A highly sensitive and responsive fluorescent probe based on 6-azide-chroman dye for detection and imaging of hydrogen sulfide in cells

Multiple Applications of a Novel Fluorescence Probe with Large Stokes Shift and Sensitivity for Rapid H2S Detection

Herein, a novel fluorescence probe Fla-DNP based on flavonol has been designed and synthesized for rapid, specific detection of H2S. With the addition of H2S, Fla-DNP triggered thiolysis and released Fla displaying the "turn-on" fluorescence response at 566 nm, which is consistent with the reaction site predicted by calculating Electrostatic potential and ADCH charges. As an easily available H2S probe, Fla-DNP has the advantages of high selectivity, anti-interference, low detection limit (0.834 μM), short response time (6 min), and large Stokes shift (124 nm). The sensing mechanism of H2S was determined by HRMS analysis and DFT calculation. Moreover, Fla-DNP processes a wide range of multiple applications, including the detection of H2S in environmental water samples with good recovery rates ranging from 89.6% to 102.0%, as well as tracking the production of H2S during food spoilage. Meanwhile, the probe exhibits superior biocompatibility and can not only be available used for H2S detection in living cells but be further designed as an H2S-activated CO photoreleaser, based on which it can be developed as a targeted anti-cancer drug.

PEGylated AIEgens for dual sensing of ATP and H2S and cancer cells photodynamic therapy

Fluorescent sensors have been widely applied for biosensing, but probes for both multiple analytes sensing and photodynamic therapy (PDT) effect are less reported. In this article, we reported three AIE-based probes anchored with different mass-weight polyethylene glycol (PEG) tails, i.e., TPE-PEG160, TPE-PEG350, and TPE-PEG750, for both adenosine-5'-triphosphate (ATP) and hydrogen sulfide (H2S) detection and also cancer cells photodynamic therapy. TPE-PEGns (n = 160, 350 and 750) contain the tetraphenylethylene-based fluorophore core, the pyridinium and amide anion binding sites, the H2S cleavable disulfide bond, and the hydrophilic PEG chain. They exhibit a good amphiphilic property and can self-assemble nona-aggregation with a moderated red emission in an aqueous solution. Importantly, the size of aggregation, photophysical property, sensing ability and photosensitivity of these amphiphilic probes can be controlled by tuning the PEG chain length. Moreover, the selected probe TPE-PEG160 has been successfully used to detect environmental H2S and image ATP levels in living cells, and TPE-PEG750 has been used for photodynamic therapy of tumor cells under light irradiation.

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.

Small Molecule Optical Probes for Detection of H2S in Water Samples: A Review

Hydrogen sulfide (H2S) is closely linked to not only environmental hazards, but also it affects human health due to its toxic nature and the exposure risks associated with several occupational settings. Therefore, detection of this pollutant in water sources has garnered immense importance in the analytical research arena. Several research groups have devoted great efforts to explore the selective as well as sensitive methods to detect H2S concentrations in water. Recent studies describe different strategies for sensing this ubiquitous gas in real-life water samples. Though many of the designed and developed H2S detection approaches based on the use of organic small molecules facilitate qualitative/quantitative detection of the toxic contaminant in water, optical detection has been acknowledged as one of the best, attributed to the simple, highly sensitive, selective, and good repeatability features of the technique. Therefore, this review is an attempt to offer a general perspective of easy-to-use and fast response optical detection techniques for H2S, fluorimetry and colorimetry, over a wide variety of other instrumental platforms. The review affords a concise summary of the various design strategies adopted by various researchers in constructing small organic molecules as H2S sensors and offers insight into their mechanistic pathways. Moreover, it collates the salient aspects of optical detection techniques and highlights the future scope for prospective exploration in this field based on the limitations of the existing H2S probes.

Dual-channel fluorescent probe for discriminative detection of H2S and N2H4: Exploring sensing mechanism and real-time applications

A highly efficient system incorporates the real-time visualization of the two toxic molecules (H2S and N2H4) and the recognition of corresponding transforms using a fluorescent sensor. In this paper, a dual-responsive probe (QS-DNP) based on methylquinolinium-salicyaldehyde-2,4-dinitrophenyl was developed that can simultaneously detect H2S and N2H4 at two independent fluorescent channels without signal crosstalk. QS-DNP showed excellent anti-interference, high selectivity, outstanding water solubility, low LOD values (H2S: 51 nM; N2H4: 40 nM), low cytotoxicity, and mitochondrial localization properties. The 2,4-dinitrophenyl site was sensitive to H2S, and the CC bridge was reactive to N2H4, with strong fluorescence at 680 and 488 nm, respectively. The wavelength gap between these two channels is 192 nm; verify that there is no signal crosstalk throughout detection. By this means, the probe was used to simultaneously detect H2S and N2H4 in real soil samples, food samples, and living cells. The endogenous H2S and N2H4 were monitored in HeLa cells and investigated the mitochondria organelle of living cells with a positive charge on QS-DNP. Overall, all results emphasize that the QS-DNP probe is a powerful tool for the simultaneous detection of H2S and N2H4 and presents a potential new sensing approach.

