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Emerging studies demonstrates that mitochondrial G-quadruplex (G4) may be a prospective diagnostic and therapeutic target for cancer. Fluorescent probes targeting mitochondrial G4 are crucial for in-depth research on G4 function and mechanism and developing new diagnostic techniques. Here, we report a benzothiazole derivative named ThT-E, which can be prepared with high yield through only one step of reaction. ThT-E exhibits superior detection sensitivity compared to existing probes, and also demonstrates reliable performance for in situ characterization of mitochondrial G4 in living cells. Interestingly, ThT-E has been used to differentiate tumor cells from normal cells by quantifying the formation of mitochondrial G4s, implicating that ThT-E may have wide applications in tumor diagnosis. • A benzothiazole derivative for monitoring mitochondrial G-quadruplexes. • More pronounced fluorescence enhancement in tumor cells than normal cells. • More G-quadruplex formation in tumor mitochondria. • Mitochondrial G-quadruplex as a potential cancer biomarker. • New probe tool for tumor diagnosis. [ABSTRACT FROM AUTHOR]

Mitophagy is a critical cellular self-protective mechanism involving the degradation and recycling of damaged or excessive mitochondria, which has been implicated in various diseases. In our study, we designed and synthesized two phenothiazine-based fluorescent probes, DPTZ and CMDP , specifically targeting mitochondria and lysosomes, respectively, to investigate mitophagy. H 2 S, a cell-protective agent, was chosen as the target molecule for both probes. Our findings demonstrate the selective localization of DPTZ to mitochondria and CMDP to lysosomes. Both probes exhibited rapid, selective, and highly sensitive recognition of H 2 S, enabling imaging of exogenous and endogenous H 2 S. By employing split-targeting and simultaneous detection, we were able to monitor changes in H 2 S levels in mitochondria and lysosomes, providing dynamic and visual imaging of the mitophagy processes. Upregulation of mitochondrial and lysosomal H 2 S was observed during mitochondrial autophagy. This work introduces valuable research methods and tools for investigating mitophagy, thereby enhancing our understanding of the molecular mechanisms underlying this process. [Display omitted] • Phenothiazine-based probes DPTZ and CMDP detect hydrogen sulfide. • DPTZ and CMDP target mitochondria and lysosomes for imaging in A549 cells. • Split-targeting and detection strategy reveals hydrogen sulfide fluctuations in autophagy. [ABSTRACT FROM AUTHOR]

The investigation of cell membrane polarity is critical to determining cell physiological states and related disease for diagnosis and treatment. Herein, a ratiometric NIR cell membrane-targeted fluorescent probe, Cy-C 12 -MpN , was designed and synthesized to assess cell membrane polarity, which has an amphiphilic structure consisting of a dodecyl unit and a quaternary ammonium unit. It exhibited changes in emission wavelength and fluorescence intensity with the changes in polarity of the solution. It can use the ratio signal of the two peaks to report the polarity difference in its environment. The self-tuning of the probe internal system ensures the reliability of the test results and can be a semi-quantitative detection method. Indeed, in vitro polarity test, the ratio signal reported by Cy-C 12 -MpN had an optimal linear range with respect to polarity. Cell imaging illustrated the excellent cell membrane-targeted ability of Cy-C 12 -MpN , as it can rapidly target the cell membrane within 30 s and still anchor at it well after 1 hr. Moreover, Cy-C 12 -MpN showed that cell membrane polarity decreases after cells become cancerous, and observed the changes in cell membrane polarity caused by homeostatic membrane response stimulated by polyunsaturated fatty acids firstly. Imaging in vivo demonstrated the ability of Cy-C 12 -MpN to distinguish between tumor cells and normal cells, and further demonstrated that tumor cells have lower cell membrane polarity. In summary, the accuracy of the ratio detection of the probe Cy-C 12 -MpN and its excellent cell membrane targeting ability reveal reliable results that can provide very useful insights for cancer research. [Display omitted] • A novel NIR fluorescent probe for ratiometric detection of cell membrane polarity. • The degree of electron-hole transfer of the probe is calculated by Multiwfn to evaluate its polarity sensitivity. • The changes of cell membrane polarity in cell membrane homeostasis response stimulated by DHA were revealed. [ABSTRACT FROM AUTHOR]

Stress granules (SGs) are a fascinating type of membrane-less organelle that form through liquid-liquid phase separation in eukaryotic cells. Our previous investigations have been instrumental in the development of the first small-molecule fluorescent probe, named TASG , which can selectively identify SGs. However, the practical utility of TASG for monitoring SG dynamics in live cells has been hindered by the difficulty in visualizing small nascent SGs. To overcome this obstacle, the present study systematically modified the structure of TASG , with the aim of discovering fluorescent chemical probes that exhibit superior performance. Among the evaluated candidates, TASG-8 exhibited the most promising ability to image SGs. Importantly, TASG-8 possessed a critical advantage over TASG , in that it could effectively label small nascent SGs. The structure-activity relationship of the candidates was analyzed. Additionally, the underlying mechanism responsible for this enhancement was extensively explored. Collectively, our research presents a rational strategy for the development of innovative fluorescent probes that selectively target SGs, and introduces a powerful new tool, TASG-8 , which has the potential to facilitate more comprehensive and efficient investigations into the functions of SGs in cells. • The structure-activity relationship of benzothiazoles that target SGs is clarified. • TASG-8 is the first fluorescent probe capable of visualizing small nascent SGs. • Our study presents a novel concept for developing probes that are specific to SGs. [ABSTRACT FROM AUTHOR]

The misfolding and aggregation of specific proteins induced by endogenous oxidation are closely related to some incurable diseases including cancers, diabetes and neurodegenerative diseases. Reactive oxygen species (ROS), as a common oxidizing substance in vivo would induce the oxidation of endogenous biomacromolecules like proteins. However, it remains a challenge to detect protein aggregation induced by specific ROS. Herein, we demonstrate that the developed probe (P2) with a dual function that can simultaneously detect hydrogen peroxide (H 2 O 2) levels and protein aggregates formed by oxidative stress. In this probe, the boronic acid pinacol ester group was conjugated to fluorescent molecular rotor 4-hydroxybenzylidene-imidazolinone (HBI) and served as the H 2 O 2 detection group. Experimental results show that the fluorescence of P2 can be activated by H 2 O 2 and exhibited a positive correlation with the degree of protein aggregation. Moreover, combined with AggTag method P2 was successfully applied to dual-channel imaging of protein aggregation that is stressed by H 2 O 2 in cellular. In general, this work not only provides a potential method to study protein aggregation that associates with oxidation in live cells but also can be generally applied to study other biological processes. • A dual-functional probe activated by hydrogen peroxide (H 2 O 2) and viscosity was designed and synthesized. • The probe responds to H 2 O 2 with high selectivity. • The probe exhibits a cascade response to H 2 O 2 and protein aggregation. • Revealing the process of protein aggregation under H 2 O 2 stress in live cells. [ABSTRACT FROM AUTHOR]

