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A novel rhodamine-based colorimetric and fluorescent sensor for Hg 2+ was reported. In CH 3 CN/H 2 O (1/99, v/v), the sensor showed high selectivity and sensitivity to Hg 2+ by an emerging absorption peak at 565 nm and a 32-fold fluorescence enhancement at 586 nm with vivid color changes. The absorbance and fluorescence maxima increased linearly with the concentration of Hg 2+ in the range of 0–90 μM. The colorimetric and fluorescent detection limits were 6.36 μM and 60.78 nM respectively. The sensor could work in a nearly neutral pH span of 6.01–8.57 and exhibited excellent interference immunity and low cytotoxicity. A 1:2 sensor-Hg 2+ complex formed with a binding constant of 2.89 × 10 8 M −2 . A new sensing mechanism was proposed. The sensor was successfully applied in real sample assay and living cell imaging. Furthermore, the sensor could be supported in low cost cellulose discs for signaling Hg 2+ in 100% aqueous solution. [ABSTRACT FROM AUTHOR]

Aptamer-functionalized fluorescent silver nanoclusters (Ag NCs) possessing specific recognition ability of aptamer and fluorescence emissions have been developed for applications in biorelated areas. However, only one color emission hampered their further use in multiplexed analysis. To address this issue, AS1411 aptamer-tagged Ag NCs with green color emissions and MUC 1 aptamer-tagged Ag NCs with yellow color emissions were synthesized by one-pot approach in this work. With the rational design of the DNA template and optimization of the synthetic buffer, as well as the NaBH 4 -to-Ag + ratio, the growth time and purity of the obtained aptamer-functionalized Ag NCs were improved. Under the optimal conditions, the quantum yields of AS1411 aptamer-functionalized green Ag NCs and MUC 1 aptamer-functionalized yellow Ag NCs were 20.33% and 8.65% with 9,10-diphenyl anthracene and fluorescein as the reference standards, respectively. The green and yellow emission properties of Ag NCs were related to the surface oxidation states of the Ag NCs. Furthermore, the binding ability of AS1411 aptamer and MUC 1 aptamer to cancer cells enabled specific cellular imaging. Aptamer-functionalized Ag NCs with multicolor emissions could broaden the applications of Ag NCs in multiplexed analysis and multicolor imaging of tumor cells, especially with the selection of more targeted aptamers. [ABSTRACT FROM AUTHOR]

A novel fluorescent sensor for Zn 2+ based on 8-oxalamidoquinoline (OAQ) was designed and synthesized. OAQ behaves high selectivity to Zn 2+ accompanied by remarkable emission enhancement (32 folds) at 490 nm upon binding Zn 2+ in buffer aqueous solution at pH 7.2. The results show that a 1:1 complex was formed and the apparent association constant of OAQ/Zn 2+ complex was calculated to be 2.5 × 10 5 M −1 . The detection limit was gained to be 2.0 × 10 −8 M. Furthermore, the fluorescent signals of OAQ are utilized to construct an INHIBIT logic gate at the molecular level. Additionally OAQ was successfully used for fluorescence imaging in living yeast cells. [ABSTRACT FROM AUTHOR]

Direct visualization of Nitroxyl (HNO) release is currently not feasible for all chemical and biological systems, limiting the understanding of its biological and pharmaceutical activities. To address this issue, N -hydroxydansylamide was developed as the first fluorescence turn-off HNO donor that efficiently releases HNO with a fluorescence turn-on probe. Under physiological conditions, the HNO release was observed with a half-life of 19.86 min. The decomposition of N -hydroxydansylamide yielded a fluorescent dansyl-based sulfinate species. Specifically, the concentration of HNO released was successfully monitored based on the fluorescence signal with a limit of detection of ~ 0.55 µM. Particularly, HNO releasing can be sensed without any depletion of the HNO source. Finally, cellular imaging was also achieved to demonstrate the HNO release derived from N -hydroxydansylamide. Therefore, HNO release profiles in terms of kinetics, dose, and the site can be monitored through real-time fluorometric analysis or imaging-based studies, providing a novel platform to explore HNO biology. [Display omitted] • N -hydroxydansylamide can efficiently release HNO with a fluorescent probe. • The real-time HNO release was firstly probed based on fluorescence signal. • Cellular imaging of HNO release was achieved using N-hydroxydansylamide donor. • HNO releasing can be sensed without any depletion of HNO source. [ABSTRACT FROM AUTHOR]

In the current study, we designed and prepared five fluorogenic probes (β-GlcNAc-FC, β-GlcNPr-FC, β-GlcNBu-FC, β-GlcNVa-FC and β-GlcNAc-Bn-FC) for the detection of O-GlcNAcase in live cells. Among these probes, β-GlcNAc-FC was found to be the best fluorogenic substrate for O-GlcNAcase. In addition, β-GlcNAc-FC was able to monitor cytosolic and nuclear O-GlcNAcase in cells. By using this probe, we found that O-GlcNAcase activity in AGS cells is higher than those in Capan-1 and HaCaT cells. Also, we observed that fluorescence signals arising from β-GlcNAc-FC are very low in cells cultured under glucose deprivation conditions and gradually increases when the concentration of glucose in culture media increases up to 10 mM. Furthermore, ER and mitochondrial stresses caused by respective treatment with tunicamycin and FCCP did not affect O-GlcNAcase activity, as judged from the observation that the fluorescence intensity arising from β-GlcNAc-FC in cells exposed to these stresses was quite similar to that in cells cultured under normal conditions. Taken together, the findings indicate that β-GlcNAc-FC is a useful fluorogenic probe to determine the level of O-GlcNAcase activity in live cells. • A fluorogenic probe for detection of O-GlcNAcase is developed. • A fluorogenic probe is utilized to image O-GlcNAcase in live cells. • The probe is utilized to assess the effect of cellular stress on O-GlcNAcase activity. [ABSTRACT FROM AUTHOR]

Based on fluorescein, a novel water-soluble and reversible fluorescent probe (Flu-Py) was designed and synthesized for the sequentially “ON–OFF–ON” fluorescent detection of Al 3+ and F − in concentration range of 0–10 μmol L −1 and 0–30 μmol L −1 , respectively, with high sensitivity and excellent selectivity. The detection limits for Al 3+ and F − were 0.092 μmol L −1 and 0.112 μmol L −1 , respectively. The binding mode and sensing mechanism of Flu-Py with Al 3+ was verified by density functional theory (DFT) and time dependent density functional theory (TDDFT) calculation. The “ON-OFF–ON” fluorescent property of Flu-Py upon the addition of Al 3+ and F − was utilized for the imaging of living cells. [ABSTRACT FROM AUTHOR]