A near-infrared fluorescent probe for detecting hydrazine metabolized from isoniazid in living cells

Isoniazid is a drug for treating tuberculosis, but hydrazine (N2 H4 ), the major metabolite of isoniazid, can cause hepatotoxicity. Therefore, monitoring the content of N2 H4 in time is of great significance for studying the hepatotoxicity induced by isoniazid. In this study, a near-infrared fluorescent probe (BC-N) was designed and synthesized based on the specific reaction of acetyl ester with N2 H4 . BC-N exhibits excellent selectivity, sensitivity, and biocompatibility. In addition, BC-N is applied in the visualization of N2 H4 produced from isoniazid in living cells and is a potential tool for monitoring hepatotoxicity induced by isoniazid.

Development of a H2S-responsive NIR Fluorescent Probe for H2S Detection and H2S Releasing Monitoring From Prodrug

H2S was deemed as a toxic gradient in the realm of food and environment but plays pivotal pathophysiological roles in organisms. H2S instabilities and disturbances are always responsible for multiple disorders. We fabricated a H2S-responsive NIR fluorescent probe (HT) for H2S detection and evaluation both in vitro and in vivo. HT exhibited rapid H2S response within 5 min, accompanied with visible color change and NIR fluorescence generation, and the fluorescent intensities were linearly correlated with corresponding H2S concentrations. When HT was incubated with A549 cells, the intracellular H2S and H2S fluctuations could be monitored ore rotundo via the responsive fluorescence. Meanwhile, when HT was co-administrated with H2S prodrug ADT-OH, the H2S release from ADT-OH could be visualized and monitored to evaluate its release efficacy.

Sensitive Detection of Various Forms of Hydrogen Sulfide via Highly Selective Naphthalimide-Based Fluorescent Probe

Hydrogen sulfide (H2S) is an important gasotransmitter, but only a few methods are available for real-time detection. Fluorescent probes are attractive tools for biological applications because of their high sensitivity, convenience, rapid implementation, noninvasive monitoring capability, and simplicity in fluorescent imaging of living cells and tissues. Herein, we report on a pro-fluorescent probe, NAP-Py-N3 based on naphthalimide derivative, which was found to show high selectivity toward H2S over various other analytes, including biothiols, making it feasible to detect H2S. After reaction with H2S, this probe showed rapid and significant turn-on green fluorescent enhancement at 553 nm (about 54-fold, k2 = 9.62 M-1s-1), high sensitivity (LOD: 15.5 nM), significant Stokes shift (118 nm), and it was found that the fluorescence quantum yield of fluorescence product can reach 0.36. Moreover, the probe has also been successfully applied to detect the gaseous H2S and to confirm the presence of H2S released from modern organic donors, which in recent years have been commonly used to investigate the role of H2S in biological systems. All the results indicate that this probe is excellent and highly valuable.

A Water-Soluble Hydrogen Sulfide Donor Suppresses the Growth of Hepatocellular Carcinoma via Inhibiting the AKT/GSK-3β/β-Catenin and TGF-β/Smad2/3 Signaling Pathways

Hepatocellular carcinoma (HCC) is a disease with high morbidity, high mortality, and low cure rate. Hyaluronic acid (HA) is widely adopted in tissue engineering and drug delivery. 5-(4-Hydroxyphenyl)-3H-1, 2-dithiol-3-thione (ADT-OH) is one of commonly used H₂S donors. In our previous study, HA-ADT was designed and synthesized via coupling of HA and ADT-OH. In this study, compared with sodium hydrosulfide (NaHS, a fast H₂S-releasing donor) and morpholin-4-ium (4-methoxyphenyl)-morpholin-4-ylsulfanylidenesulfido-λ5-phosphane (GYY4137, a slow H₂S-releasing donor), HA-ADT showed stronger inhibitory effect on the proliferation, migration, invasion, and cell cycle of human HCC cells. HA-ADT promoted apoptosis by suppressing the expressions of phospho (p)-protein kinase B (PKB/AKT), p-glycogen synthase kinase-3β (GSK-3β), p-β-catenin, and also inhibited autophagy via the downregulation of the protein levels of p-Smad2, p-Smad3, and transforming growth factor-β (TGF-β) in human HCC cells. Moreover, HA-ADT inhibited HCC xenograft tumor growth more effectively than both NaHS and GYY4137. Therefore, HA-ADT can suppress the growth of HCC cells by blocking the AKT/GSK-3β/β-catenin and TGF-β/Smad2/3 signaling pathways. HA-ADT and its derivatives may be developed as promising antitumor drugs.