• A dicyanoisophorone-based fluorescent probe was developed for sensing H 2 S with a large Stokes shift (155 nm). • The probe showed faster time response and high sensitivity for H 2 S. • The probe can be used to detect exdogenous and endogenous H 2 S in living HeLa cells. Due to the importance of hydrogen sulfide (H 2 S) in physiology and pathology, the development of fluorescence probes for the detection of H 2 S has attracted extensive attention of researchers. We developed a H 2 S fluorescence probe (DCN-S) based on dicyanoisopentanone using dithioether and ester groups as the reaction sites. Under the nucleophilic substitution of H 2 S, disulfide bond of DCN-S was broken. Then the probe changed into dicyanoisophorone derivative and emitted an orange fluorescence band from 530 nm to 700 nm (centred 580 nm). Upon response for H 2 S, DCN-S exhibited high sensitivity (88 nM detection limit) and large stokes shift (155 nm). Importantly, the probe also was successfully used for endogenous and exogenous imaging of living cells. [ABSTRACT FROM AUTHOR]

Hypochlorous acid (HOCl) is a crucial reactive oxygen species in biological systems, and its abnormal metabolism is associated with various diseases. Therefore, it is essential to accurately detect HOCl to understand its biological function and develop related therapeutic strategies for diseases. In this work, we developed a novel fluorescence probe, BCy-S , based on the twisted intramolecular charge transfer (TICT) mechanism for rapid and sensitive detection of HOCl in an aqueous solution. The probe exhibited a significant turn-on fluorescence response to HOCl, with high selectivity, rapid kinetics (less than 40 s), large Stokes shift (about 170 nm), and low detection limit (35.2 nM), based on the specific oxidation reaction of HOCl with sulfur atoms. Additionally, the outcomes of the bioimaging experiment showed that BCy-S was capable of real-time fluorescence visualization of HOCl in living HeLa cells and zebrafish. The development of BCy-S presents a new tool for investigating the physiological function of HOCl and its pathological role in diseases. [Display omitted] • A new TICT-based HOCl fluorescent probe has been designed and developed. • The probe exhibits an excellent sensitivity, large Stokes Shift and low detection limit to HOCl. • The probe could be applied for real-time fluorescence imaging of HOCl in live HeLa cells and zebrafish. [ABSTRACT FROM AUTHOR]

The abnormal changes of intracellular potassium ion (K+) concentration are usually associated with various diseases, therefore, real-time monitoring of intracellular K+ dynamic balance is crucial for disease research. Herein, we present a design strategy based on conjugated polymers (CPs) as potassium ion fluorescence probes. Six novel CP-based K+ sensors (P1 , P2 , P3 , PP1 , PP2 and PP3) were synthesized. These probes have different conjugated length backbones composing of stilbenzene, fluorene, thiophene, and/or benzothiadiazole units and different numbers of K+ selective ligands of triazacryptand (TAC), so as to study their spectral characteristics and response to K+. Among them, PP3 exhibits exceptional responsiveness and selectivity to K+. With a longer conjugated backbone, it shows a longer emission at 628 nm compared to other probes. Especially, the fluorescence intensities of PP3 showed a linear relationship with the concentrations of K+ in the range of 0–250 mM. PP3 has been successfully applied to detect the dynamic equilibrium of potassium ion concentration in living cells. This study proposes and validates the feasibility of the CP-based K+ fluorescence probe design strategy and expands the range of K+ probes, providing a new tool for understanding disease pathogenesis. [Display omitted] • A new design strategy of K+ sensor based on cross-conjugated CPs was proposed. • Six new cross-conjugated CPs K+ sensors were designed and synthesized. • PP3 is the first CPs probe that can detect the dynamic equilibrium of K+ in cells. • The design strategy based on cross-CPs K+ sensor has been proved to be feasible. [ABSTRACT FROM AUTHOR]

Monoamine oxidase A (MAO-A) is involved in various diseases such as heart failure (HF), prostate cancer (PCa), psychiatric disorders, etc. The precise sensing of MAO-A is important to elucidate its function in various biological processes, as well the diagnosis and treatment of related diseases. In this research, we created a brand-new fluorescence probe ANET for the specific detection of MAO-A. Propylamine moiety of ANET was specifically recognized for MAO-A and then the product EHBT was released. A well-calculated p K a value of 8.01 ± 0.02 was achieved for EHBT by pH-dependent spectra. The fluorescence at 700 nm of EHBT was observed at pH 8.0 due to the enhanced intramolecular charge transfer (ICT). The fluorescence intensity of EHBT at 559/700 nm was in a linear relationship with MAO-A concentration in the 0.375–1.50 μg/mL range. The detection limit was 19.8 ng/mL. It is well known that the environment of mitochondria is microalkaline (pH 8.0), however, other organelles are neutral or acidic. So the fluorescence at 700 nm of ANET could be notably turned on by MAO-A in mitochondria. In addition, ANET can selectively accumulate in the mitochondria through powerful electrostatic attractions. Finally, ANET was applied for specific imaging of MAO-A in mitochondria of SH-SY5Y, PC-3, and glucose-deprived (GD) H9c2 cells. [Display omitted] • A probe was developed for Monoamine Oxidases A (MAO-A) based on ICT. • ANET can selectively accumulate in the mitochondria through strong electrostatic interactions. • Since the p K a of EHBT matches the pH in mitochondria, fluorescence of EHBT can be specifically turned on at 700 nm. • ANET was capable of differentiating MAO-A overexpressing cells from other cells. [ABSTRACT FROM AUTHOR]

