of novel highly selective and sensitive near-infrared (NIR) fluorescent probes for Cys detection in vivo is of great significance. Herein, we report a selective and sensitive NIR turn-on fluorescent probe (CP-NIR) with large Stokes shift for detecting Cys in vivo. Upon addition of Cys to the solution of the probe, it is absorption wavelength shifts from 550 to 600 nm, accompanying with an obvious enhancement of NIR fluorescence emission centering around 760 nm. This Michael-addition reaction-based probe shows a large Stokes shift (160 nm), low detection limit (48 nM), fast response time, and low toxicity. Moreover, this novel NIR probe with good cell permeability was successfully applied to monitoring endogenous Cys in living cells and in a mouse model.

Fine Regulation of Porous Architectures of Core-Shell Silica Nanocomposites Offers Robust Nanoprobes with Accelerated Responsiveness

Probes bearing good aqueous solubility and biocompatibility as well as fast response can serve as ideal tools for evaluating the underlying molecular mechanism of endogenous production of H₂S caused by drugs; however, they are still lacking but highly desirable. Here, we demonstrate a novel strategy for constructing highly efficient H₂S nanoprobes through locking Förster resonance energy transfer borondipyrromethene (BODIPY) pairs in water-dispersible core-shell silica nanoparticles. Importantly, these nanocomposites can effectively confine complementary guests within the same cores due to the existence of a shield, thus guaranteeing efficient Förster resonance energy transfer. Interestingly, the interior microenvironment of such nanoparticles could be tuned by silylation agents. In this way, an ideal probe for rapid and ratiometric detection of H₂S within 15 s is established by optimizing the amount of silylation agent with a polar organic group. Obviously, the silylation agents are explored to serve as a platform not only for establishment of robust structures but also for optimizing the microenvironment of the interior to afford an ideal probe. These silica nanocomposites have also been successfully employed in disclosing the endogenous production of H₂S induced by estrogen in cardiomyocytes.

A turn-on endoplasmic reticulum-targeted two-photon fluorescent probe for hydrogen sulfide and bio-imaging applications in living cells, tissues, and zebrafish

As one of the important gas signal molecules, hydrogen sulfide (H₂S) is associated with many important physiological processes in living organisms. Organelles, especially endoplasmic reticulum (ER), play a crucial role in the cell metabolism. Accordingly, the detection of H₂S in the ER is of high interest. Toward this goal, we have described the development of the first ER-targeted fluorescent H₂S probe (Na-H ₂ S-ER). The new probe exhibited favorable features, such as a large turn-on fluorescence signal (45-fold fluorescence enhancement), high sensitivity and selectivity. The probe was successfully employed for imaging exogenous and endogenous H₂S in the living HeLa cells. Significantly, the new probe Na-H ₂ S-ER was employed to visualize H₂S in the ER of living cells for the first time. In addition, the probe was also successfully used for imaging H₂S in the living tissues up to a depth of 100 μm and in the living zebrafish.

Multifunctional nanoprobes for both fluorescence and 19F magnetic resonance imaging

Fluorescence is widely used for cell imaging due to its high sensitivity and rich color choice but limited for in vivo imaging because of its low light penetration. Meanwhile, magnetic resonance imaging (MRI) is widely applied for in vivo diagnosis but not suitable for cell imaging because of its low resolution. Compared to ¹H-MRI, ¹⁹F-MRI is more suitable for clinical application due to its high sensitivity but fabricating ¹⁹F-MRI probes is a great challenge. Therefore, it is highly desirable to develop a dual-modal imaging probe for both cell fluorescence imaging and in vivo¹⁹F-MRI with high sensitivity and deep penetration. In this study, ¹⁹F moiety loaded nanocomposites with an organic fluorescent core were successfully prepared via a facile strategy by encapsulating organic dyes with oleylamine-functionalized polysuccinimide and 1H,1H,2H,2H-perfluorodecyltriethoxysilane (PDTES). The aggregation of organic fluorescent dyes in the core results in significant fluorescence for optical imaging, while the ¹⁹F moieties on PDTES allow for simultaneous ¹⁹F MRI. Moreover, the nanocomposites exhibited high water dispersibility and excellent biocompatibility. These properties make them promising for both cell imaging and in vivo imaging applications.

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.

A novel two-photon fluorescent probe for hydrogen sulfide in living cells using an acedan–NBD amine dyad based on FRET process with high selectivity and sensitivity

The first NBD amine based two-photon fluorescence probe L using a FRET strategy was developed for the H₂S detecting in vitro and in vivo. The probe L not only afforded high selectivity and sensitivity for H₂S detecting, but also dispalyed a linear response to H₂S with a low detection limit 24 nM.

Photoacoustic probes for real-time tracking of endogenous H2S in living mice

H₂S is a key chemical mediator that exerts a vital role in diverse physiological and pathological processes. However, in vivo tracking of endogenous H₂S generation still remains difficult due to the lack of reliable analytical methods. Herein, we present the first example of activatable photoacoustic probes for real-time imaging of H₂S in living mice through the full utilization of the superiority of photoacoustic imaging modality at fine spatial resolution during deep tissue penetration. The designed probe can generate high NIR absorption at 780 nm in the presence of H₂S, thus producing a strong photoacoustic signal output in the NIR region. Furthermore, this probe exhibits extremely fast and highly selective responsiveness, good water-solubility and excellent biocompatibility. In light of these outstanding features, this probe realizes the direct photoacoustic trapping of endogenous H₂S generation in a HCT116 tumor-bearing mouse model. These preliminary imaging studies show that HCT116 colon tumors exhibit CBS upregulation activity, resulting in an increased rate of H₂S generation.

Novel Fluorescein-Based Fluorescent Probe for Detecting H2S and Its Real Applications in Blood Plasma and Biological Imaging

A broad-spectrum fluorescent probe, which can be applied to monitoring H₂S in various biological systems, has been rationally designed and synthesized. This specific probe was applied to localize the endogenous H₂S in living Raw264.7 macrophage cells, HepG2 cells, and H9C2 cells. At the same time, the probe has successfully visualized CBS- and CSE-induced endogenous H₂S production and monitored CBS and CSE activity in H9C2 cells. This probe could serve as a powerful molecular imaging tool to further explore the physiological function and the molecular mechanisms of endogenous H₂S in living animal systems.

Reactivity, Selectivity, and Stability in Sulfenic Acid Detection: A Comparative Study of Nucleophilic and Electrophilic Probes

The comparative reaction efficiencies of currently used nucleophilic and electrophilic probes toward cysteine sulfenic acid have been thoroughly evaluated in two different settings-(i) a small molecule dipeptide based model and (ii) a recombinant protein model. We further evaluated the stability of corresponding thioether and sulfoxide adducts under reducing conditions which are commonly encountered during proteomic protocols and in cell analysis. Powered by the development of new cyclic and linear C-nucleophiles, the unsurpassed efficiency in the capture of sulfenic acid under competitive conditions is achieved and thus holds great promise as highly potent tools for activity-based sulfenome profiling.