Zincke's Salt-Substituted Tetraphenylethylenes for Fluorometric Turn-On Detection of Glutathione and Fluorescence Imaging of Cancer Cells

Responsive Organic Fluorescent Aggregates Based on Ion-π Interactions Away from Fluorescent Conjugated Groups

Responsive organic luminescent aggregates have a wide range of application fields, but currently there is still a lack of reasonable molecular design strategies. Introducing ion-π interactions into molecules can effectively alter their luminescent properties. However, current research typically focuses on ion localization at luminescent conjugated groups with the strong interaction forces. In this work, we introduce the flexible alkoxy chain spacers between fluorescent conjugated groups and ion-π interaction sites, and then adjust the fluorescence performance of the molecule by changing the strength of ion-π interactions. Bromine ion-based molecules with strong ion-π interactions exhibit high and stable fluorescence quantum yields in crystals and amorphous powders under the external stimuli. Hexafluorophosphate ion-based molecules with weak ion-π interactions have the high fluorescence quantum yield in crystals and very low fluorescence quantum yield in amorphous powders, showing variable fluorescence intensities under external stimuli. This demonstrates a new class of responsive organic luminescent solid-state materials.

Glutathione-responsive Aggregation-induced Emission Photosensitizers for Enhanced Photodynamic Therapy of Lung Cancer

Lung cancer, a highly prevalent and lethal form of cancer, is often associated with oxidative stress. Photodynamic therapy (PDT) has emerged as a promising alternative therapeutic tool in cancer treatments, but its efficacy is closely correlated to the photosensitizers generating reactive oxygen species (ROS) and the antioxidant capacity of tumor cells. In particular, glutathione (GSH) can reduce the ROS and thus compromise PDT efficacy. In this study, a GSH-responsive near-infrared photosensitizer (TBPPN) based on aggregation-induced emission for real-time monitoring of GSH levels and enhanced PDT for lung cancer treatment is developed. The strategic design of TBPPN, consisting of a donor-acceptor structure and incorporation of dinitrobenzene, enables dual functionality by not only the fluorescence being activated by GSH but also depleting GSH to enhance the cytotoxic effect of PDT. TBPPN demonstrates synergistic PDT efficacy in vitro against A549 lung cancer cells by specifically targeting different cellular compartments and depleting intracellular GSH. In vivo studies further confirm that TBPPN can effectively inhibit tumor growth in a mouse model with lung cancer, highlighting its potential as an integrated agent for the diagnosis and treatment of lung cancer. This approach enhances the effectiveness of PDT for lung cancer and deserves further exploration of its potential for clinical application.

Identification of Microorganism in Infected Wounds by Positively Charged Selective Sensor Array and Deep Learning Algorithm

Microorganism are ubiquitous and intimately connected with human health and disease management. The accurate and fast identification of pathogenic microorganisms is especially important for diagnosing infections. Herein, three tetraphenylethylene derivatives (S-TDs: TBN, TPN, and TPI) featuring different cationic groups, charge numbers, emission wavelengths, and hydrophobicities were successfully synthesized. Benefiting from distinct cell wall binding properties, S-TDs were collectively utilized to create a sensor array capable of imaging various microorganisms through their characteristic fluorescent signatures. Furthermore, the interaction mechanism between S-TDs and different microorganisms was explored by calculating the binding energy between S-TDs and cell membrane/wall constituents, including phospholipid bilayer and peptidoglycan. Using a combination of the fluorescence sensor array and a deep learning model of residual network (ResNet), readily differentiation of Gram-negative bacteria (G-), Gram-positive bacteria (G+), fungi, and their mixtures was achieved. Specifically, by extensive training of two ResNet models with large quantities of images data from 14 kinds of microorganism stained with S-TDs, identification of microorganism was achieved at high-level accuracy: over 92.8% for both Gram species and antibiotic-resistant species, with 90.35% accuracy for the detection of mixed microorganism in infected wound. This novel method provides a rapid and accurate method for microbial classification, potentially aiding in the diagnosis and treatment of infectious diseases.