• Development of a novel red-emitting fluorescent probe (HSA) for the detection of Cys. • The probe can high sensitivity detect Cys with a low LOD. • Successfully verified the experimental results by the theoretical calculation study. • The probe can be used for exogenous Cys monitoring and endogenous Cys cell imaging experiments. Herein, we synthesized a red-emitting fluorescence turn-on probe (HSA) for specific detection of cysteine (Cys) over other biothiols (glutathione (GSH) and homocysteine (Hcy)). The acrylate group was chosen as the recognition site for specific discrimination of Cys. Absorption and emission spectra display a high selectivity towards Cys over GSH/Hcy, organic small-molecule interfering substances and anions, with a high sensitivity towards Cys (0.12 μM) in 1% ethanol-containing PBS buffer solution (25 mM, pH = 7.4). Density functional theory (DFT) and time-dependent DFT (TDDFT) calculations were conducted to clarify the luminescence mechanism of the probe. Furthermore, the probe was successfully applied to the determination of free Cys in human serum and the fluorescence imaging of endogenous Cys in living cells. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A new N-oxide based and turn on fluorescent probe for Fe2+ was developed. • The probe possessed a high selectivity for Fe2+ among various biologically relevant species and fast rapid response. • Monitoring Fe2+ with TPM fluorescence imaging for the first time. Abstract Iron is an essential element for human body, involved in important biochemical processes in the body, especially in biological oxidation. Misregulation of iron levels in the cell is concerned with serious diseases. Here, a novel two photon and turn on NIR-fluorescent probe based ICT for detection of Fe2+ is first reported. The probe exhibited brilliant selectivity and excellent sensitivity (DL = 4.5 μM), rapid response (15 min) and "naked-eye colorimetric sensor" for monitoring of Fe2+. More importantly, the probe was successfully applied to real-time monitor Fe2+ in living cell through two-photon microscopy fluorescence imaging with excitation 680 nm. [ABSTRACT FROM AUTHOR]

Graphical abstract A naphthalimide-indole fused chromophore-based fluorescent probe for instantaneous detection of thiophenol has been developed with a red emission (λ max = 590 nm) and a large Stokes shift (140 nm). Highlights • A naphthalimide-indole fused chromophore-based fluorescent probe for detection of thiophenol has been developed. • This probe exhibited a red emission (λ max = 590 nm) and a large Stokes shift (140 nm) in aqueous media. • This probe displayed a low detection limit (3.6 × 10−8 M) for the detection of thiophenol. • This probe has been successfully applied in real water samples and in living cells. Abstract This work presented a naphthalimide-indole fused chromophore-based fluorescent probe for the detection of thiophenol using 2,4-dinitrobenzene moiety as a sensing unit. This probe was able to work in aqueous media and instantaneously respond to thiophenol (within 5 min). In detecting thiophenol, this probe displayed a red emission (λ max = 590 nm), a 140 nm Stokes shift and a low detect limit (3.6 × 10−8 M). Furthermore, the potential ability for practical applications of this probe has been successfully demonstrated in monitoring thiophenol in living cells and in real water samples. [ABSTRACT FROM AUTHOR]

Cysteine (Cys), homocysteine (Hcy), and glutathione (GSH) are of great importance in many physiological and pathological processes. Due to their similar structure and reactivity of these three biothiols, it is a great challenge to simultaneously distinguish one from another. By virtue of two different fluorescence signals, nitrobenzofurazan ( NBD ) has been proved to be an effective sensing functional group as well as a green fluorophore precursor to construct fluorescent probes for simultaneous discrimination of Cys/Hcy and GSH. However, most of the reported NBD-based fluorescent probes suffered from a poor water-solubility, a slow response, double-wavelength excitation or two interfering fluorescence signals (narrow wavelength separation in λ max Em and/or big difference in Φ Fl ). In this study, we developed a fluorescent probe, MCQ-O-NBD , for simultaneous discrimination of Cys/Hcy and GSH using two matched fluorescent signals (well separated red and green fluorescence and comparable Φ Fl ), which could function in a pure aqueous media with a rapid response under a single-wavelength excitation. This probe exhibited high sensitivity and good selectivity as well as low detection limit, and had been successfully applied to visualize and differentiate Cys/Hcy and GSH in living cells. [ABSTRACT FROM AUTHOR]

A new fluorescent probe tetrahydro[5]helicene-malononitrile derivative was designed and synthesized for selective detection of bisulfite. This fluorescent probe exhibites high response speed and selectivity toward HSO 3 − in PBS solution over other coexisting species accompanied by a distinct fluorescence color change from yellow to blue, which can be visually identified. The probe shows excellent sensitivity to HSO 3 − and the detection limit is as low as 0.27 μM. Once reacted with HSO 3 − , the signal-to-background ratio of fluorescence intensity can reach a 45-folds enhancement and the quantum yield dramatically increases from 1.9% to 52.3%. The response mechanism proved to be a nucleophilic addition reaction of probe with HSO 3 − , which was confirmed by 1 H NMR, Mass titration and theory calculation. Additionally, the preliminary cell imaging experiments demonstrated that the probe could be used for intracellular bisulfite detection. [ABSTRACT FROM AUTHOR]

Hydrazine is a probable human carcinogen and exhibits critical damage to living system. Developing an effective method to detect hydrazine in living samples holds great potential for cancer diagnosis, treatment, and management. In this work, we first fabricate a self-assembled micellar nanoprobe for specific recognition of hydrazine in vitro and in vivo in aqueous solution. The novel probe (T-M) contains a triphenylamine fluorophore as a reporter and malononitrile group as the triggered moiety, then we encapsulated T-M into the hydrophobic interior of an amphiphilic copolymer (mPEG-DSPE) and prepared a novel self-assembled micellar nanoprobe: NanoT-M. The nanoprobe exhibits ultra-sensitivity, high selectivity and good biocompatibility. Furthermore, the nanoprobe shows favourable cellular uptaken and was successfully used to detect intracellular hydrazine in living cells. [ABSTRACT FROM AUTHOR]

Singlet oxygen plays an important role in cancer chemotherapy and biology of reactive oxygen species. In recent years, there are some reports of selective fluorescent probes for detection and imaging of singlet oxygen but the existing probes have some major drawbacks including complicated synthetic routes, poor fluorescence enhancement effects. We report herein that anthracenylmethyl modified non-fluorescent derivatives of fluorescein and rhodamine-6G can reacts with 1 O 2 , which resulted in C C bond cleavage that detach anthracene unit from the fluorophores resulting in strong fluorescence enhancement. These probes exhibit high selectivity and sensitivity in detection and imaging of 1 O 2 in chemical and in living cells. Our approach makes it simple and flexible for development of reaction-based 1 O 2 fluorescent probes for broad application in chemical, biomedical, and environmental sciences. [ABSTRACT FROM AUTHOR]