A novel aggregation-induced emission (AIE) active linear conjugated bis-Schiff base compound, ( E )- N , N ′-bis(4-( Z )-2-(4-butoxyphenyl)-1-cyanovinylphenyl)-1,4-benzenebismethaneimine ( 4 ) containing α-cyanostilbene unit was designed, synthesized and characterized. The distinct change of color and/or fluorescence emission of 4 + Hg 2+ in tetrahydrofuran (THF) and THF/water solution provided a simple and easy discrimination way for Hg 2+ by “naked eye” or using a UV lamp. The aggregating patterns of 4 were applied to explain the mechanism of sensing. The as-synthesized sample showed comparatively high selectivity and sensitivity to Hg 2+ through fluorescence “turn-on” response with a low detection limit (3.4 × 10 −9 M in THF, 2.4 × 10 −7 M in THF/water). The results implied that the as-made sample could effectively act as Hg 2+ sensor not only in THF and THF/water but in living cells. [ABSTRACT FROM AUTHOR]

Many rhodamine B probes for metal ions and anions showing “orange” fluorescent have attracted a tremendous amount of attention. Herein a rhodamine B-based fluorescent probe 1 showing “green” fluorescence emission in the presence of Hg 2+ was first reported. Self-assembled aggregation was proved to be the crucial factor for the green emitting fluorescence by means of resonance light scattering spectra, fluorescence spectra, ESI mass spectral analysis and SEM image. The probe 1 was developed as a excellent Hg(II)-selective green fluorescence agent in ethanol/HEPES buffer media (v/v = 3:7, pH 7.3) with a detection limit of 0.09 μM. Meanwhile, the green fluorescence of 1 -Hg 2+ can be quenched severely by Cys but not for GSH, S 2− , SO 4 2− , SO 3 2− , CN − , CO 3 2− and HCY. The sequential switching effect for Hg 2+ and then Cys has been achieved in aqueous media and bioimaging with satisfactory results. [ABSTRACT FROM AUTHOR]

A rhodamine derivative ZP1 , appended with two 1,2,3-triazole moieties via a diaminopropyl linker, is a chromogenic and fluorogenic sensor for Zn 2+ . In the presence of Zn 2+ , a colorless solution of ZP1 becomes pink with a maximum absorption of 555 nm and a large fluorescence enhancement (140-fold) at 579 nm (Φ = 0.12). ZP1 is highly selective with Zn 2+ , among other metal ions including Cd 2+ , with a binding constant ( K a ) of 7.4 × 10 3 M −1 and a detection limit of 1 μM (65 ppb). Similar rhodamine derivatives with a shorter linker or with a single triazolyl group cannot function as a Zn 2+ chemosensor. ZP1 is membrane-permeable and could react with intracellular Zn 2+ in cultured HeLa cells. [ABSTRACT FROM AUTHOR]

A new fluorescent sensor 6-(2,3-dihydroxyphenyl)-5,6-dihydrobenzoimidazo[1,2-c] quinazoline (H 2 L) and the Zn(II) complex [Zn 2 L 1 2 ]∙C 2 H 5 OH (H 2 L 1 = 3-{[2-(1 H -benzoimidazol-2-yl)-phenylimino]-methyl}-benzene-1,2-diol) ( 1 ) were synthesized and characterized by single-crystal X-ray diffraction. H 2 L can be used to recognize Cu 2+ in aqueous media as an on–off fluorescent sensor, forming the Cu(II) Schiff-base complex (CuL 1 ). Furthermore, CuL 1 can serve as an off–on fluorescent sensor to detect histidine (His) via the ligand displacement approach. The sequential detection of Cu(II) and histidine shows on–off–on phenomenon. The crystal structure of the dinuclear Zn(II) complex indicates that the coordination of H 2 L with Zn(II) promotes C N bond breakage, resulting in the quinazoline ring-opening of H 2 L to form the Zn(II) Schiff-base complex ( 1 ). The experimental results proved that H + can also assist the ring-opening of H 2 L to form a Schiff base, H 2 L 1 . H 2 L is stable in neutral and weak basic solutions. This is further confirmed by the theoretical calculations. The cell imaging studies indicated that H 2 L and CuL 1 can be used to detect the intracellular Cu 2+ ion and His under physiological conditions, respectively. CuL 1 can also be used to determine His in urine. [ABSTRACT FROM AUTHOR]

The synthesis and evaluation of new quinoline based fluorescent chemosensor L1 for the detection of Zn 2+ in THF/H 2 O. The absorption and fluorescent spectra change was observed upon addition of Zn 2+ indicate that L1 is highly selective for Zn 2+ over other metal ions. The probe displayed an apparent color change while addition of Zn 2+ , which could be observed by the naked eye under a UV lamp. The experimental results have been verified with DFT and TDDFT calculation. In vitro sensitivity to Zn 2+ was demonstrated in Hela cells with the use of fluorescence confocal microscopy. [ABSTRACT FROM AUTHOR]

In this work, a simple, green and cost-effective fluorescence based analytical procedure using water soluble carbon nanoparticles (CNPs) is described for selective and sensitive detection of Iron (III) (i.e. ferric (Fe 3+ )) ions in water. The CNPs were synthesized by acid treatment of naturally occurring d -glucose followed by heating at 80 °C. The fluorescence intensity of the CNPs (excited at 360 nm) was found to decrease with the increase in concentration of Fe 3+ ions. The fluorescence lifetime of CNPs remained unchanged with increasing Fe 3+ concentration, suggesting the quenching to be static. The zeta potential which was negative for CNPs became positive on addition of Fe 3+ , thus indicating the adsorption of Fe 3+ on CNPs surface. The sensing of Fe 3+ by CNPs was also observed in-vivo using DLD cells. The limit of quantification and limit of detection of Fe 3+ ions were found to be 18 ppm and as 56.0 ppb, respectively. Validation of the proposed fluorescence quenching based technique was achieved by comparing with Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). [ABSTRACT FROM AUTHOR]

A new versatile ‘dual’ chemosensor 1 has been synthesized for Zn 2+ and Co 2+ . The sensor 1 comprises of quinoline as a fluorophore and N 1 , N 1 -dimethylethane-1,2-diamine as a water-soluble functional group. Sensor 1 showed a remarkable fluorescence enhancement in the presence of Zn 2+ in aqueous solution. The sensor 1 also acted as a colorimetric sensor for Co 2+ by changing its color from colorless to yellow. Importantly, the chemosensor 1 could be used to quantify Zn 2+ and Co 2+ in water samples and to image and quantify Zn 2+ in living cells. Moreover, the sensing mechanisms of 1 for Zn 2+ and Co 2+ were supported by theoretical calculations. Therefore, this sensor has the ability to be a practical system for monitoring Zn 2+ and Co 2+ concentrations in biological systems and aqueous samples. [ABSTRACT FROM AUTHOR]

A rhodamine derivative ( 1 ) is developed as a fluorescent chemosensor for trivalent chromium ions (Cr 3+ ). It exhibits a highly sensitive “turn-on” fluorescent response toward Cr 3+ with a 55-fold fluorescence intensity enhancement under 2 equiv. of Cr 3+ added. The chemosensor can be applied to the quantification of Cr 3+ with a linear range covering from 5.0 × 10 −7 to 2.0 × 10 −5 M and a detection limit of 1.7 × 10 −7 M. Most importantly, the fluorescence changes of the chemosensor are remarkably specific for Cr 3+ in the presence of other metal ions, which meet the selective requirements for practical application. Moreover, the response behavior of 1 toward Cr 3+ is pH independent in neutral condition (pH 6.0–8.0). The response of the chemosensor is fast (less than 2 min) and the chemosensor is chemically reversible. Furthermore, the ring-opening mechanism of the rhodamine spirolactam induced by Cr 3+ and the 1:1 stoichiometric structure between 1 and Cr 3+ were supported by Job's plot, NMR, MS and DFT theoretical calculations. In addition, the proposed chemosensor has been used to detect Cr 3+ in real water samples and image Cr 3+ in living cells with satisfying results. [ABSTRACT FROM AUTHOR]