A tetraphenylethene-based Schiff base AIEgen with a large Stokes shift as probe for highly sensitive and selective detection of aqueous Cu2+ ions and its application in cell imaging

In this work, an AIE-active tetraphenylethene-based Schiff base fluorescent probe 3 with a large Stokes shift (247 nm) was designed and synthesized. It was found that the aggregated probe 3 exhibited very high selectivity and anti-interference ability for Cu²⁺ in PBS buffer (70% f_w) through a fluorescence "turn-off" strategy. Job's plot and NMR analysis indicated the two phenolic hydroxyl groups of the benzene ring and the N atom (-CH=N-) on probe 3 interacted with Cu²⁺ ions in a 1:1 stoichiometric ratio. A comprehensive analysis of the Stern-Volmer and binding constant indicated a rather strong interaction between probe 3 and Cu²⁺ ions. Probe 3 illustrated excellent sensitivity toward Cu²⁺ under ppb level (4.5 nM) and achieved more than 95% recovery in river, lake and tap water toward estimation of Cu²⁺ ions in the analytical applications. Moreover, probe 3 was able to realize bioimaging of HepG2 cells and be quenched by intracellular Cu²⁺ ions, making it promising as a sensitive Cu²⁺ sensor for organisms.

Fluorescent-based nanosensors for selective detection of a wide range of biological macromolecules: A comprehensive review

Thanks to their unique attributes, such as good sensitivity, selectivity, high surface-to-volume ratio, and versatile optical and electronic properties, fluorescent-based bioprobes have been used to create highly sensitive nanobiosensors to detect various biological and chemical agents. These sensors are superior to other analytical instrumentation techniques like gas chromatography, high-performance liquid chromatography, and capillary electrophoresis for being biodegradable, eco-friendly, and more economical, operational, and cost-effective. Moreover, several reports have also highlighted their application in the early detection of biomarkers associated with drug-induced organ damage such as liver, kidney, or lungs. In the present work, we comprehensively overviewed the electrochemical sensors that employ nanomaterials (nanoparticles/colloids or quantum dots, carbon dots, or nanoscaled metal-organic frameworks, etc.) to detect a variety of biological macromolecules based on fluorescent emission spectra. In addition, the most important mechanisms and methods to sense amino acids, protein, peptides, enzymes, carbohydrates, neurotransmitters, nucleic acids, vitamins, ions, metals, and electrolytes, blood gases, drugs (i.e., anti-inflammatory agents and antibiotics), toxins, alkaloids, antioxidants, cancer biomarkers, urinary metabolites (i.e., urea, uric acid, and creatinine), and pathogenic microorganisms were outlined and compared in terms of their selectivity and sensitivity. Altogether, the small dimensions and capability of these nanosensors for sensitive, label-free, real-time sensing of chemical, biological, and pharmaceutical agents could be used in array-based screening and in-vitro or in-vivo diagnostics. Although fluorescent nanoprobes are widely applied in determining biological macromolecules, unfortunately, they present many challenges and limitations. Efforts must be made to minimize such limitations in utilizing such nanobiosensors with an emphasis on their commercial developments. We believe that the current review can foster the wider incorporation of nanomedicine and will be of particular interest to researchers working on fluorescence technology, material chemistry, coordination polymers, and related research areas.

AIE materials for cancer cell detection, bioimaging and theranostics

AIE materials exhibit weakly emissive or non-emissive properties in dilute solutions while emit powerful fluorescence in the aggregated/solid state. Recently, AIE based materials have gained immense attention due to their multifunctional role in cancer cell detection, bioimaging and cancer theranostics. In this present book chapter, we will highlight recent advancements of AIE materials for different cancer theranostics applications.