A novel dual site controlled probe has been developed on the basis of rhodamine and biphenylcarbonitrile unit. The probe showed not only rapid fluorescence response to pH, but also good colorimetric recognition performance for copper ions in the HEPES buffer solution (pH 7.0). The optimal geometric configuration of the probe RhB-H with different structures and the [RhB-H-Cu 2+ ] complex were calculated at B3LYP level by DFT method. On this basis, the response mechanism of pH was analysed combining with the 1 H NMR titration experiment. Moreover, the cytotoxicity studies indicated that the probe had good biocompatibility and low toxicity. Then the probe was also successfully applied on real-time monitoring of the intracellular pH changes by exhibiting different fluorescence and emission intensity. These results demonstrated that the probe could be usefully involved in biological and biomedical research. [ABSTRACT FROM AUTHOR]

A ratiometric fluorescent probe for HSO 3 − was assembled using a pair of Förster resonance energy transfer (FRET)-matchable fluorescent dyes within a single human serum albumin (HSA). In this work, the micro-environment-sensitive dyes B1 and HE were designed and synthesized, wherein B1 located in site II as the FRET donor while HE located in site I as the FRET acceptor and receptor for HSO 3 − . This B1 − HE FRET system exhibited a good efficiency in the sensitive, selective, and ratiometric recognition of HSO 3 − with a detection limit of 99 nM in aqueous media. Furthermore, this B1 − HE system could realize the ratiometric imaging of HSO 3 − in human breast cancer cells. [ABSTRACT FROM AUTHOR]

Due to the prominent photochemical and photophysical properties, the benzofurazan (NBD) fluorophore is a popular platform for constructing fluorescencet sensors. We reported herein a strategy to tune the fluorescence of NBD by modulating the push-pull pairs on the benzene ring, and obtained two novel fluorescent probes, MeS-DMAB and EtS-DMAB , which can selectively detect hypochlorous acid (HOCl) over other reactive oxygen species in aqueous solution with a large stokes shift (∼170 nm). The synthesis and optical properties of these two probes were described. The reaction products of HOCl with MeS-DMAB were isolated and characterized. It turns out that oxidation of the thioether to the corresponding sulfoxide accounts for the turn-on fluorescence. Finally, the probe EtS-DMAB was successfully applied to image exogenous and endogenous HOCl in live cells. [ABSTRACT FROM AUTHOR]

Lipid droplets (LDs) are critical cellular organelles associated with various physiological processes in eukaryotic cells. To visualize LDs and research their complex physiological functions, various fluorescence imaging models including the confocal imaging, the lambda scan imaging and the stimulated emission depletion (STED) super-resolution imaging have been successfully employed in recent years. However, since different fluorescence imaging models have different requirements for fluorescent probes, it is very challenging to employ single fluorescent probe for multimodal fluorescence imaging. Herein, an advanced organic fluorescent probe Lipi-DSBOMe has been sophisticatedly developed for purpose. Featuring with the advantages of high staining selectivity towards LDs, polarity sensitive luminescence, high photostability and low STED saturation intensity, this fluorescent probe is well suited for multimodal fluorescence imaging. For instance, employed with this probe for three-dimensional (3D) confocal imaging to quantitatively determine the change of number of LDs under the oleic acid stimulation, lambda scan imaging to precisely measure the polarity of LDs in different types of cells, and STED imaging to measure the size of LDs with the state-of-the-art resolution (42 nm). In overall, employing this single fluorescent probe for multimodal fluorescence imaging has allowed to provide abundant information about LDs, thus effectively promoting the LDs biology studies. [Display omitted] • An advanced fluorescent probe was developed for multimodal imaging of LD. • Abundant information about LD could be provided by multimodal fluorescence imaging. • The highest resolution (42 nm) of LD was achieved in STED super-resolution imaging. [ABSTRACT FROM AUTHOR]

A novel fluorescent probe O-hNRSel based on tetralin-xanthene fused dye O-hNR was designed and synthesized by introducing 2,4-dinitrobenzenesulfonate functionality. This probe is able to detect selenocysteine (Sec) with rapid response time (2 min) and a large fluorescence enhancement at 624 nm (124-fold). O-hNRSel exhibited selective response to Sec over many other analy and high sensitivity with the detection limit as low as 17 nM. Furthermore, O-hNRSel has been used for fluorescent imaging of Sec in living cells with good biocompatibility. [ABSTRACT FROM AUTHOR]

New phenothiazine appended BODIPY derivative has been synthesized and characterized for the determination of hypochlorite in live cells. The fluorescent probe has exhibited 72 fold fluorescence enhancement upon addition of hypochlorite over other reactive oxygen species. Further, the studies proved that the probe has ability to detect the hypochlorite even at extremely low level (4.1 nM). Having less cytotoxicity and negligible auto-fluorescence, the probe was successfully used to monitor external addition and internal secretion of hypochlorite in RAW 264.7 cells. [ABSTRACT FROM AUTHOR]

It is still challenging to simultaneously distinguish general biothiols (cysteine (Cys), homocysteine (Hcy) and glutathione (GSH) etc .) in complex redox environments, due to the lack of reliable and convenient method. Although a number of fluorescence and/or UV–vis absorption based measurements have been employed for single or multiple biothiols detection, few of them is capable of recognizing each biothiol with individual signal at the same time. We present a one-step obtained selenadiazole derivative ( 1 ) to distinguish Cys, Hcy and GSH, which not only can produce three new kind of fluorescent compounds, but also simultaneously induce different “turn-on” fluorescence emission and red-shifted absorption signals for discriminating each biothiol. With a series of systematically analyses elucidate that probe 1 possesses high sensitivity and good selectivity for the three biothiols. Furthermore, the detection mechanism was also verified via a stepwise selenium–nitrogen (Se N) bond cleavage process of probe 1 interacting with each biothiol. In the application of tracking in vitro and in vivo biothiols, probe 1 can be acted as a dual-mode fluorescent and colorimetric platform. [ABSTRACT FROM AUTHOR]

A fluorescence probe (HBM) based on conjugation of 3′-formyl-4′-hydroxy-4-biphenylcarbonitrile to 2,4-dinitrophenylhydrazune for the detection of hypochlorite has been developed. The probe exhibited a highly sensitive and selective response toward hypochlorite (ClO − ) with a low detection limit of 49 nM. The sensing mechanism was considered that the hypochlorite triggered oxidative hydrolysis of probe HBM and the cyanobiphenyl fluorophore was released, which also have been evidenced by the MS analysis. Most notably, the response time of the probe HBM to the OCl − is only a few seconds. The probe was also successfully applied to fluorescence imaging of OCl − in the living cells. [ABSTRACT FROM AUTHOR]