Novel fluorescent nitrogen and sulfur co-doped carbon dots (N,S,C-dots) were synthesized by hydrothermal treatment of garlic. It was confirmed that the prepared fluorescent nanodots were doped with nitrogen and sulfur in the format of pyridinic-N, pyrrolic-N and thiophene-S. The N,S,C-dots displayed strong fluorescence with quantum yield of 13%, and the fluorescence can be efficiently quenched by Fe 3+ . Based on the results, Fe 3+ sensor was successfully developed and utilized to detect Fe 3+ in environmental waters with excellent sensitivity and repeatability. Eventually, the carbon dots were applied for cell imaging, demonstrating their potential toward diverse applications. [ABSTRACT FROM AUTHOR]

Herein, a simple and green method was developed for the construction of water soluble fluorescent gold nanoclusters (Au NCs) with the assistance of l -carnosine as both a protecting ligand and a weak reducing agent. The as-prepared Au NCs, with the smaller size (2.31 nm) and longer fluorescence lifetime (7.48 ns), exhibited bright blue photoluminescence under UV light (365 nm) with a quantum yield of 3.4%, excellent stability, and low toxicity for cancer HeLa cell imaging. [ABSTRACT FROM AUTHOR]

A new turn-on fluorescent quinolone tetrazole based chemosensor (QT-1) is designed and synthesized which shows high sensitivity and selectivity for Zn 2+ ions in aqueous acetonitrile solution. QT-1 probe easily distinguishes Zn 2+ ions from Cd 2+ ions. Job's plot analysis suggested that the binding of QT-1 and Zn 2+ ions is probably a 1:1 stoichiometry. Thus QT-1 can be employed for fluorescent imaging of Zn 2+ ions in living cells. [ABSTRACT FROM AUTHOR]

A red-emitting (above 600 nm) fluorescent probe based on 3-hydroxyflavone has been developed for the detection of hydrogen sulfide with high sensitivity, good selectivity and a large Stokes shift (162 nm). When the probe was treated with hydrogen sulfide, a remarkable fluorescence enhancement (112-fold) was obtained. Application of this probe was successfully demonstrated by imaging intracellular hydrogen sulfide in living RAW264.7 cells. [ABSTRACT FROM AUTHOR]

BODIPY functionalized Au nanoparticles (PyBDP-AuNPs) have been developed for detecting cysteine. Gold nanoparticles were prepared by reducing HAuCl 4 with sodium citrate, using PyBDP as the capping agent. Upon addition of cysteine, PyBDP molecules are liberated from the AuNP surface through ligand-exchange displacement based on the strong affinity of Au with the thiol group and result in green fluorescence from PyBDP molecules. This cysteine-induced displacement of PyBDP-AuNPs was monitored by fluorescent spectroscopy with a detection limit of 1.2 μM. Optimal detection of cysteine was achieved over a pH range from 5 to 12. In addition, PyBDP-AuNPs can be used as a fluorescent probe for detecting cysteine in living cells. [ABSTRACT FROM AUTHOR]

A Schiff-base compound, 1-(2-hydroxy-5-methylphenylimino)naphthalen-2-ol ( 1b ), has been synthesized and characterized using elemental analysis and different spectroscopic methods. It behaves as highly selective fluorescent chemosensor for Al(III) in 10 mM HEPES buffer in water:methanol (1:9, v/v) (pH 7.2). Fluorescence intensity at 552 nm (excitation at 450 nm) of 1b increases about 200 fold upon addition of 2 equiv. of Al 3+ ion. Quantum yield of 1b increases about 10.8 times upon complex formation with Al 3+ . 1b forms complex with Al 3+ in 1:1 ratio as supported by Job's plot analysis and mass spectroscopic measurement. Chelation enhanced fluorescence of 1b in the presence of aluminum(III) ion is evidenced from large decrease in nonradiative rate constant and high binding constant value. The probe molecule has been applied in living cell imaging study. [ABSTRACT FROM AUTHOR]

A new simple “off–on fluorescence type” chemosensor 1 (2-( N -(2-hydroxyethyl)- N -((pyridin-2-yl)methyl)amino)- N -(quinolin-8-yl)acetamide) has been synthesized for Zn 2+ . The sensor 1 comprises of the quinoline as fluorophore and the 2-((pyridin-2-yl)methylamino)ethanol as both binding site and water-soluble functional group. 1 showed a remarkable fluorescence enhancement in the presence of Zn 2+ in aqueous solution, which was reversible with the addition of ethylenediaminetetraacetic acid (EDTA). The detection limit (0.02 μM) of 1 for Zn 2+ is far lower than World Health Organization guideline (76 μM) in drinking water. Importantly, the chemosensor 1 could be used to detect and quantify Zn 2+ in living cells and water samples. Moreover, the sensing mechanism was supported by theoretical calculations. Therefore, this sensor has the ability to be a practical system for monitoring Zn 2+ concentrations in biological and aqueous samples. [ABSTRACT FROM AUTHOR]

Hypoxia is a trait that widely exists in 90% of solid tumors. Under hypoxic conditions, biological reductase enzymes in tumors will be overexpressed (e.g., azoreductase). This feature is often used to design fluorescence probes to recognize hypoxic cells from normoxic cells. The presently reported fluorescence probes are mostly designed by covalent bonds, which requires tedious synthesis. In this study, a fluorescence nanoprobe was prepared by encapsulating azobenzene into assemblies of polymeric amphiphiles bearing fluorophores (denoted by PAF). The nanoprobes without azobenzene are strongly emitted in aqueous solution, and the emission was effectively quenched when azobenzene was included in the nanoprobes. The nanoprobes with azobenzene showed quite different emission intensities when cultured in hypoxic and normoxic cells, leading to fluorescence quantum yields (QYs) of 18.0% vs. 1.5%, respectively. Here, we demonstrated a facile method to prepare an azoreductase-responsive fluorescent nanoprobe that can selectively light up malignant cells from benign cells. [Display omitted] • A turn-on fluorescence probe is designed by supramolecular assembly. • The probe has good light stability, high selectivity and excellent biocompatibility. • The probe was successfully applied to selectively light up malignant cells. [ABSTRACT FROM AUTHOR]

