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

Construction of a coumarin-based fluorescent probe for accurately visualizing hydrogen sulfide in live cells and zebrafish

Hydrogen sulfide (H2S), an important gas signaling molecule, is a regulator of many physiological processes, and its abnormal levels are closely related to the onset and progression of disease. It is vital to develop methods for specific tracking of H2S in clinical diagnosis and treatment. In this study, we designed an ultrasensitive and highly stable coumarin-based fluorescent probe Cou-H2S. Through the H2S-initiated tandem reaction, Cou-H2S successfully achieved highly selective and super-fast detection of H2S. Cou-H2S was successfully applied to the monitoring of endogenous and exogenous H2S at the cellular level and verified the validity of the detection of H2S in the LPS-induced zebrafish model. Therefore, Cou-H2S might provide new insights into the study of H2S-related diseases.

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 structural optimized fluorescent probe for monitoring hydrogen sulfide in cells and zebrafish

In this work, we reported a fluorescent probe Fur-SH, a derivative of benzofuranone, which was used to detect H2S in living cells and zebrafish. Based on the three structural characteristics of the probe, the effects of different structural modifications on the optical properties of the fluorophore were compared. Then, the fluorophore Fur-OH was synthesized by modifying diethylamino group with benzofuranone as the main skeleton. With 2,4-dinitrofluorobenzene as the recognition group and diethylamino as the electron donor, the push-pull electron effect occurred with nitro group, which led to fluorescence quenching, and an openable fluorescent probe Fur-SH was formed. The probe Fur-SH (λex = 510 nm; λem = 570 nm) had the advantages of smaller full width at half maxima, rapid response (5 min) and wide pH window. The quantitative properties of the probe were excellent, reaching saturation at 50 equivalents of substrate. The probe Fur-SH showed high sensitivity to H2S, with LOD of 48.9 nM and LOQ of 50 nM. At present, the probe Fur-SH had been applied to fluorescence imaging of MCF-7 cells and zebrafish. By comparing the effects of different structures on the optical properties of fluorophores, this work was expected to be helpful to the development of fluorescent probes in the future.

A dual-responsive fluorescent probe based on cyanine and naphthalimide units for detecting HClO and H2S in living cells

Hypochlorous acid (HClO) and hydrogen sulfide (H2S) play very important roles in both physiological and pathological processes, however, the methods for simultaneously detecting HClO and H2S were rarely reported. Here, a dual-responsive fluorescent probe (CyNa-N3) based on cyanine and naphthalimide dyes was synthesized and investigated. The fluorescence probe showed better sensitivity, high selectivity response to HClO and H2S by red emission and green emission bands, and the limits of detection were 0.17 µM and 0.15 µM respectively. MS (Mass Spectrum) and 1H NMR (Nuclear Magnetic Resonance) confirmed the sensing mechanism of CyNa-N3 detected HClO and H2S, the calculation of density functional theory (DFT) further explained the internal mechanism of spectral change of CyNa-N3. Moreover, CyNa-N3 was successfully applied to image HClO and H2S in living cells, which is beneficial for more efficient application in biological imaging.

Construction of a novel chitosan-based macromolecular nanoprobe for specific fluorescent detection of H2S in live animals

H2S is one of the signal molecules in live organisms and a poisonous gas, which is closely related to our life. The traditional synthetic small molecular organic probes often have the disadvantages of low biocompatibility. In this paper, a fluorescent nanoprobe for detecting H2S in live organisms was constructed based on chitosan. The structure of CH-CN was characterized by infrared spectroscopy, nuclear magnetic resonance, x-ray photoelectron spectroscopy (XPS), XRD and scanning electron microscope (SEM). In the presence of Na2S, the fluorescence intensity at 560 nm was significantly enhanced, and showed high selectivity and sensitivity toward H2S. Based on the good fluorescence response of CH-CN, the probe was also successfully applied to H2S imaging in HepG2 cells and zebrafish. These experimental results indicate that the probe has lower cytotoxicity and excellent stability. The present research shows a typical example of construction of chitosan-based macromolecular fluorescent materials and their bio-imaging application.