Highly uniform self-assembled monolayers of silver nanospheres for the sensitive and quantitative detection of glutathione by SERS

The homeostasis and imbalance of glutathione (GSH), an important antioxidant in organisms, are one of the key signals that reflect the health of organisms. In this paper, a novel SERS sensing platform based on Ag film@Si that self-assembled using silver nanospheres was proposed, which was used for the highly sensitive and selective detection of GSH. With the aid of an oil/water/oil three-phase system, the nano-silver film was self-assembled and finally deposited on silicon wafers. The heterobifunctional crosslinking agent N-succinimidyl-3-(2-pyridyldithio)propionate (SPDP), which contains pyridine rings and disulfide bonds, was involved in the exchange reaction between the sulfhydryl groups and disulfide bonds. With the addition of GSH, the breakage of disulfide bonds was promoted, thereby enhancing the SERS signal of SPDP. GSH can be detected sensitively by detecting the changes in the SPDP signal. The detection limit of GSH is 10 nM, and the method is still highly stable when the external environment is serum or other more complex environments.

Azulene-Substituted Donor-Acceptor Polymethines and 1,6'-Bi-, 1,6';3,6''-Ter-, and Quinqueazulenes via Zincke Salts: Synthesis, and Structural, Optical, and Electrochemical Properties

Azulene-substituted donor-acceptor polymethines, bi-, ter-, and quinqueazulenes composed of the 1,6'-biazulene unit have been successfully prepared from corresponding Zincke salts. The synthesis of polymethines through the reaction of Zincke salts with several amines, followed by a Knoevenagel reaction with malononitrile, was accomplished in moderate to high yields (40-92 %). Meanwhile, the reaction of Zincke salts with secondary amines and the subsequent sequential condensation-cyclization with cyclopentadienide ions, so-called Ziegler-Hafner method, produced the corresponding 1,6'-biazulenes, 1,6';3,6''-terazulenes, and quinqueazulene, respectively. The structural, optical, and electrochemical properties of the azulene-substituted donor-acceptor polymethines, bi-, ter-, and quinqueazulenes were revealed by single-crystal X-ray structure analysis, UV/vis spectroscopy, voltammetry analysis, spectroelectrochemistry, and theoretical calculations. These results suggested that the substituents on the azulene ring and their substitution positions directly affect their reactivities, optical and electrochemical properties.

Recent advances of AIE light-up probes for photodynamic therapy

As a new non-invasive treatment method, photodynamic therapy (PDT) has attracted great attention in biomedical applications. The advantages of possessing fluorescence for photosensitizers have made it possible to combine imaging and diagnosis together with PDT. The unique features of aggregation-induced emission (AIE) fluorogens provide new opportunities for facile design of light-up probes with high signal-to-noise ratios and improved theranostic accuracy and efficacy for image-guided PDT. In this review, we summarize the recent advances of AIE light-up probes for PDT. The strategies and principles to design AIE photosensitizers and light-up probes are firstly introduced. The application of AIE light-up probes in photodynamic antitumor and antibacterial applications is further elaborated in detail, from binding/targeting-mediated, reaction-mediated, and external stimuli-mediated light-up aspects. The challenges and future perspectives of AIE light-up probes in the PDT field are also presented with the hope to encourage more promising developments of AIE materials for phototheranostic applications and translational research.

A fluorescence turn-on probe for hydrogen sulfide and biothiols based on PET & TICT and its imaging in HeLa cells

In this paper, a photoinduced electron transfer (PET)& twisted intramolecular charge transfer (TICT)-based fluorescent probe (1) for detecting biothiols (GSH/Cys/Hcy) and hydrogen sulfide with fluorescence turn on was developed. The probe could recognize hydrogen sulfide over primary ions and selectively detect GSH/Cys/Hcy over other amino acids with fluorescence turn-on (an ESIPT process). H₂S can be distinguished from GSH/Cys/Hcy with wavelength shift by UV-Vis spectra. In addition, detection limits for H₂S/GSH/Cys/Hcy of probe 1 were 1.42 μM (0-100 μM), 0.13 μM (0-40 μM), 0.27 (0-30 μM), 0.22 μM (0-40 μM), respectively. The proposed thiolysis of the 2,4-dinitrochlorophenyl ether reaction in identification process was verified by the characteristic peak in ¹H NMR and HRMS spectra. Finally, the biological imaging experiments and low cytotoxicity investigations in HeLa cells demonstrated that probe 1 could provide a promising method for the determination of H₂S and biothiols in aqueous solution and living cells.