Caspase-3 is considered to be a key regulator of cell apoptosis. Simultaneous activation and detection of caspase-3 in living cells is therefore highly important for precise cancer therapy and therapeutic efficacy evaluation but it is still a key challenge. Herein, a novel and simple multifunctional peptide-tailored mesoporous carbon nanospheres (MCN) has been developed for simultaneous cancer photothermal therapy (PTT) and real-time imaging of caspase-3 induced cell apoptosis. The nanoprobe was facilely prepared by modifying fluorescein isothiocyanate (FITC)-tagged peptide specific to caspase-3 on the surface of MCN. The signal switch relies on the unique quenching effect of MCN on the fluorescently labeled peptide, cleavage of the peptide by activated caspase-3 will result in a significant fluorescence lighting-up for sensitive caspase-3 analysis. The detection limit of 0.4 pg·mL−1 with a linear range from 10 pg·mL−1 to 1 ng·mL−1 was achieved. Owing to the intrinsic properties of MCN, the nanoprobe not only can be served as photothermal transducer to activate caspase-3, but also can simultaneously real-time monitoring caspase-3 activity in living cells with high specificity. This work demonstrates a smart molecular imaging strategy for cell apoptosis, which also provides a potential new platform for apoptosis-related diagnosis and precise cancer therapeutic applications. • A simple and novel multifunctional fluorescent nanoprobe was developed. • Simultaneous activation and detection of caspase-3 was achieved by the MCN-based fluorescent nanoprobe. • Real-time in situ imaging and tracking caspase-3 dynamics in living cells was realized. [ABSTRACT FROM AUTHOR]

More evidence supports that endoplasmic reticulums stress (ER stress) has close relationship with many disease, including Alzheimer's disease, and such diseases are often closely related to senescence. Both ER stress and senescence involve disorder of redox regulation and may further cause ClO- accumulation. It is of great importance to develop a tool to visualize ralated organelles to investigate the role of ClO- during ER stress or senescence. In this work, a novel dual-targetable ClO- probe RT-ER was designed, and the probe could image endoplasmic reticulums and lysosome by sequence under stimulation of ClO-. RT-ER worked in a ratiometric manner and was extremely sensitive to ClO-(~ 484 folds enchancement within 10 s after the stimulation of ClO-). RT-ER showed great biocompatibility and was further applied in living cells imaging. We demonstrated that RT-ER enables both exogenous and endogenous ClO- imaging. Compared with the commercial dye Lysosome-Tracker Deep Red, RT-ER showed better photobleaching resistance. We successfully used RT-ER to track the interaction between endoplasmic reticulum and lysosome after ClO- accumulation. More importantly, with the help of RT-ER, we further revealed the level of ClO- change during ER stress and senescence, which will facilitate the functional study of ClO- −disease contacts. [Display omitted] • The probe could image ERs and lysososme in two channels by sequence with stimulation of ClO-. • The intereactions between lysosome and ER can be long-term tracked by the probe when ClO- continue to accumulate in cells. • The fluctuation of ClO- during ERs stress and senescence can be monitored by the probe. [ABSTRACT FROM AUTHOR]

A phenothiazine–aminothiourea-based open chemosensor ( P1 ) has been designed and synthesized, which exhibits high selectivity toward Hg 2+ by forming a 1:1 complex. In its Hg 2+ ensemble, it is reported as a highly sensitive and selective probe for the detection of iodide based on the displacement approach in aqueous solution. The addition of iodide to a solution of phenothiazine–aminothiourea–Hg 2+ ensemble resulted in a rapid and remarkable fluorescence off–on (emission at 565 nm). The practical use of an ‘ensemble’ was demonstrated by its application to the detection of iodide in the living cells. [ABSTRACT FROM AUTHOR]

A boron dipyrromethene (BODIPY) derivative (BODTe) with an NTe 2 chelating motif exhibits high selectivity for Hg 2+ detection. Significant fluorescence enhancement was observed with the chemosensor BODTe in the presence of Hg 2+ . However, the metal ions Ag + , Al 3+ , Ca 2+ , Cd 2+ , Co 2+ , Cu 2+ ,Cr 3+ , Fe 2+ , Fe 3+ , Hg 2+ , Mg 2+ , Mn 2+ , Ni 2+ , Pb 2+ , and Zn 2+ produced only minor changes in the fluorescence values of the system. The association constant ( K a ) of Hg 2+ binding for the chemosensor BODTe was found to be 3.84 × 10 3 M −1 , with a detection limit of 19.2 μM. The maximum fluorescence enhancement caused by Hg 2+ binding in the chemosensor BODTe was observed over the pH range of 4.0–10.0. Confocal fluorescence microscopy imaging using RAW 264.7 cells showed that BODTe can be used as an effective fluorescent probe for detecting Hg 2+ in living cells. [ABSTRACT FROM AUTHOR]

We report a green and facile strategy for fabrication of dual-emission carbon nanodots (CDs), and demonstrate their applications in ratiometric sensing and cellular imaging. Dual-emission CDs have been prepared by pyrolysis and microwave treatment of naked oats, providing a novel way for the production of dual luminance CDs without the request of tedious synthetic methodology or the use of toxic/expensive solvents and starting materials. Their intriguing dual fluorescence behavior is observed when the excitation wavelength is between 250 and 310 nm. The well-resolved dual emission bands manifest excitation and temperature dependence. The obtained CDs were applied as a ratiometric fluorescent sensing platform for precise and quantitative detection of Al 3+ ions and pH values, and as optical nanoprobes for cellular imaging. [ABSTRACT FROM AUTHOR]

A highly sensitive and selective quinoline based reversible chemosensor (HL) for the efficient detection of Zn 2+ has been developed. The synthesized chemosensor HL is highly efficient in detecting Zn 2+ over other metal ions commonly obtained in physiological and environmental samples. HL shows fluorescence ‘turn-on’ response with 53 fold enhancement of emission intensity in presence of Zn 2+ . The limit of detection is 5.0 × 10 −9 M. HL is efficient in detecting Zn 2+ intracellularly and also exhibits an INHIBIT logic gate with Zn 2+ and EDTA as chemical inputs by monitoring the emission mode. Electronic structure and sensing mechanism have been interpreted by DFT and TDDFT calculations. [ABSTRACT FROM AUTHOR]

A chemosensor 3-[(2-hydroxybenzylidene)-amino]-1H-pyridin-2-one (HL) for multi-ions was synthesized and characterized by single-crystal X-ray diffraction. HL is a turn-on fluorescence chemosensor for Al 3+ , F − , and CN − ions in DMSO. F − and CN − anions could be further distinguished by the ratiometric absorption spectrometry method. Job plot and 1 H NMR data showed that the binding stoichiometries of HL with Al 3+ , F − , or CN − all were 1:1. Further observations of 1 H NMR titration and ESI-MS showed that the possible fluorescent species of Al 3+ with HL was [AlL(OH)(DMSO) 2 ] + in DMSO. The spectroscopic observations of the Al(III) complex showed that the two oxygen atoms and one imine nitrogen atom of HL were coordinated to the Al(III) ion. While the crystal structure of the Ni(II)-L complex confirmed the tridentate coordination mode of HL in the complexes. The experimental results revealed that HL and F − ion formed hydrogen bond in DMSO, while CN − attacked the carbon atom at –C N of HL to undergo a nucleophilic addition. The theoretical calculations confirmed that HL showed very weak fluorescence because of the excited-state intramolecular proton transfer (ESIPT). The turn-on sensing of HL to Al 3+ , F − , and CN − ions arose from the inhibition of ESIPT. MTT tests showed that HL was low toxic to cells. Also, HL could probe intracellular Al 3+ and F − ions by bioimaging. [ABSTRACT FROM AUTHOR]