A Cell Trappable Methyl Rhodol-Based Fluorescent Probe for Hydrogen Sulfide Detection

Hydrogen sulfide is a biologically important molecule and developing chemical tools that enable further investigations into the functions of H2 S is essential. Fluorescent turn-on H2 S probes have been developed for use in cellulo and in vivo, but the membrane permeability of these probes can lead to probe leakage and signal attenuation over time. Here we report a cell trappable fluorescent probe for H2 S, CT-MeRhoAz, which is based on a methylrhodolazide scaffold derivatized with an acetoxymethyl ester group. Prior to ester cleavage, the CT-MeRhoAz probe generates a 2500-fold turn-on response to H2 S, which is enhanced to a 3000-fold response for the carboxylic acid form of the probe. Additionally, the probe is highly selective for H2 S over other biologically relevant sulfur, oxygen, and nitrogen-based analytes. Live cell imaging experiments confirmed the biocompatibility of CT-MeRhoAz and also that it is cell trappable, unlike the parent MeRhoAz scaffold.

A super sensitive fluorescent probe for imaging endogenous hydrogen sulfide in living cells

Hydrogen sulfide (H₂S) that typically performs biphasic biological functions in organisms plays an opposite role at the concentrations above or below normal level of the organism. Therefore, it is significant to develop a fluorescent probe with high sensitivity and selectivity and rapid response for the detection of hydrogen sulfide in vivo. The work describes the design and biological applications of a novel turn-on fluorescence probe SS-N₃ in which the quinoline quaternary ammonium salt derivative is introduced as the fluorescent skeleton and azide is employed as the detection group of H₂S. The probe SS-N₃ shows strong fluorescence at 610 nm, as the azide group is reduced to an amino group by H₂S. The probe SS-N₃ shows high selectivity to H₂S than other anions and some biological mercaptans, and strong anti-interference capacity. In addition, the probe SS-N₃ exhibits little cytotoxicity, improved photostability and large Stokes shift (135 nm), as well as can be effectively used as an indicator of H₂S level in living cells.

A near-infrared fluorescent probe based on the hemicyanine skeleton for the detection of hydrogen peroxide in vivo

As a member of the reactive oxygen species, hydrogen peroxide (H₂O₂) plays critical roles in oxidative stress and cell signaling. Intracellular abnormal levels of H₂O₂ production are closely related to many diseases. Therefore, the real-time monitoring of H₂O₂ in the cells is important. In this work, we designed a novel fluorescent probe (Mito-H₂O₂) for the specific detection of H₂O₂ based on the hemicyanine skeleton, with bright near-infrared fluorescence emission. Mito-H₂O₂ displayed fast response, excellent water-solubility and great fluorescence intensity enhancement after the addition of H₂O₂. Furthermore, Mito-H₂O₂ has been successfully applied to image both of the exogenous and endogenous H₂O₂ in cells and mice with negligible cytotoxity.

A covalent modification strategy for di-alkyne tagged metal–organic frameworks to access efficient heterogeneous catalysts toward C–C bond formation

A di-alkyne tagged MOF was proposed to introduce diverse metals, and UiO-66-(alkyne-Co)2 displayed an efficient catalytic performance for the Knoevenagel reaction.

Design and development of selective competitive fluorescent ligands for the detection and visualization of Kv7.2/7.3 in vitro

A series of specific and potent fluorescent ligands were developed for labelling and visualizing Kv7.2/7.3 based molecular rotation restriction. Probes 21b and 24a were found to be safe and convenient...