A novel supramolecule-based fluorescence turn-on and ratiometric sensor for highly selective detection of glutathione over cystein and homocystein

A cyclodextrin-based fluorescence light-up and ratiometric sensor is reported for highly selective and sensitive recognition of glutathione over cystein and homocystein. The sensing scheme developed builds up on a supramolecular assembly formed between a molecular rotor dye (ThT) and a polyanionic supramolecular host (sulfated-β-cyclodextrin, SCD). The detection scheme is accomplished as follows: firstly, the bivalent Cu²⁺ quenches the emission from ThT-SCD assembly by causing the dissociation of ThT molecules from SCD surface. Secondly, when GSH is added to the copper-quenched system, owing to specific interaction between Cu²⁺ and GSH, Cu²⁺ is removed from the SCD which again allows the formation of ThT-SCD assembly. Indeed, this scheme of disassembly and reassembly successively caused by Cu²⁺ and GSH in the aqueous solution empowers our sensor framework to work as a good ratiometric sensor for the detection of GSH. The sensor scheme shows a linear response in the range 0-250 μM with a LOD of 2.4 ± 0.2 μM in aqueous solution and 13.6 ± 0.5 μM in diluted human serum sample. The sensor system is excited at 410 nm and the emission signal is plotted as a ratio of intensity at 545 nm (aggregate band) and 490 nm (monomer band). This ratiometric sensor system is highly selective to glutathione over cystein, homocystein, and other amino acids. Additionally, response of the sensor system towards GSH in complex biological media of serum samples demonstrates its potential for practical utility. Graphical abstract.

Aggregation-Induced Emission Luminogens for Mitochondria-Targeted Cancer Therapy

The importance of mitochondria in tumorigenesis makes these organelles an ideal target for cancer therapy. In recent years, luminogens with the aggregation-induced emission (AIE) effect have been developed for mitochondrial targeting and cancer treatment. The induction of mitochondrial dysfunction can be an effective pathway of chemotherapy, photodynamic therapy, and combination therapy against cancer. This review focuses on recent progress in the field of AIE luminogens (AIEgens) for cancer theranostics based on mitochondrial targeting and dysfunction. AIEgens for cancer treatment, including chemotherapy, photodynamic therapy, and combination therapy, are summarized herein. Molecular design efforts toward mitochondrial targeting and mitochondria-damaging mechanisms are also discussed. Finally, we discuss the challenges and future directions of development for AIEgens in mitochondria-targeted cancer treatment.

Recent Progress of Glutathione (GSH) Specific Fluorescent Probes: Molecular Design, Photophysical Property, Recognition Mechanism and Bioimaging

The selective detection of glutathione (GSH) in vitro and in vivo has attracted great attentions, credited to its important role in life activities and association with a series of diseases. Among all kinds of analytical techniques, the fluorescent probe for GSH detection become prevalent recently because of its ease of operation, high temporal-spatial resolution, visualization and noninvasiveness, etc. The special structural features of GSH, such as the nucleophilicity of sulfhydryl group, the concerted reaction ability of amino group, the negative charged nature, the latent hydrogen bonding ability along with its flexible molecular chain, are all potent factors to be employed to design the specific fluorescent probe for GSH and discriminate it from other bio-species including its analogues cysteine (Cys) and homocysteine (Hcy). This paper reviewed the studies in the last 3 years and was organized based on the reaction mechanism of each probe. According to the reactivity of GSH, various recognition mechanisms including Michael addition, nucleophilic aromatic substitution, ordinary nucleophilic substitution, multi-site reaction, and other unique reactions have been utilized to construct the GSH specific fluorescent probes, and the molecular design strategy, photophysical property, recognition mechanism, and bioimaging application of each reported probe were all discussed here systematically. Great progress has been made in this area, and we believe the analyses and summarization of these excellent studies would provide valuable message and inspiration to researchers to advance the research toward clinic applications.