Two Schiff base derivatives based on diaminomaleonitrile were synthesized and characterized. Both of the two compounds displayed a highly selective UV and off-on type fluorescent response to Cu 2+ in acetonitrile solution. The mixtures of Cu 2+ with 1 or 2 showed great potential application in bioimaging. Two different polymorphs of compound 1 were obtained from ethanol and ethyl acetate, respectively, which exhibit obvious differences in the wavelength and intensity of the fluorescence emission. This interesting phenomenon may originate from the tightness of packing and π–π interactions in the stacking structure. Compound 2 was aggregation-enhanced emission (AEE)-active in tetrahydrofuran (THF)/water mixtures. Moreover, compound 2 in a solid amorphous state was collected though special methods, which showed completely different fluorescence compared with that of the crystal due to the irregular molecular aggregation pattern. [ABSTRACT FROM AUTHOR]

A novel 4-amino-1,8-naphthalimide-based fluorescent Cd 2+ sensor with phenyliminoethoxy-ethoxyoxyacetic acid as receptor, was developed and applied successfully to image Cd 2+ in living cells. It demonstrates high selectivity and sensitivity for sensing Cd 2+ with about 24-fold enhancement in aqueous solution. Particularly, it is high selectivity against Zn 2+ . [ABSTRACT FROM AUTHOR]

Two new quinoline hydrazones were synthesized, characterized and investigated as reversible ratiometric fluorescence pH sensors in the acidic pH region. The sensors were designed by the formation of simple donor-acceptor couple of quinoline aldehyde and phenyl hydrazine where protonation of quinoline-N triggered the pH sensing. No significant interference on emission behavior was observed in the presence of various metal ions. The sensors were used to visualize HeLa cells both at acidic and neutral pH with different emission. The MTT assay revealed negligible toxicity for both the hydrazones. The spectral properties, especially the large Stokes shift and the geometry of the molecules at the ground and excited states had been rationalized through DFT and TDDFT studies. [ABSTRACT FROM AUTHOR]

Abstract: A new coumarin derivative (MS1) containing an imine moiety and a hydroxyl moiety exhibits an enhanced fluorescence in the presence of Hg2+ ions. Other metal ions Al3+, Ca2+, Co2+, Cr3+, Cu2+, Fe2+, Fe3+, Hg2+, K+, Mg2+, Mn2+, Ni2+, Pb2+, and Zn2+ produced only minor changes in the fluorescence values of MS1. The binding ratio of MS1–Hg2+ complexes was determined from the Job plot to be 1:1. The binding constant (K a) of Hg2+ binding to MS1 was found to be 6.85×103 M−1. The maximum fluorescence enhancement caused by Hg2+ binding to MS1 was observed in the pH range of 6.5–9.0. Confocal fluorescence microscopy imaging using RAW 264.7 cells showed that MS1 could be used as an effective fluorescent probe for detecting Hg2+ in living cells. [Copyright &y& Elsevier]

• A spatial confinement fluorescence RNA with stable structure and strong signal output was developed for cell imaging. • Benefiting from the abundant DFHBI binding sites of the spatial confinement probe, the strategy showed a high sensitivity. • The superior bio-stability was attributed to the large steric hindrance of compact network frameworks and DNA fixation. • The proposed method can evaluate the telomerase RNA in HeLa, HepG2 and HL-7702 cell. A critical challenge for cell imaging is that the reduced stability and intensity of signal probe suffering from the complex cellular environment. Here, we present a spatial confinement fluorescence RNA with stable structure and strong signal output for cell imaging, which was generated in situ by a cascaded rolling circle transcription (RCT) and DNA fixation. In this assay, two functional padlock probes (P 1 , P 2), one hairpin probe (HP) and ssDNA were designed as the building blocks, human telomerase RNA (hTR) was chosen as a model. Under the action of hTR, P 1 was circularized and initiated the first RCT, producing RNA nanowires for hybridization with HP. The unfolded HP subsequently hybridized with P 2 to initiate the second RCT reaction, producing large amounts of spinach RNA aptamer strung to long RNAs. Cycles of the above RCT reactions were repeated in both vertical directions resulting in a high confinement spinach RNA aptamer in a 2D matrix. Finally, spinach RNA aptamer was hybridized with ssDNA and displayed strong fluorescence upon binding the non-fluorescent fluorophore (DFHBI), thus realizing in situ amplified label-free imaging. In our system, the proposed spinach RNA matrix carries amounts of signal reporting sites in a limited space, which facilitates the transporting and binding of DFHBI, thereby providing a high-contrast signal response and a low detection limit (LOD). Importantly, the fluorescence intensity in serum exhibited no significant decrease after 4 h (97.7 %). Its superior biological stability is attributed to the large steric hindrances of the tight frame that prevent intracellular degradation, and the DNA fixation strategy that solidifying the structure of spinach RNA while preventing DFHBI leakage. Moreover, the expression of hTR in different cells (A549, HepG2 and HL-7702) were also performed successfully, providing a powerful platform for assaying biomarkers in cells. [ABSTRACT FROM AUTHOR]

A novel fluorescent "turn on" nanoprobe for caspase-1 activity assay has been constructed based on conjugation of AuNRs and RCDs through a short peptide. This fabrication and detection strategy provides high sensitivity, specificity, and stability in cell extract sample detection and in-situ living cell imaging. [Display omitted] • A novel fluorescence nanoprobe were constructed for caspase-1 activity analysis. • The facet-controlled AuNRs improve fluorescence surface energy transfer efficiency. • Prior treated the AuNRs with PEG-SH enhanced the stability of the nanoprobe. • The nanoprobe determine caspase-1 activity sensitively with a LOD of 1.76 ng mL-1. • The fluorescence nanoprobe can probe the intracellular caspase-1 activity levels. The development of sensitive and convenient strategies for monitoring intracellular caspase-1 activity is of great significance. Herein, a novel fluorescence nanoprobe for caspase-1 activity determination was constructed based on surface energy transfer (SET) between red-emissive carbon dots (RCDs) as a donor, and Au nanorods (AuNRs) as an acceptor. The donor/acceptor pair were covalently bridged with a peptide containing a caspase-1 cleavage site (YVAD) at middle. The stability and dispersivity of the AuNR-Pep-RCD nanoprobe was realized/enhanced by pretreating the AuNRs with PEG-SH. Active caspase-1 cleaves the YVAD site, releasing RCDs and recovering the fluorescence. Synergic effect of the red-emission, sensitive and selective cleavage, and excellent SET efficiency contribute to the nanoprobe with high sensitivity and selectivity, especially in biological samples. More importantly, the nanoprobe can be uptaken by living cells, capable of in-situ intracellular caspase-1 activity imaging. The fluorescence recovery is linearly correlated with caspase-1 activity in the range of 5‒300 ng·mL−1 (2.5 × 10−5‒1.3 × 10−3 U·mL−1), with a limit of detection of 1.76 ng·mL−1 (8.8 × 10-6 U·mL−1). In particular, the fluorescence nanoprobe can accurately detect caspase-1 activity in cells extract, and sensitively probe the caspase-1 activation treatment and inhibition treatment for the intracellular caspase-1 activity levels. [ABSTRACT FROM AUTHOR]