4-Azidocinnoline-Cinnoline-4-amine Pair as a New Fluorogenic and Fluorochromic Environment-Sensitive Probe

A new type of fluorogenic and fluorochromic probe based on the reduction of weakly fluorescent 4-azido-6-(4-cyanophenyl)cinnoline to the corresponding fluorescent cinnoline-4-amine was developed. We found that the fluorescence of 6-(4-cyanophenyl)cinnoline-4-amine is strongly affected by the nature of the solvent. The fluorogenic effect for the amine was detected in polar solvents with the strongest fluorescence increase in water. The environment-sensitive fluorogenic properties of cinnoline-4-amine in water were explained as a combination of two types of fluorescence mechanisms: aggregation-induced emission (AIE) and excited state intermolecular proton transfer (ESPT). The suitability of an azide-amine pair as a fluorogenic probe was tested using a HepG2 hepatic cancer cell line with detection by fluorescent microscopy, flow cytometry, and HPLC analysis of cells lysates. The results obtained confirm the possibility of the transformation of the azide to amine in cells and the potential applicability of the discovered fluorogenic and fluorochromic probe for different analytical and biological applications in aqueous medium.

Recent progress of graphene oxide-based multifunctional nanomaterials for cancer treatment

Background

In the last decade, graphene oxide-based nanomaterials, such as graphene oxide (GO) and reduced graphene oxide (rGO), have attracted more and more attention in the field of biomedicine. Due to the versatile surface functionalization, ultra-high surface area, and excellent biocompatibility of graphene oxide-based nanomaterials, which hold better promise for potential applications than among other nanomaterials in biomedical fields including drug/gene delivery, biomolecules detection, tissue engineering, especially in cancer treatment.

Results

Here, we review the recent progress of graphene oxide-based multifunctional nanomaterials for cancer treatment. A comprehensive and in-depth depiction of unique property of graphene oxide-based multifunctional nanomaterials is first interpreted, with particular descriptions about the suitability for applying in cancer therapy. Afterward, recently emerging representative applications of graphene oxide-based multifunctional nanomaterials in antitumor therapy, including as an ideal carrier for drugs/genes, phototherapy, and bioimaging, are systematically summarized. Then, the biosafety of the graphene oxide-based multifunctional nanomaterials is reviewed.

Conclusions

Finally, the conclusions and perspectives on further advancing the graphene oxide-based multifunctional nanomaterials toward potential and versatile development for fundamental researches and nanomedicine are proposed.

Graphic abstract

Two-photon ratiometric fluorescent probe based on NBD-amine functionalized semiconducting polymer nanoparticles for real-time imaging of hydrogen sulfide in living cells and zebrafish

The thiolysis of 7-nitro-1,2,3-benzoxadiazole amine (NBD-A) paves the way for specific sensing of H₂S over biothiols and real-time imaging in living organisms. Rational fabrication of NBD-A-based probe with ratiometric mode and two-photon excitation is highly appealing to achieve high quality bioimaging. In this work, the NBD-A molecules are assembled with poly(9,9-dioctylfluorenyl-2,7-diyl) polymer nanoparticles, defined as NBD@PFO, to construct two-photon ratiometric probes for H₂S detection through the fluorescence resonance energy transfer (FRET). For the construction of NBD@PFO nanohybrids, polymer nanoparticles are employed as the NBD-A molecular vehicle, energy donor and two-photon absorber, while NBD-A is served as the response unit and energy acceptor. Taking advantages of NBD-A and polymer nanoparticles, the obtained NBD@PFO probes exhibit high selectivity, fast response (<5 s), ratiometric detection and two-photon excitation. Our results indicate that NBD@PFO nanohybrids are successfully applied for monitoring of H₂S concentration in living cells and zebrafish, exhibiting great potential of polymer nanoparticles to improve the imaging capability of an organic small molecular probe.

Cyano Derivatives of 7-Aminoquinoline That Are Highly Emissive in Water: Potential for Sensing Applications

6-Cyano-7-aminoquinoline (6CN-7AQ) and 3-cyano-7-aminoquinoline (3CN-7AQ) were synthesized and found to exhibit intense emission with quantum yield as high as 63 % and 85 %, respectively, in water. Conversely, their derivatives 6-cyano-7-azidoquinoline (6CN-7N₃ Q) and 3-cyano-7-azidoquinoline (3CN-7N₃ Q) show virtually no emission, which makes them suitable to be used as recognition agents in azide reactions based on fluorescence recovery. Moreover, conjugation of 6CN-7AQ with a hydrophobic biomembrane-penetration peptide PFVYLI renders a nearly non-emissive 6CN-7AQ-PFVYLI composite, which can be digested by proteinase K, recovering the highly emissive 6CN-7AQ with ∼200-fold enhancement. The result provides an effective early confirmation for RT-qPCR in viral detection.