Multi-Stimuli Responsive FRET Processes of Bifluorophoric AIEgens in an Amphiphilic Copolymer and Its Application to Cyanide Detection in Aqueous Media

A novel amphiphilic aggregation-induced emission (AIE) copolymer, that is, poly(NIPAM-co-TPE-SP), consisting of N-isopropylacrylamide (NIPAM) as a hydrophilic unit and a tetraphenylethylene-spiropyran monomer (TPE-SP) as a bifluorophoric unit is reported. Upon UV exposure, the close form of non-emissive spiropyran (SP) in poly(NIPAM-co-TPE-SP) can be photo-switched to the open form of emissive merocyanine (MC) in poly(NIPAM-co-TPE-MC) in an aqueous solution, leading to ratiometric fluorescence of AIEgens between green TPE and red MC emissions at 517 and 627 nm, respectively, via Förster resonance energy transfer (FRET). Distinct FRET processes of poly(NIPAM-co-TPE-MC) can be observed under various UV and visible light irradiations, acid-base conditions, thermal treatments, and cyanide ion interactions, which are also confirmed by theoretical studies. The subtle perturbations of environmental factors, such as UV exposure, pH value, temperature, and cyanide ion, can be detected in aqueous media by distinct ratiometric fluorescence changes of the FRET behavior in the amphiphilic poly(NIPAM-co-TPE-MC). Moreover, the first FRET sensor polymer poly(NIPAM-co-TPE-MC) based on dual AIEgens of TPE and MC units is developed to show a very high selectivity and sensitivity with a low detection limit (LOD = 0.26 μM) toward the cyanide ion in water, which only contain an approximately 1% molar ratio of the bifluorophoric content and can be utilized in cellular bioimaging applications for cyanide detections.

Enhancement of the Aggregation-Induced Emission by Hydrogen Bond for Visualizing Hypochlorous Acid in an Inflammation Model and a Hepatocellular Carcinoma Model

As an important reactive oxygen species, hypochlorous acid (HClO) is produced in various physiological processes. The abnormal rise of the HClO level is associated with a large number of inflammatory diseases. In this work, we develop a simple, aqueous-soluble aggregration-induced emission (AIE) probe for sensing HClO with significant aggregation-induced fluorescence (>1000 times). Two probes, CH₃O-TPE-Py⁺-N⁺ (COTN) and OH-TPE-Py⁺-N⁺ (HOTN) (TPE, tetraphenylethylene), are synthesized for sensing HClO by the cleavage of the Py⁺-N⁺ group; the reaction products are CH₃O-TPE-CHO (COT) and OH-TPE-CHO (HOT), respectively. The hydrophobicity of the probes is changed with the increased aggregation-induced emission. During the process, HOTN shows significantly better response than COTN. The slightly different chemical structures of COTN and HOTN result in a significant response to HClO. The theoretical calculation data support the theory that the hydrogen bond contributes to the excellent sensitivity for HClO. On the basis of the good response to HClO in vitro, HOTN is used to image inflammation and hepatocellular carcinoma in vivo because these diseases always produce high HClO levels.

Controlled assembly of AIEgens based on a super-quadruplex scaffold for detection of plasma membrane proteins