[Display omitted] • The tumor-targeting and biothiol activatable fluorescent probe Biotin-Yellow was developed. • Biotin-Yellow is non-toxic, it can effectively recognize and discriminate cancer cells from embryonic fibroblasts cells. • Biotin-Yellow has unprecedented turn-on near-infrared fluorescence and colorimetric properties. • Biotin-Yellow can be employed for real-time bioimaging tracking of biothiols in cancer cells. • The efficacy and biothiol responsiveness of Biotin-Yellow was validated in vivo in zebrafish and mice. A dicyanomethylene-4H-pyran based tumor-targeting and biothiol activatable fluorescent and colorimetric probe, named Biotin-Yellow, has been developed with unprecedented turn-on near-infrared fluorescence properties. Biotin-Yellow is non-toxic and can effectively recognize and discriminate human lung adenocarcinoma cells and urothelial (bladder) carcinoma cells from embryonic kidney cells and embryonic fibroblasts. Biotin-Yellow can also be employed for real-time bioimaging tracking of upregulated biothiol activity in cancer cells. The efficacy and biothiol responsiveness of Biotin-Yellow was further validated in vivo in zebrafish and mice xenografts. [ABSTRACT FROM AUTHOR]

• A novel fluorescent probe was synthesized for the detection of ONOO− by conjugating dicyano-vinyl with benzopyran-chromone. • The probe shows specifically selectivity over other biologically relevant ROS/RNS/RSS. • The sensing mechanism is the cleavage of the carbon-carbon double bond by the nucleophilicity and oxidation of peroxynitrite. • The probe has a certain mitochondrial targeting and localization effect. • BC-PN-2 can accurately identify ONOO− in mitochondria by imaging of exogenous ONOO− in HepG2 cells. A novel fluorescent probe (BC-PN-2) for the detection of ONOO− was synthesized by conjugating dicyano-vinyl with benzopyran-chromone. The dicyano-vinyl group can be destructed by ONOO− to generate an aldehyde group resulting in strong fluorescence. Compared with the general fluorescence probes, a novel reactive site to detect ONOO− in mitochondria is used in this probe and the results show short response time, high sensitivity and excellent selectivity toward ONOO− among reactive oxygen species (ROS) and reactive nitrogen species (RNS) in PBS. Subsequent fluorescence imaging shows the high membrane permeability, a certain mitochondrial targeting and localization effect of the probe. In addition, the product BC-aldehyde cannot permeate through the membrane. Meanwhile, BC-PN-2 can accurately identify ONOO− in mitochondria by imaging of exogenous ONOO− in HepG2 cells and prove detected ONOO− are from mitochondria. [ABSTRACT FROM AUTHOR]

• A reaction-based ratiometric fluorescent nanosensor for H 2 S is established with RhB/UiO-66-N 3 MOF. • The size of RhB/UiO-66-N 3 can be easily tuned to nanoscale for direct in vivo evaluation. • RhB/UiO-66-N 3 endows good stability, selectivity and reliability for H 2 S analysis under physiological conditions. • Exogenous and endogenous H 2 S in live cells has been successfully targeted and imaged. As a vital signaling molecules, hydrogen sulfide (H 2 S) with abnormal concentrations is correlated with many diseases. Therefore, development of novel assays for quantitative and selective detection of H 2 S is important. Herein, we synthesized a host-guest metal-organic framework (MOF), i.e., RhB/UiO-66-N 3 (here, RhB means rhodamine B) by a mildly and simply way, as reaction-based ratiometric fluorescent nanosensor for selective detection and intracellular imaging of H 2 S. In the presence of H 2 S, the RhB/UiO-66-N 3 exhibits dual emissions at 425 nm and 575 nm under irradiation of single excitation wavelength. The blue fluorescence at 425 nm (F 425) is attributed to the H 2 S-mediated biorthogonal reduction of azide to amine, and the red fluorescence at 575 nm (F 575) originating from RhB is served as an internal reference. With increasing concentrations of H 2 S, the intensity of blue fluorescence increases while the intensity of red fluorescence has no obvious change. With F 425 /F 575 as readout, turn-on and ratiometric fluorescence detection of H 2 S was achieved with good selectivity and sensitivity. Interestingly, RhB/UiO-66-N 3 can be tuned from microscale to nanoscale sizes, and endows high stability under physiological conditions. The exogenous and endogenous H 2 S in live cells has been further targeted and imaged, demonstrating its considerable potential for extensive applications. [ABSTRACT FROM AUTHOR]

• A two-photon fluorescent probe is developed for detecting cyclooxygenase-2 (COX-2) activity in human colon tissues. • The probe is based on a novel two-photon fluorophore possessing significant two-photon brightness (160 GM). • The probe can clearly distinguish the differential COX-2 level between human cancer and normal colorectal tissues. Cyclooxygenase-2 is overexpressed in all stages of cancers and thus serves as an attractive biomarker for early cancer diagnosis. In this study, we report a two-photon probe (SCX) for cyclooxygenase-2 which can reflect the intracellular enzyme level and distinguish between cancerous and normal tissue in colorectal cancer patients. SCX is based on a novel two-photon fluorophore (PBT) possessing phenanthrene donor and benzothiazole acceptor, and indomethacin as a COX-2 targeting unit. The in vitro and cell imaging studies revealed that SCX could distinguish the COX-2 expression levels in cancerous and normal cells. Furthermore, for the first time, normal and cancerous tissues could clearly be distinguished in human biopsy samples by using a COX-2 responsible two-photon probe. [ABSTRACT FROM AUTHOR]

• A new method has been proposed for monitoring PNK activity in vitro , natural compound screening and intracellular imaging. • NS17 isolated from Kadsura heteroclita screened as PNK inhibitor, which effect confirmed in vitro and in cell level. • NS17 can scavenge intracellular ROS, inhibit inflammatory cells proliferation and down-regulate COX-2 expression. Polynucleotide kinase (PNK) is critical for nucleic acid metabolism, as its overexpression can increase ROS production and activate the inflammation pathway, leading to chronic inflammation. In this study, we proposed a new fluorescence method for monitoring PNK in vitro , natural compounds screening and intracellular imaging. Quantitative detection depicted that the limit of detection (LOD) of PNK is 0.0021 U/mL in the linear range of 0.01∼10 U/mL. Methodological evaluation showed that both of the selectivity and the inhibitory effect of ADP and EDTA on PNK activity with satisfactory results. Fluorescence imaging of inflammatory cells demonstrated the reliability of platform for capturing PNK change in situ regulated by inhibitor of natural compound NS17 isolated from Kadsura heterolita. Mechanism study showed that the inhibitor NS17 can reduce inflammation by scavenging intracellular ROS, killing inflammatory cells and down-regulating COX-2 expression, the processes of which are related with PNK activity. In summary, above results suggest that this new platform could monitor PNK activity in situ and screen inflammation inhibitors targeted on PNK. [ABSTRACT FROM AUTHOR]