The cell permeable small fluorescent organic molecules possessing RNA-specific binding property were synthesized for the study of structural influence on two determining factors of binding affinity and specificity. Similar investigations are scarce in the field of RNA-specific binding ligand development based on a systematic structural change of small molecules. The newly developed and structurally simple ligands show much higher RNA-binding affinity (equilibrium binding constant: PI1 , K = 4.50 × 10 5  M −1 ; PI2 , K = 4.48 × 10 5  M −1 ) than that of a well-studied RNA-selective dye E36 (K = 0.89 × 10 5  M −1 ) by the introduction of an aminoethylpiperidine group on the quinolinium scaffold. In addition, the in vivo study of live cell imaging (human prostate cancer cells) indicated that these small molecules are able to provide strong interaction signals when binding with RNA in the region of nucleolus and cytoplasm. The interaction specificity of the molecule towards RNA is found much higher than other types of nucleic acids, which was further supported by the digest tests with ribonuclease (RNase). The experimental results of the present study not only provide important cues on the fluorescent signaling, binding affinity, and specificity advancement with the small RNA-specific binding ligands through structurally refinement of molecular scaffolds, but also give complementary information in searching lead ligands for targeting RNA sequence using high-throughput compound screening techniques and molecular modeling studies. [ABSTRACT FROM AUTHOR]

A new fluorescein-based probe ( Py-F ) was designed and synthesized to develop an optical and fluorescent sensor for biological thiols. Py-F possessed the thiol-responsed disulfide group and displayed selectivity and sensitivity for glutathione (GSH) and cysteine (Cys) over homocysteine (Hcy) in the CH 3 CN/PBS buffer solution, and the fluorescence detection limit was calculated to be 0.12 μM and 0.13 μM, respectively. Besides, the recognition mechanism was explained by density functional theory (DFT) calculation, and confirmed by mass spectroscope measurement. Furthermore, the thiols detection application in cellular imaging assays indicated that the probe has appreciable cell permeability and can serve as a fluorescent probe for detecting biothiols in living cells. [ABSTRACT FROM AUTHOR]

A new Schiff base tcph, derived from 2-thiophene carboxylic acid hydrazide, has been synthesized and characterized by various spectroscopic techniques. The molecular structure of the compound has also been determined by X-ray crystallography. The tcph acts as a selective Al 3+ and F − induced OFF-ON-OFF type of probe in aqueous media. The 1:1 binding stoichiometry between probe and Al 3+ has been established from Job’s plot and further supported by ESI–MS studies. The limit of detection of Al 3+ ions is determined by 3σ methods, which is found to be 1.35 × 10 −9 M. The coordination environment for the tcph-Al 3+ complex is delineated by NMR titration and DFT calculations. Detailed insights of probe–metal interaction mechanism have been studied by density functional theory (DFT) as well as time dependent–DFT calculations. MTT assay of the probe on live SiHa cells suggests no serious cytotoxicity in cells even at higher concentration. The probe tcph and its tcph-Al 3+ complex have also been successfully applied to detect Al 3+ and F − ions in living cells (SiHa cells), respectively. [ABSTRACT FROM AUTHOR]

An imidazo[1,5-α]pyridine-based fluorescence probe NIPY-DNP with a large Stokes shift (193 nm) has been successfully developed for highly selective, sensitive and rapid detection of H 2 S. The selective deprotection of 2,4-dinitrophenyl ether group of NIPY-DNP by H 2 S led to a dramatic fluorescent enhancement (273-fold) at 505 nm within 5 min in PBS buffer solution. The sensing mechanism is proposed on the basis of the thiolysis reaction by H 2 S, which has been confirmed by HPLC and HRMS. The detection limit is 0.36 μM, which is superior to the other reported H 2 S probes. Additionally, cell imaging studies demonstrated that NIPY-DNP could be used to visualize H 2 S in living cells. [ABSTRACT FROM AUTHOR]

Hypochlorous acid (HOCl) plays a crucial role in the immune defence against invasive bacteria and other biological processes in living organisms. A turn-on fluorescent probe ( PZ-HA ) for sensitive detection of HOCl was developed. After the addition of HOCl, an approximately 80-fold enhancement in fluorescence intensity at 605 nm was observed. PZ-HA has a large Stokes shifts that can effectively avoid the self-absorption of the fluorescence. In addition, PZ-HA has excellent properties, including fast responsive, good selectivity and low cytotoxicity and well membrane-permeability. The potential of the probe as biosensor for HOCl was demonstrated by imaging of exogenous and endogenous HOCl in living cells. Further, the probe was applied to the fluorescence imaging of HOCl in zebrafish. Therefore the probe is expected to be useful for the accurate detection of HOCl in complex biosystems. [ABSTRACT FROM AUTHOR]

By employing the oxidation property of hypochlorite (OCl − ), a new probe based on coumarin dye and an OCl − -specific reactive moiety of hydrazide group was designed and synthesized. The probe rendered turn-on type fluorogenic response toward OCl − via hypochlorite-triggered oxidative hydrolysis of hydrazide to release strongly fluorescent coumarin. Most notably, the probe showed sufficiently satisfactory selectivity to OCl − over other oxidants, and high sensitivity with approximate 18-fold fluorescence enhancement at nanomolar level. Moreover, the fast detection of OCl − could be realized by the probe with only 30 s. The interaction mechanism has been proposed and further confirmed by the changes in electrospray ionization (ESI) mass spectra. The probe was also successfully applied to fluorescence imaging of OCl − in its vitro macrophage cells. [ABSTRACT FROM AUTHOR]

Herein we report a new carbazole-benzo[e]indolium dye (CEBI) as a ratiometric fluorescent and chromogenic probe for sulfite (SO 3 2− ) detection based on intramolecular charge transfer (ICT) mechanism. Upon treatment with SO 3 2− , the probe CEBI displayed a remarkable fluorescence ratiometric response (∼560-fold fluorescenc enhancement) together with a color change from red to weak red and a large shift (135 nm) in emission wavelength. The experimentally observed changes in the spectral features of the probe upon addition of SO 3 2− were systematically studied using high resolution electrospray ionization mass spectrometry (HR-ESI–MS), proton nuclear magnetic resonance ( 1 H NMR), and time-dependent density functional theory (TDDFT) calculations. We found a linear relationship between the ratio of fluorescence intensities at 465 nm and 600 nm ( F 465 /F 600 ) and SO 3 2− concentration over the range of 0–40 μM with a detection limit of 0.025 μM. Moreover, the novel probe demonstrated fluorescence imaging of SO 3 2− in living cells and zebrafish, suggesting its potential in clinical diagnostics. [ABSTRACT FROM AUTHOR]