Quantification of plasma membrane proteins (PMPs) is crucial for understanding the fundamentals of cellular signaling systems and their related diseases. In this work, a super-quadruplex scaffold was designed to regulate assembly of oligonucleotide-grafted AIEgens for detection of PMPs. The nonfluorescence oligonucleotide-grafted AIEgen (Oligo-AIEgen) was firstly synthesized by attaching the AIEgen to 3'-terminus of the oligonucleotide through click chemistry. Meanwhile, the tetramolecular hairpin-conjugated super-quadruplex (THP-G4) as cleavage element and signal enhancement scaffold composited of three elements: a substrate sequence of DNAzyme in the loop region, partial hybridization region in the stem, and six guanine nucleotides to form G-quadruplex. Once the DNAzyme was anchored on the specific PMPs through aptamer-protein recognition, the substrate sequence on the loop of THP-G4 was cleaved by DNAzyme with the aid of cofactor Mn^II, resulting in the conformation switch of THP-G4 to the activated G-quadruplex scaffold. The latter could assemble Oligo-AIEgens to generate aggregation-induced emission (AIE) enhancement, resulting in a simple and sensitive strategy for detection of membrane proteins. Moreover, the DNAzyme continuously cut the next THP-G4 to achieve recycling amplification. Under the optimized conditions, this AIE-based strategy exhibited good linear relationship with the logarithm of MUC1 concentration from 0.01 to 10 μg mL^-1 with the limit of detection down to 4.3 ng mL^-1. The G4-assembled AIEgens provides a universal platform for detecting various biomolecules and a proof-of concept for AIE biosensing.

Tetrathienylethene-based Positional Isomers with Aggregation-induced Emission Enabling Super Red-shifted Reversible Mechanochromism and Naked-eye Sensing of Hydrazine Vapor

AIE-active positional isomers, TTE-o-PhCHO, TTE-m-PhCHO and TTE-p-PhCHO, tetrathienylethene (TTE) derivates with peripherally attached ortho-/meta-/para-formyl phenyl groups, were designed and synthesized. The formyl substitution position can effectively modulate their photophysical properties, mechanochromism and fluorescent response to hydrazine. TTE-o-PhCHO and TTE-m-PhCHO exhibit remarkable AIE characteristics, and TTE-p-PhCHO possesses aggregation-induced emission enhancement performance. They all exhibit high contrast mechanochromism, and TTE-m-PhCHO shows larger red-shift (164 nm) than TTE-o-PhCHO (104 nm) and TTE-p-PhCHO (125 nm) due to the more twisted molecular conformation and much looser molecular packing. Moreover, TTE-o-PhCHO with a higher contrast color change can be used as ink-free rewritable paper. In addition, TTE-p-PhCHO, as a turn-on fluorescent probe, can selectively detect hydrazine with significant color changes that are visible by the naked eye . Therefore, the position dependence of groups would be an effective method to modulate the molecular arrangement, as well as develop AIE compounds for mechano-stimuli responsive materials, ink-free rewritable papers and chemosensors.

Lysosome-Targeting Red-Emitting Aggregation-Induced Emission Probe with Large Stokes Shift for Light-Up in Situ Visualization of β-N-Acetylhexosaminidase

Lysosomal β-N-acetylhexosaminidase (Hex) has been reported to possess unique physiological performances. Detection and visualization of Hex in lysosome will be favorable to reveal the basis of its functions. However, Hex-specific fluorescent probes are rarely reported. In this study, we reported the first lysosome-targeting Hex-lighting-up aggregation-induced emission (AIE)-active fluorescent probe (GlcNAc-TPE) with remarkably large Stokes shift and high sensitivity and selectivity. GlcNAc-TPE can selectively locate in lysosome and visualize endogenous Hex in live HCT116 cells and in live mice with high stability and good biocompatibility, providing a useful AIE probe for real-time visualization of Hex in live samples.

Precise Synthesis of GSH-Specific Fluorescent Probe for Hepatotoxicity Assessment Guided by Theoretical Calculation

Drug-induced hepatotoxicity is the main cause of acute liver injury, and its early diagnosis is indispensable in pharmacological and pathological studies. As a hepatotoxicity indicator, the GSH distribution in the liver could reflect the damage degree in situ. In this work, we have provided a theoretical design strategy to determine the generation of photo-induced electron transfer mechanism and achieve high selectivity for the target. After that, we precisely synthesized a novel near-infrared fluorescent probe BSR1 to specifically monitor endogenous GSH and hepatotoxicity in biosystem with a moderate fluorescent quantum yield (Φ = 0.394) and low detection limit (83 nM) under this strategy. Moreover, this mapping method for imaging GSH depletion in vivo to assay hepatotoxicity may provide a powerful molecular tool for early diagnosis of some diseases and contribute to assay hepatotoxicity for the development of new drugs. Importantly, this theoretical calculation-guided design strategy may provide an effective way for the precise synthesis of the target-specific fluorescent probe and change this research area from "trial-and-error" to concrete molecular engineering.