• We have developed a sensor that detects N 2 H 4 in 99 % water environment referening drug molecular design methods. • A reasonable strategy for the construction of water-soluble fluorescent sensors was developed. • The measurement scope of this sensor is 0.28∼120μM, LOD = 1.22ppb. • Long stokes shift (91nm) can effectively eliminate the inherent bioluminescence interference in short wavelengths. Hydrazine is a serious hazard for humans; therefore, the detection of N 2 H 4 is extremely important. In recent years, fluorescence sensing, which is a simple and efficient method, has attracted immense attention. Although sensors for hydrazine have been reported, only a few have successfully worked in almost pure water media, Therefore, organic cosolvents are required, however, they are known to interfere with the analysis of the real sample. Furthermore, a few currently known hydrazine sensors have emission wavelengths smaller than the size of the organism itself, thereby making it difficult to eliminate the inherent bioluminescence interference at short wavelengths. In order to solve these problems, we have developed a new type of water-soluble(LogP (Oct/buff) = 1.68, LogD7.4=-1.97), fluorescent, colorimetric sensor. This sensor is based on the ICT mechanism to specifically detect N 2 H 4 in colorimetric and proportional modes (measurement scope is 0.28–120 μM, LOD = 1.22 ppb). In addition, it was successfully used to image A549 cells and detect hydrazine in river water samples and water vapor. [ABSTRACT FROM AUTHOR]

• The DNAzyme-rGO coupled fluorescence assay achieved ultra-sensitive detection of T4PNK. • This method shows great potential in inhibitor analysis, enzyme kinetic studies, and natural drug screening of T4PNK. • This is the first study to monitor T4 PNK activity in in living cells. • Activation of T4PNK by natural compounds was verified by imaging in HepG2 cells. Phosphorylation of DNA caused by T4 PNK is an important regulatory process that associated with many cellular events and diseases. Here, we proposed a DNAzyme-rGO coupled fluoresence method for T4 PNK detection. Under the optimal conditions, the approach exhibits high sensitivity with a detection limit of 0.001 U/mL, and there was a reliable linear relationship between fluorescence intensity and T4 PNK concentration in the range of T4 PNK from 0.001 U/mL ∼ 5 U/mL. Then, this method was used for kinetic analysis and effectors screening from natural compounds. Finally, the method was applied to monitor activity of T4 PNK in vitro and intracellular imaging of T4 PNK. In summary, this sensitive and specific sensing platform for T4 PNK assay can be hopefully used for clinical diagnosis, prognosis evaluation and targeted drug screening. [ABSTRACT FROM AUTHOR]

• A robust strategy for probe design with dual-quenching groups in one probe. • The strategy has been applied for designing HOCl fluorescent probe successfully. • The strategy can both enhance the probe's sensitivity and selectivity significantly. • The detection limit for HOCl is as low as 3.5 nM. • Two-photon probe has been used to detect HOCl in living cells and kidney tissues. We report herein fluorescent probes equipped with dual-quenching groups exhibiting superior sensitivity than probes with mono-quenching groups. Importantly, with this strategy, the probe with dual-quenching groups react with HOCl through two distinct reaction mechanisms, which reduce the plausible side reactions with other competing analytes and enhance the probe's selectivity. As a proof-of-concept study, we designed and synthesized a probe with dual-quenching groups DQ-HOCl to detect HOCl, which is one of the most important ROS and linked with a number of diseases. In addition, two control probes with mono-quenching groups, MQ-HOCl-1 and MQ-HOCl-2 , were also synthesized for comparison purpose. Fluorescent assays demonstrated that DQ-HOCl indeed shows ultra-high sensitivity and selectivity compared with probes with mono-quenching groups. Furthermore, the probe has been successfully utilized to imaging exogenous/endogenous HOCl in living cells. Moreover, DQ-HOCl was applied to visualize HOCl in kidney tissues from rat due to the increased penetration depth and lower tissue autofluorescence from the nature of two-photon probes. [ABSTRACT FROM AUTHOR]

• A fluorescence "turn-on" method was developed for MUC1 detection and targeted cancer imaging. • The specific interaction of MUC1 with its aptamer led to the fluorescence swithching. • Successful detecion of MUC1 in aqueous media was achieved with a detection limit of 0.8 nM. • The method allowed to map the spatial expression of MUC1 in cancer cells with excellent sensitivity. Mucin 1 (MUC1) is an important biomarker that has been shown to participate in the metastasis and invasion of various types of cancers. Simple yet sensitive methods for the detection of MUC1 in liquid and in situ imaging of MUC1 at cellular level are crucial for early diagnosis of cancers as well as monitoring their progression. Herein, a polydiacetylene (PDA) liposome-based sensing system functionalized with Cy3-labeled MUC1 binding aptamer (Cy3-Apt) was developed as a fluorescence "turn-on" nanosensor for the detection of MUC1. In the sensing system, the fluorescence of Cy3-Apt could be directly quenched due to the energy transfer between the fluorogen and PDA conjugated backbone. In the presence of MUC1, the recognition of MUC1 with its aptamer induces the structure switching of both PDA liposomes and the aptamer, recovering the red fluorescence. Sensitive and selective analysis of MUC1 in aqueous media could be achieved with a limit of detection around 0.8 nM. The feasibility of the nanosensor was further demonstrated by mapping the spatial expression of MUC1 in cancer cells with excellent sensitivity. [ABSTRACT FROM AUTHOR]

• We developed dual-functioning IQ-LVs as red-emissive lysosomal viscosity sensors and inhibitors of autophagic flux. • The absence of the methoxyphenyl E ring in IQ-LVs enhanced the viscosity sensitivity. • The pH sensitivity was minimized by tuning R 2. • The mono-protonated form (A'-IQH+) emits red fluorescence in a viscosity-sensitive manner. Current fluorescent probes for lysosomes have practical limits due to their pH sensitivity, which makes them unsuitable for long-term tracking of lysosomes in live cell imaging. In addition, viscosity probes are also responsive to polarity, which imposes considerable challenges in cellular imaging. Here, we report IQ-LV s, which can serve as viscosity sensors at the lysosomal pH. In contrast to the majority of current molecular rotors that exhibit blue and green emission, IQ-LV s showed red-shifted emission (∼95 nm) upon increasing the viscosity at pH 4.5. Among the synthesized viscosity sensors, IQ-LV57 and IQ-LV70 lacking an aromatic ring at R 1 displayed 15-fold and 116-fold enhancement of red-shifted emission, respectively, upon changes in viscosity. They showed negligible polarity dependency, while the pH sensitivity was minimized by tuning R 2 as we envisioned. Our 1D 1H-NMR titrations along with TCSPC analysis revealed that IQ-LV s exhibit two emissions in lysosomes, viscosity-insensitive green emission (+HA'-IQH+) and viscosity-sensitive red-shifted emission (A'-IQH+), which enabled live cell imaging for tracking lysosomes during the autophagy process. In fluorescence confocal imaging, the red emission was enhanced upon the increase in lysosomal viscosity in HeLa and MCF7 cells, and the observed emission from IQ-LV57 and IQ-LV70 had a longer duration than that of LysoTracker™ Deep Red in time-lapse images of live MCF7 cells. Furthermore, treatment of IQ-LV37 in MCF7 cells resulted in increased autophagosomes and autolysosomes during the autophagy process. Further western blot analysis revealed that IQ-LV37 and IQ-LV57 block the degradation of autophagosomes, serving as autophagy inhibitors. [ABSTRACT FROM AUTHOR]