Hypoxia may improve the biological activity of nitroreductase (NTR). The development of effective methods for monitoring the activity of NTR plays an important role in the early diagnosis of tumors. Toward this goal, we have developed a new two-photon fluorescence NTR probe CoNO 2 -HY with fast response, high sensitivity and selectivity, and a large turn-on fluorescence signal. The probe CoNO 2 -HY could monitor endogenous NTR in living HeLa cells. Importantly, the probe CoNO 2 -HY is successfully applied to detect the endogenous NTR in the tumor tissue of mice with the penetration depth up to 90 μm. [ABSTRACT FROM AUTHOR]

A new fluorescent probe ( ABPA ) based on 1,8-naphthalimide, which designed on the “ receptor 1 -fluorophore-spacer-receptor 2 ” model and employed conjugated addition/cyclization sequence mechanism for Cys detection was reported. The probe shows high selectivity and sensitivity for cysteine (Cys) over other amino acids including the similar structured homocysteine (Hcy) and glutathione (GSH). It displays a highly sensitive fluorescence emission to Cys with a detection limit of 0.12 μM (S/N = 3), which is far below the normal level of Cys (30–200 μM) in living cells. Furthermore, ABPA was successfully applied to bioimage intracellular Cys in living cells with low cytotoxicity. [ABSTRACT FROM AUTHOR]

Herein, we report a novel Schiff base “turn-on” fluorescent and chromogenic probe N′-(3-(benzo[d]thiazol-2-yl)-2-hydroxybenzylidene)-4-(dimethylamino)-benzohydrazide (BHDB) for CN − detection under physiological pH, based on nucleophilic reaction of imine ( CH N ) and CN − , exhibiting almost 66-fold fluorescence increase and a remarkable color change from colorless to yellow. The experimentally observed changes in the spectral properties of the probe upon addition of CN − were systematically studied using high resolution electrospray ionization mass spectrometry (HR-ESI-MS), proton nuclear magnetic resonance ( 1 H-NMR), and time-dependent density functional theory (TDDFT) calculations. Using the fluorescence spectra changes, we found a detection limit for CN − of 0.15 μmol L −1 , far lower than the maximum permissive level of CN − (1.9 μmol L −1 ) in drinking water recommended by World Health Organization (WHO). Moreover, the novel probe demonstrated fluorescence imaging of CN − in living cells and zebrafish, suggesting its potential in clinical diagnostics. [ABSTRACT FROM AUTHOR]

A new fluorescent probe ( TRDM-F ) based on a molecular chain of open-loop maleic anhydride, rhodamine B and fluorescein was designed, synthesized and evaluated to develop a chemosensor. Photochemical studies show that fluorescence properties of TRDM-F are dominated by fluorescein group in the pH range of 2–10. UV–vis absorption and fluorescence spectroscopic studies further display a high selectivity towards Cys over GSH/Hcy and other amino acids and a high sensitivity towards Cys (0.088–270 μM) with 95-fold fluorescence enhancement in a HEPES buffer solution (10 mM, pH = 7.4) containing 20% MeCN at room temperature. We further demonstrated that the proposed method was satisfactorily applied to the discrimination of Cys in living Hela cells with low cell toxicity. [ABSTRACT FROM AUTHOR]

A fluorescent probe ( DBT ) based on conjugation of 2,3-dimethylbenzo[ d ]thiazol-3-ium iodide to 3-(benzo[ d ]thiazol-2-yl)-2-hydroxy-5-methylbenzaldehyde for the detection of sulfur dioxide derivatives (HSO 3 − /SO 3 2− ) has been developed. DBT exhibits highly selective colorimetric and ratiometric fluorescence dual response to HSO 3 − with a fluorescence detection limit of 3.50 × 10 −7 M. The HSO 3 − sensing mechanism was confirmed to undergo nucleophilic addition of HSO 3 − to alkene double bond of DBT as evidenced by 1 H NMR and HRMS analysis. The probe is MCF-7 cell permeable and applicable for fluorescence imaging of exogenous and intrinsically generated intracellular SO 2 derivatives in the living cells. Fluorescence co-localization studies reveal that DBT is a mitochondria-targetable fluorescent probe. Thus, DBT has potential application for exploring the role played by SO 2 derivatives in biology. [ABSTRACT FROM AUTHOR]

Copper is an essential element in living organisms and the monitoring of copper ions in aquatic environments and biological systems is of great significance. Inspired by a family of visible light responsive photoswitchable compounds, we report here a fluorescent probe (HTI-Q) for Cu2+ with excellent selectivity, high sensitivity, and a limit of detection (LOD) of ca. 0.02 μM. While the central carbon-carbon double bond of HTI-Q is photoisomerizable between the Z and E configurations, it is locked upon binding with Cu2+ into the E configuration, resulting in a large bathochromic shift (102 nm) and ratiometric fluorescence changes. Different sensing modes were demonstrated including in mixed solvents, a two-phase sensing system containing cation exchanger, and fluorescent nanoprobes containing a reference dye. The absorbance change of HTI-Q upon 470 nm light illumination also depended on the concentration of Cu2+. HTI-Q-based sensors were successfully applied to determine Cu2+ in real water samples with excellent recovery. Further, fluorescent nanoprobes incorporating HTI-Q were successfully applied to image endolysosomal Cu2+ changes upon external stimulation. [Display omitted] • A photoswitchable Cu2+ probe (HTI-Q) was proposed for the first time based on hemithioindigo. • HTI-Q offered tunable sensitivity, high selectivity, and several different optical sensing modes. • Nanoprobes containing HTI-Q were successfully applied for subcellular fluorescence imaging in the endolysosomes. [ABSTRACT FROM AUTHOR]

Gene expression and regulation in which RNA is an essential participant can be visualized by imaging RNA with fluorescent probes. However, most of the reported fluorescent probes for RNA have defects such as short emission wavelength, small Stokes shift, poor selectivity, low sensitivity, and poor membrane permeability. Herein, a NIR (710 nm) cationic fluorescent probe PCTP with D-π-A structure and large Stokes shift (285 nm) using 9-phenylcarbazole as an electron donor and pyridinium salt as an electron acceptor was designed and synthesized. Titration experiments and enzyme treatment experiments demonstrate that PCTP can differentiate RNA from DNA in solution and cells, the fluorescence intensity of PCTP increases by a maximum of 52.2 times after binding to RNA and the detection limit is 2.17 μg/mL, showing high selectivity and sensitivity to RNA. Furthermore, with low cytotoxicity, good biocompatibility and high photostability, PCTP is able to trace 4T1 cell proliferation in vitro to 9 generations and trace 4T1 cell in mice for 22 days. The probe provides a potential tool for RNA imaging and long-term cellular tracing. • a NIR (710 nm) cationic fluorescent probe PCTP with D-π-A structure and large Stokes shift (285 nm) was designed and synthesized. • The fluorescence intensity of PCTP increases by a maximum of 52.2 times after binding to RNA and the detection limit is 2.17 μg/mL. • PCTP can differentiate RNA from DNA in solution and cells, showing high selectivity and sensitivity to RNA. • PCTP is able to trace 4T1 cell proliferation in vitro to 11 generations and trace 4T1 cell in mice for 22 days. [ABSTRACT FROM AUTHOR]