Dye-sensitized core-shell NaGdF4:Yb,Er@NaGdF4:Yb,Nd upconversion nanoprobe for determination of H2S

The core-shell NaGdF₄:Yb,Er@NaGdF₄:Yb,Nd upconversion nanoparticles (UCNPs) were successfully obtained with the method of co-precipitation, and the water-solubility of UCNPs was improved by the ligand exchange reaction between nitrosyl tetrafluoroborate (NOBF₄) and nanoparticles. The IR-783 dye with negative charge and NOBF₄-UCNPs with positive charge can bind together by electrostatic action to sensitize UCNPs through the energy transfer from IR-783 to UCNPs. However, with the presence of Na₂S (a commonly used H₂S donor), a highly selective reaction between H₂S and IR-783, which destoried the structure of IR-783 and blocked the energy transfer, thus led to the quenching of luminescent intensity. Based on this, a sensing system for determination of H₂S has been constructed successfully. The linear range of H₂S detection by this system is 0.5-15 μM, and the detection limit is 34.17 nM. Furthermore, the dye-sensitized core-shell NaGdF₄:Yb,Er@NaGdF₄:Yb,Nd upconversion nanoprobe was applied to real sample analysis with satisfactory results.

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.

An azido coumarin-quinoline conjugated fluorogenic dye: Utilizing amide-iminol tautomerism for H2S detection in live MCF-7 cells

Detection of H₂S to analyze some diseases in living lives demands fast response, high selectivity and biocompatibility. Here we designed an azide containing coumarin attached with 8-aminoquinoline via amide backbone (ACAQ) fluorophore as the H₂S sensing probe. Excellent response time of 6 min, high sensitivity with the limit of detection (LOD) of 14.6 nM and high selectivity with other possible interferences are revealed for ACAQ after characterized by spectroscopy, ¹H NMR titration and LC-MS measurements. The sensing strategy is explained by amide-iminol tautomerism and azide reduction. In addition, the successful visualization measurement suggests the practicability of the probe ACAQ for H₂S detection in live samples.

Fluorescent detection of S2- based on ZnMOF-74 and CuMOF-74

The detection of S^2- is of great significance because excess S^2- can lead to a variety of serious physiological diseases. Here, two metal-organic frameworks (MOFs), ZnMOF-74 and CuMOF-74, were synthesized by using 2,5-dihydroxy terephthalic acid with strong fluorescence as organic ligand and Zn²⁺ or Cu²⁺ as central coordination ions for S^2- detection. Both as-prepared ZnMOF-74 and CuMOF-74 displayed nanospheres with a diameter of about 100 nm. Under the excitation of 353 nm, the ZnMOF-74 had a characteristic emission peak at 537 nm and the CuMOF-74 had a characteristic emission peak at 528 nm under excitation of 356 nm. The interaction of S^2- and Zn²⁺ weakened the fluorescence of ZnMOF-74 but the interaction of S^2- with Cu²⁺ to form CuS restored the fluorescence of CuMOF-74, so the ZnMOF-74 and CuMOF-74 were exploited as a fluorescent nanosensor for sensing S^2-. The ZnMOF-74 sensor has a good linear range of 19.6 nmol L^-1-90.0 μmol L^-1, and the limit of detection was as low as 6.53 nmol L^-1. The CuMOF-74 sensor has a good linear relationship with II₀ in the S^2- concentration range of 1.50 nmol L^-1-125 μmol L^-1, and the limit of detection was 1.50 nmol L^-1. The proposed ZnMOF-74 and CuMOF-74 sensor could also detect S^2- in actual samples.

A dual-function oligonucleotide-based ratiometric fluorescence sensor for ATP detection

Adenosine triphosphate (ATP) is the main energy currency of life that plays a vital role in supporting physiological activities in living organisms, including humans. Therefore, accurate and sensitive detection of ATP concentration is necessary in biochemical research and clinical diagnosis. Herein, a ratiometric fluorescence aptasensor was developed for ATP detection. A dual-function DNA strand comprising an ATP-binding aptamer (ABA) and berberine-binding aptamer (BBA) was designed and optimized, in which ABA can capture ATP and thioflavin T (ThT), whereas BBA can capture berberine. Interestingly, the fluorescence intensity of both berberine and ThT were enhanced as they were captured by this dual-function DNA strand. In the presence of ATP, the ABA on the 3'-end of the DNA bound specifically to its target, causing ThT release and a significant drop in ThT fluorescence. However, ATP had no significant effect on the interaction between berberine and DNA, remaining the enhanced fluorescence intensity of berberine stable. Based on this interesting phenomenon, a ratiometric fluorescence sensor was constructed that used the enhanced fluorescence intensity of berberine as reference to measure the fluorescence intensity of ThT for ATP detection. This ratiometric fluorescence strategy had excellent selectivity and high sensitivity towards ATP with a detection limit (3σ) as low as 24.8 nM. The feasibility of application of this method in biological samples was evaluated in human serum and urine samples, where it exhibited a good detection performance.