HPLC Study of Product Formed in the Reaction of NBD-Derived Fluorescent Probe with Hydrogen Sulfide, Cysteine, N-acetylcysteine, and Glutathione

Hydrogen sulfide (H₂S) and its bioderivatives analogs, such as L-cysteine (L-Cys) and glutathione (GSH), are ubiquitous biological thiols in the physiological and pathological processes of living systems. Their aberrant concentration levels are associated with many diseases. Although several NBD-based fluorescence probes have been developed to detect biological thiols, the HPLC-detection of H₂S, GSH, L-Cys, and N-acetylcysteine-specific products has not been described. Herein, a novel NBD-derived pro-coumarin probe has been synthesized and used to develop a new strategy for the triple mode detection of H₂S and such thiols as GSH, L-Cys, and NAC. Hydrogen sulfide and those biothiols at physiological pH release fluorescent coumarin from the probe and cause a significant fluorescence enhancement at 473 nm. The appropriate NBD-derived product for H₂S, L-Cys, GSH, and NAC has a different color and retention time that allows distinguishing these biological thiols meaning the probe has a great possibility in the biological application. Fluorescent imaging combined with colorimetric and HPLC detection of H₂S/biothiol-specific product(s) brings a potential tool for confirming the presence of biological thiols and determining concentrations in various aqueous biological samples.

Development and application of a novel β-diketone difluoroboron-derivatized fluorescent probe for sensitively detecting H2S

Hydrogen sulfide{Wang, 2018 #4}{Wang, 2018 #4}{Zhong, 2020 #9} (H₂S) is a poisonous and harmful gas molecule. Certain concentrations of H₂S{Liu, 2021 #8} can irritate the eyes, respiratory system, and central nervous system of human beings. Therefore, it was an urgent need for highly selective, anti-interference, and sensitive detection technology for hydrogen sulfide. Herein, a novel "turn-on" fluorescent probe 1-(2-(6,6-dimethylbicyclo[3.1.1]heptyl-2-ene-2-yl))-9-(4-(dimethylaminophenyl))non-1,6,8-triene-3,5-dione boron difluoride complex (MCBF) was designed and synthesized for detecting H₂S sensitively. MCBF displayed a remarkable fluorescence enhancement response to H₂S with a large Stokes shift of 220 nm. The sensitive detection of MCBF towards H₂S owned good selectivity, fast response time (6 min), excellent photostability, and low detection limit (0.44 μM). The sensing mechanism of MCBF towards H₂S was well confirmed by HRMS analysis, ¹H NMR titration, and density functional theory (DFT) calculations. What's more, probe MCBF was successfully applied to detect the contained H₂S in red wine, which showed the potential practicability of MCBF in real samples analysis.

N-quaternization of heterocyclic compound extended the emission to NIR with large Stokes shift and its application in constructing fluorescent probe

This is great significant to establish a method that extends the small molecules fluorescence emission wavelength to the near-infrared region (NIR) for in vivo imaging. Hence, we firstly reported a novel fluorogenic scaffold QOH that could extend its fluorescence wavelength from (λ_em = 555 nm) to NIR (λ_em = 720 nm) with a large Stokes shift (120 nm) by forming its N-quaternization product (QMOH). In addition, the effect of the introduction of substituent at different modification sites and the properties of substituent on the optical properties of QOH were fully discussed by theoretical calculation. To investigate the possibility of QOH as probe construction, the compound Q-SH and QM-R were synthesized and applied to detect H₂S and H₂O₂ in vitro and in vivo, respectively. This study provided an efficient strategy to extend fluorescence emission to NIR and design fluorescence probes with large ratio variation for accurately imaging biomarkers in biological system.