A supramolecular fluorescent probe based on double-cavity nor-seco -cucurbit[10]uril (ns -Q[10]) was constructed using the non-covalent host-guest interactions between ns -Q[10] and positively charged Astrazon Pink FG (APFG). The intramolecular charge transfer (ICT) effect induces the APFG@ ns -Q[10] probe to emit strong orange-red fluorescence. APFG@ ns -Q[10] exhibits desirable optical properties and low toxicity, and has been successfully applied to the imaging of HK2 and HeLa cells. When APFG@ ns -Q[10] interacts with ClO-, the C C double bond in APFG is oxidized and the molecule is cleaved, which leads to the fluorescence is quenched. The specificity and sensitivity of APFG@ ns -Q[10] to ClO- allows it to be used for the detection and tracking of ClO- in cells. APFG@ ns -Q[10] demonstrates good biocompatibility, which is an excellent foundation for its application in cell imaging. • A supramolecular fluorescent probe based on ns -Q[10])was constructed using the non-covalent host-guest interactions. • APFG@ ns -Q[10] exhibits desirable optical properties and low toxicity, and was applied to the cell imaging. • The specificity and sensitivity of APFG@ ns -Q[10] to ClO- allows it to be used for the detection of ClO- in cells. [ABSTRACT FROM AUTHOR]

A ratiometric fluorescent probe ( NR ) for HOCl based on a new naphthalimide-rhodamine platform involving through-bond energy transfer (TBET) process is presented. Rhodamine B thiohydrazide and naphthalimide derivative were linked to form a structure of monothio-bishydrazide. Free NR only emitted the fluorescence of naphthalimide. The treatment of NR with HOCl converted the monothio-bishydrazide into 1,2,4-oxadiazole. As a result, naphthalimide donor and rhodamine acceptor were connected with electronically conjugated bonds, and the spiro ring of rhodamine was opened. Hence, a typical TBET process took place, resulting in the increase of rhodamine emission at 582 nm as well as the decrease of naphthalimide emission at 532 nm. I 582 /I 532 ratios showed desirable HOCl-dependent performance and responded linearly to minor changes of HOCl concentration (0–5 μM). The detection limit was determined to be 14.5 nM. NR exhibited high selectivity, rapid response and low cytotoxicity. Moreover, NR has been employed for the imaging of artificially loaded HOCl and endogenously produced HOCl with satisfying results. Therefore, NR may act as a practical molecular tool for monitoring HOCl fluctuations in biological systems. [ABSTRACT FROM AUTHOR]

Palladium is significant in chemistry, biology and environmental science, while as a toxic metal, it could have adverse effects on our health and the environment. It is thus critical to monitor the changes of Pd (II) in living cells. Here, we developed a new colorimetric and fluorometric probe ( TP1 ) based on palladium(II)-involved reactivity. Compared with the reported Pd (II) sensors, TP1 was the first alkyne compound fluorescent probe with excellent water-solubility for Pd 2+ , which was via catalytic-depropargylation to form oxime for the detection of Pd 2+ within a rapid response time 80 s. The detection limit of TP1 toward Pd(II) was estimated as 0.47 μM. In addition, the ability of the TP1 to detect Pd(II) in living cells (HepG2 cells) has been also proven. These results indicated that TP1 was a highly sensitive turn-off Pd(II) dye with promising biological applications. [ABSTRACT FROM AUTHOR]

In this study, a new compound 2-amino-3-[(4-(1H-phenanthro [9,10-d] imidazol-2-yl) phenyl methylene) amino]-2-butenedinitrile (probe 1 ) as a simple fluorescent probe for hypochlorous acid has been synthesized and characterized. It exhibited high selectivity and sensitivity as hypochlorite sensor in mixed aqueous medium. NMR and mass spectral analysis showed that the probe reacted with the hypochlorite ion through de-diaminomaleonitrile reaction which disrupted the ICT mechanism by breaking the donor and acceptor linkage resulting in a remarkable enhancement of the emission intensity. In addition, the probe worked excellently within a wide pH range of 4 to 10 and the detection limit was found to be 1.4 × 10 −2 μM. The cell experiments showed the good cell-membrane permeability of probe, and it could be used to image exogenous HOCl. [ABSTRACT FROM AUTHOR]

In this work, a novel fluorescent probe ( DOCOU ) based on coumarin has been designed and synthesized for the detection of biothiols. In this probe, a new hydroxy-coumarin-based fluorescent dye, HOCOU , was firstly used as the fluorophore and 2, 4-dinitrobenzenesulfonyl (DNBS) group was incorporated as both a recognition unit and a fluorescence quencher. The probe DOCOU shows high selectivity and sensitivity for Cys, Hcy, and GSH over other amino acids and interfering species under physiological conditions. Mechanism study indicated that the remarkable fluorescence turn-on response is induced via a thiolate mediated SNAr reaction. Furthermore, DOCOU features good linearity ranges with low detection limit of 17.1 nM for Cys, 14.5 nM for GSH, and 40 nM for Hcy, respectively. In addition, the probe was successfully applied for imaging biothiols in Hela cells with low cytotoxicity. [ABSTRACT FROM AUTHOR]

We report a novel turn-on two-photon fluorescent probe ( TPNF ) for detecting formaldehyde based on aza-Cope rearrangement and intramolecular charge transfer (ICT). The probe, containing a 1,8-naphthalimide dye with a homoallylamino group, has was shown with high selectivity, sensitivity and low cytotoxicity and it was capable of detecting formaldehyde in live cells. Moreover, a time-dependent density functional theory (TD-DFT) calculation was performed to demonstrate the turn on mechanism of the probe via ICT effect. Finally, a zebrafish larvae imaging experiment reveals that TPNF displayed a significant signal change when treated with FA in vivo. These results indicated that TPNF is a promising tool in more biomedical researches. [ABSTRACT FROM AUTHOR]