Aggregation-induced-emission (AIE) directed assembly of a novel responsive nanoprobe for dual targets sensing

The employment of aggregation induced emission (AIE) species for detecting analytes has become ubiquitous in many applications ranging from environmental monitoring to novel chemical sensing processes. Herein, a new organic building block (4,4',4″,4″'-(ethene-1,1,2,2-trayltetrakis (benzene-4,1-diyl))tetrakis(1-methylpyridin-1-ium) boric acid (TPE-B)) has been synthesized and such chromophore exhibits very weak emission in aqueous solution. The molecule-surfactant interaction can lead to distinguished yellow emissions and the incorporation of sodium dodecyl sulfonate (SDS) will generate morphological changes from irregular organic clusters to aggregated nanoparticles with the size of 45 nm. A six-fold intensity enhancement has been observed and the electrostatic forces are believed to act as the primary role for the selective response to SDS. Based on the in situ established TPE-B-SDS framework, a switched-off effect has been observed in the presence of ClO^- and this signal change will allow us to accurately determine the concentration of such reactive oxygen species (ClO^-). The limits of detection for SDS and ClO^- are calculated to be 54.2 nM and 14.2 nM, respectively. These excellent optical properties have been extended into practical range and the results for the detection of SDS and ClO^- in tap water samples are satisfactory. It is anticipated that the responsive probe will provide deeper insights into multi-targets sensing in extensive systems.

Tetraphenylethene decorated with disulfide-functionalized hyperbranched poly(amido amine)s as metal/organic solvent-free turn-on AIE probes for biothiol determination

Novel hyperbranched poly(amido amine)s AIE probes were developed for organic solvent-free biothiol sensing.

A red mitochondria-targeted AIEgen for visualizing H2S in living cells and tumours

A red mitochondria-targeted AIEgen with greater conjugate and more positive charges for visualizing H₂S in cells and tumours.

Glutathione-selective “off–on” fluorescence response by a probe-displaced modified ligand for its detection in biological domains

The glutathione-induced oxidation of benzylic-alcohol into the formyl moiety in the ligand displaced from the Cu(ii)-complex exhibits in vitro and in vivo “off–on” fluorescence responses.

A two-separated-emission fluorescent probe for simultaneous discrimination of Cys/Hcy and GSH upon excitation of two different wavelengths

It is challenging to simultaneously discriminate two or three biothiols from each other due to their structural similarities as well as reactions sites. The development of multiple-signal fluorescent probes would be a promising way to overcome this issue. Herein, a two-separated-emission fluorescent probe for biothiols was developed based on the combination of nitrobenzofurazan (NBD) and phenanthroimidazole fluorophores linked by a facile ether bond. In the presence of Cys and Hcy, the probe in DMF-H₂O demonstrates two separate fluorescence emissions at 480 and 550 nm upon excitation of two independent wavelengths. However, addition of GSH to the probe only leads to blue fluorescence at 480 nm. This difference can be reasonably ascribed to the fact that the NBD-GSH intermediate, unlike NBD-Cys/Hcy, cannot undergo an intramolecular cyclization-rearrangement reaction. The probe exhibits a rapid response with low limits of detection (14.7 nM for Cys, 14.4 nM for Hcy, and 13.4 nM for GSH) with large concentration ranges of 0-100 μM for Cys/Hcy and 0-200 μM for GSH. Furthermore, the probe is successfully applied to simultaneously distinguish endogenous Cys, Hcy, and GSH in living HeLa cells and zebrafish models.