• First fluorescent sensor for simultaneously sensing Zn2+, Cd2+ and Hg2+ was reported. • The sensor exhibited excellent red fluorescence at 500−526 nm in aqueous media. • The detection of Zn2+, Cd2+ or Hg2+ showed obvious color changes of fluorescence. • The detection limits were as low as 8.22 × 10−8 M, 2.36 × 10−7 M and 3.43 × 10−8 M. • The sensor was used in test strips and cell-imaging for sensing Zn2+, Cd2+ and Hg2+. This work report the first AIE-based fluorescence sensor that can simultaneously detect three kinds of IIB elements (Zn2+, Cd2+ and Hg2+) in aqueous media. The thiourea-bridging bis-tetraphenylethylene (Bis-TPE) was synthesized by the condensation reaction of formyltetraphenylethylene and bis-thiosemicarbazide derivative in 82 % yield. Due to the AIE effect in the aqueous medium, the long-wavelength fluorescence was observed at 500–526 nm. It displayed high selective Zn2+-sensing ability with red-to-green fluorescence change, selective Cd2+-sensing ability with red-to-yellow fluorescence change and selective Hg2+-sensing ability with fluorescence enhancement, respectively. Moreover, it could detect simultaneously Zn2+, Cd2+ and Hg2+ in the mixed solution of these three kinds of cations by the fluorescence change with the assistance of Cl− and ATP. The sensing mechanism was confirmed as 1:1 stoichiometric ratio between host and guest. The detection limits were as low as 8.22×10-8 M, 2.36×10-7 M and 3.43×10-8 M for Zn2+, Cd2+ and Hg2+, respectively. These sensing abilities were applied as test strips for detecting Zn2+, Cd2+ and Hg2+, and were used for living cell imaging, implying a high efficient and simple method for analyzing trace IIB elements (Zn2+, Cd2+ and Hg2+) simultaneously in complex environments and living bodies. [ABSTRACT FROM AUTHOR]

• Cyanine dye with benzo[e]indol and aromatic azonia unites have dual organelles target abilities. • A probe was designed for the detection of NTR in mitochondria and lysosome simultaneously. • NIR emission, fast OFF-ON response (180 s) and low detection limit (3.2 ng/mL). In this article, a benzo[ e ]indol aromatic azonia skeleton cyanine dye (3) with excellent performance was developed successfully through simple modification of an original aromatic azonia skeleton cyanine dye. Dye 3 had mitochondria/lysosome-targeting ability and its maximum emission wavelength extended to the near infrared region (655 nm). Inspired by this, probe 1a was designed, which connecting 2-bromomethyl-5-nitrofuran to the cyanine dye 3 , and was the first mitochondria and lysosome dual-targeting probe for nitroreductase (NTR) detection. In addition to exhibiting good selectivity and fast response (180 s), probe 1a also exhibited high sensitivity to NTR (the detection limit was 3.2 ng/mL). The cell imaging experiments showed probe 1a could work as a dual mitochondria/lysosome-targeting probe to detect NTR in HeLa cells. [ABSTRACT FROM AUTHOR]

The Hg(II) complex of rhodamine-nitronaphthalimide 1 can sense and discriminate both the oxidised and reduced forms of glutathione (GSSG and GSH). • The unique crystal structure of 1 shows coplanar chromophores—energy transfer processes such as FRET can readily occur. • The 1 :Hg complex gives a unique fluorescent response for both forms of the biologically relevant glutathione (GSH and GSSG). • Cellular imaging shows that 1 readily crosses cell membranes and has potential use in evaluating biochemical redox processes. Dual-fluorophore systems have attracted attention as they offer versatile photophysical properties and multiple mechanisms for sensing. Here we report that the Hg2+ complex of rhodamine-nitronaphthalimide conjugate 1 functions as a switch-on sensor for the simultaneous detection of reduced (GSH) and oxidised (GSSG) glutathione via a resonance Rayleigh scattering process, with detection limits of 4.3 μM and 11.9 μM, respectively. Hydroxide anion regenerates nitronanphthalimide 1 causing the fluorescence to "switch-off", and the system is recyclable. This photophysical behaviour towards Hg2+, GSH and HO‾ forms the basis of a molecular level INHIBIT and AND logic gate. [ABSTRACT FROM AUTHOR]

• Novel synthetic acryloyl protected GFP chromophore based H 2 S chemodosimeter. • Rapid, selective and sensitive detection of H 2 S over wide range of anions and competitive biological thiols. • Efficient to detect H 2 S in live cells such as HCT and HDF cells. • Exhibited around 290-folds fluorescence enhancement and 1000 times lower detection limit compared to reported WHO limit. Hydrogen sulphide is a gaseous neurotransmitter responsible for neuronal function and controls vast range of physiological functions. Herein, we report the synthesis and evaluation of novel Green Fluorescent Protein (GFP) chromophore analog, acryloyl-4-(p-hydroxybenzylidene)-5-imidazolidinone (AHBI) for turn-on fluorescent detection of H 2 S over wide range of anions and various biologically important competitive thiols. AHBI probe exhibited high selectivity and sensitivity, high fluorescence stability, large stokes shift and lower detection limit (15.85 ppb) for H 2 S in complete water medium. Cell imaging studies in human colon cancer cells (HCT116) and normal human dermal fibroblasts (HDF) confirmed the compatibility and versatility of AHBI probe at micromolar level. Overall, we believe the AHBI , as an optical probe will be useful to investigate the role of H 2 S in various physiological processes, regulation of cancer cell growth, and in pathogenic events. [ABSTRACT FROM AUTHOR]

• A highly selective 1,8-naphthalimide-based red-emitting ratiometric fluorescent probe Lyso-NpSN has been developed. • Probe Lyso-NpSN showed fast response to HOBr within 12 s. • Lyso-NpSN possessed excellent lysosomal targetable ability in living cells. • Lyso-NpSN could be successfully applied for ratiometrically imaging exogenous and endogenous HOBr in living cells. As one of the most important reactive oxygen species, hypobromous acid (HOBr) has been reported to be linked to a large body of diseases. Although some limited of HOBr-selective probes have been designed, there was no probes reported capable of sensing of HOBr with lysosome-targetable ability and red-emitting ratiometric fluorescence. Herein, we presented a 1,8-naphthalimide-based fluorescent probe Lyso-NpSN for rapid detection of HOBr over a wide pH range with high selectivity over other reactive oxygen species and sensitivity, for the first time. Furthermore, the probe was found to be low cytotoxicity to cells and had enabled to visualize exogenous and endogenous HOBr in living cells. [ABSTRACT FROM AUTHOR]