A near-infrared fluorescent probe based on benzo[a]phenoxazine containing o -phenylenediamine group as reactive site was designed and synthesized. The titration experiment showed that the probe gave colorimetric response towards sodium nitrite with the absorption maxima at 630 nm and 542 nm in pH = 5.0 disodium hydrogen phosphate-citric acid buffers containing 30% DMSO; its emission was located in 590–820 nm with the 9.1-fold fluorescent enhancement under excitation at 580 nm. Moreover, the probe can detect nitrite quantitatively in a concentration range of 0.0–26.0 μM and the detection limit is as low as 45 nM. The salient features of this method are high sensitivity and selectivity, fast detection and low detection limit. Fluorescence confocal imaging experiments with V79 and HeLa cells indicate that the probe has the potential application in quantitative detection exogenous nitrite level for in cellular imaging. [ABSTRACT FROM AUTHOR]

An efficient and highly selective dihydrazone based fluorescent probe N ′, N ′–bis((2–hydroxynaphthalen–1–yl)methylene)malonohydrazide (H 2 nmh), has been synthesized for selective detection of Al 3+ ions and characterized by different physico–chemical and spectroscopic techniques. The probe shows an enhanced fluorescence in the presence of Al 3+ ions in ethanol–water (2:3 v/v) solution which is not observed in the presence of other cations (Na + , K + , Mg 2+ , Ca 2+ , Mn 2+ , Fe 3+ , Co 2+ , Ni 2+ , Cu 2+ , Zn 2+ , Pb 2+ , Cd 2+ and Hg 2+ ). The binding modes of H 2 nmh with Al 3+ were studied by UV–vis, fluorescence and 1 H NMR titrations. The probe act as dibasic hexa–dentate ligand and interacts with two Al 3+ ions with a binding constant K B = 5.74 × 10 9 M −1 and detection limit 5.78 × 10 −8 M. Detailed insights of probe–metal interaction mechanism were studied by mean of density functional theory (DFT) as well as time dependent–DFT calculation. MTT assay on live MCF–7 cells has been performed to evaluate the cytotoxicity of the probe which suggests viability of the probe to MCF–7 cells even at higher concentration (100 μM) with no serious cytotoxicity in cells. Live cell imaging study clearly indicates that the accumulation of Al 3+ in the cytoplasm of cells can be detected by H 2 nmh. [ABSTRACT FROM AUTHOR]

Fluorescence imaging plays an increasingly important role in biomedicine field due to its superior sensitivity and selectivity along with dynamic, real-time, in situ monitoring the occurrence and development of biological events. Therefore, it is crucial to construct a near-infrared (NIR) fluorescent molecule with excellent optical properties. Herein a NIR robust out mitochondria-targeting dye NN has been designed, synthesized and characterized, whose fluorescence properties are easily adjusted by changing the substitution position of the nitro group at the benzene ring in this fluorescent dye. NN was a unique fluorescence-enhanced nitro dye with high fluorescence quantum yields∼0.17, a large Stokes shift∼120 nm and stable chemical structure. Encouraged by this, a novel fluorescent probe NN - Sec based on intramolecular charge transfer (ICT) was constructed by grafting NN with a selenocysteine (Sec) recognition group 2,4-dinitrobenzenesulfonyl (DNBS), and it exhibited a targeted ability with great sensitivity and selectivity. Subsequently, the probe was used for NIR imaging in living cells and mice, and deep imaging results further illustrate its potential application in biosystems. The successful design of NN and NN - Sec offer a valuable theoretical basis and technical support for investigating the occurrence and development of Sec-related diseases. • A novel NIR fluorescent dye NN bearing nitro was reported with an enhanced fluorescence quantum yields. • The recognition group 2,4-dinitrobenzenesulfonyl of Sec was grafted with dye NN to synthesize fluorescent probe NN-Sec. • ANN-Sec can detect Sec in live cells and mice by high sensitivity and selectivity, accompanied by bright NIR emission. [ABSTRACT FROM AUTHOR]

Mitochondrial G-quadruplex structure is an important element for regulating mitochondrial function and is expected to be a potential target for the treatment of some major diseases. Currently, compounds that can track mitochondrial G-quadruplexes are still limited, making it difficult to investigate their functional mechanisms in depth. In this study, a new compound named ThT-S was prepared through structural modification of Thioflavin T (ThT). ThT-S not only has higher selectivity for G-quadruplex structure, but also can rapidly enter mitochondria in live cells with high specificity. ThT-S also has the advantages of good optical stability and low cytotoxicity. These properties make ThT-S a promising sensor for mitochondrial G-quadruplex studies. This study also provides new insights into the structural design of mitochondrial G-quadruplex-targeting compounds. [Display omitted] • A new ThT derivative named ThT-S has been designed. • ThT-S has higher selectivity for G-quadruplex structure. • ThT-S is highly targeted to mitochondria and stains rapidly. • ThT-S can be used for in situ imaging of mitochondrial G-quadruplexes. [ABSTRACT FROM AUTHOR]

A new rhodamine B-based fluorescent probe ( Probe-M ), namely N-(2-(3′,6′-bis(diethylamino)-3-oxospiro[isoindoline-1,9′-xanthen]-2-yl)ethyl)-3,5-bis(2,5-dioxo-2,5-dihydro-1H-pyrrol-1-yl) benzamide, was designed and synthesized to develop a fluorescent sensor for glutathione (GSH). Probe-M displayed excellent selectivity and sensitivity for GSH over many other amino acids in an EtOH/HEPES buffer solution. The application of GSH in cellular imaging experiments indicated that the probe has appreciable cell permeability and is highly responsive to changes in the GSH level. As a result, Probe M can serve as a fluorescent probe for detecting GSH in living cells. [ABSTRACT FROM AUTHOR]

G-quadruplexes, one of the most significant secondary structure of nucleic acid, are formed by stacking G quartets, which received broad interests due to their involvement in telomere function, gene transcription and recombination. As for ligand, better selectivity for G-quadruplex against other DNA or RNA structures and higher ability to stabilize G-quadruplex are necessary. In addition, developing a new probe to recognize G-quadruplex is desired for utilizing G-quadruplex structure to relevant biological processes. In this study, we report a Cy5 labelled ligand (named PDP-Cy5) developed as a near-infrared fluorescent ligand for G-quadruplexes both in DNA and RNA. The results indicated that PDP-Cy5 selectively induced the formation of intramolecular G-quadruplexes with strong binding affinity. Furthermore, this Cy5 labelled ligand can effectively stabilize G-quadruplexes. Moreover, the direct visualization of G-quadruplexes in gel, even on cell level is realized by using PDP-Cy5. [ABSTRACT FROM AUTHOR]