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 highly selective and sensitive fluorescent probe based on the chromone fluorophore for imaging hydrogen sulfide in living cells

A fluorescent probe that was designed based on the 6-amino chromone fluorophore for detecting H₂S can distinguish H₂S from Cys/GSH under acidic conditions.

A highly sensitive ratiometric fluorescent probe for imaging endogenous hydrogen sulfide in cells

A novel fluorescent probe (QL-N3) has high potential to detect the concentration of endogenous hydrogen sulfide in cells.

Modulation of fluorescence sensing properties of coumarin-based fluorescent probe for H2S and its application in cell imaging

A coumarin-based turn on probe, named 3-((E)-3-(1H-indol-3-yl)acryloyl)-2H-chromen-2-one(IAC) was designed and synthesized for the detection of H₂S in aqueous medium. IAC showed no obvious red fluorescence in Tris-HCl(pH = 7.2, 60% DMF), a 28.2-fold fluorescence enhancement was found when 40 equiv. H₂S was added. Other analytes such as anions, metal ions and GSH, Cys, Gly did no significant fluorescence enhancement at 580 nm to IAC. The red fluorescence enhancement mechanism between IAC and H₂S was considered by DFT and ESI-MS. Overall, IAC was successfully applied in cell imaging.

Design and evaluation of an imager for assessing wound inflammatory responses and bioburden in a pig model

Our work details the development and characterization of a portable luminescence imaging device for detecting inflammatory responses and infection in skin wounds. The device includes a CCD camera and close-up lens integrated into a customizable 3D printed imaging chamber to create a portable light-tight imager for luminescence imaging. The chamber has an adjustable light portal that permits ample ambient light for white light imaging. This imager was used to quantify in real time the extent of two-dimensional reactive oxygen species (ROS) activity distribution using a porcine wound infection model. The imager was used to successfully visualize ROS-associated luminescent activities in vitro and in vivo. Using a pig full-thickness cutaneous wound model, we further demonstrate that this portable imager can detect the change of ROS activities and their relationship with vasculature in the wound environment. Finally, by analyzing ROS intensity and distribution, an imaging method was developed to distinguish infected from uninfected wounds. We discovered a distinct ROS pattern between bacteria-infected and control wounds corresponding to the microvasculature. The results presented demonstrate that this portable luminescence imager is capable of imaging ROS activities in cutaneous wounds in a large animal model, indicating suitability for future clinical applications.

Fast response near-infrared fluorescent probe for hydrogen sulfide in natural waters

Rapid and sensitive detection of hydrogen sulfide (H₂S) is of great importance for the environmental monitoring. Near-infrared fluorescent probes are recently developed for the sensitive H₂S detection thanks to their low background interference, while often hampered by relatively long response time (around 30 min). In this work, we reported a fast response (within 5 min), highly sensitive near-infrared (NIR) fluorescent probe (DCM-OCN) for H₂S. The rapid nucleophilic reaction between cyanate moiety and H₂S endowed fast response of the NIR probe. The influence of experimental parameters (including CTAB concentration, reaction time, pH value etc.), interference study, and possible mechanism were investigated in detail. The fluorescence increment was linear with H₂S concentration in 1-10 μM with a detection limit of 0.28 μM (3σ). The probe was successfully applied to environmental water samples including river water, tap water, lake water, mineral water and artificial wastewater.

An instantaneous fluorescent probe for detecting hydrogen sulfide in biological systems

An instantaneous (within seconds) fluorescent probe for detecting H₂S was developed and successfully used for H₂S imaging in living cells and zebrafish.

A reversible and turn-on type fluorescence behaviour of hydrogen sulfide via a redox cycle between selenoxide and selenide

Upon treatment with H₂S in MeCN–PBS, the fluorescence dormant selenoxides of dibenzobarrelene- and benzobarrelene-based 1-seleno-1,3-butadiene derivatives are rapidly converted to strongly fluorescent selenides.