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Cysteine (Cys) is a significant biological mercaptan that achieves key roles in several important physiological processes, such as reversible redox homeostasis in living organisms. Abnormal levels of Cys in the human body are directly related to many diseases. In this work, we constructed a sensitive sensor (Cys-NR) by connecting a Cys recognition group to a Nile red derivative. Due to photo-induced electron transfer (PET), the Cys-NR probe showed little fluorescence at 650 nm. With the addition of Cys to the assay solution, the chlorine unit of the probe was substituted by the thiol group of Cys. Further, the amino and sulfhydryl groups in cysteine underwent an intramolecular rearrangement, which led to the Cys-NR probe water solution turning from colorless to pink with an enhancement in fluorescence. The red fluorescence at 650 nm increased about 20 times. Based on the turn-on signal, a selective Cys detection method is developed. The probe signal is not affected by various potential interferences or other competing biothiols and the limit of detection (LOD) is determined to be 0.44 μM. In addition, the probe is further employed for imaging of Cys in live cells, revealing good biological imaging ability that could provide a new way of intracellular Cys detection. [ABSTRACT FROM AUTHOR]

A novel ratiometric fluorescent probe HB‐2 based on benzothiazole for hypobromous acid (HBrO) was synthesized and studied. After HBrO was added to the CH3CN‐HEPES solution of the HB‐2, the probe cyclized to form a sulfimine bond, which increased the conjugated degree of the system. The fluorescence emission peak of the reaction system at 447 nm gradually decreased, while the newly generated emission peaks gradually increased at 580 nm. The ratio of the fluorescence intensity at the two wavelengths of 447 nm and 580 nm increased about 234 times. Moreover, it has successfully been used to stain and record microscopy images of 4T1 cells, and the presence of exogenous HBrO could be judged by the change of fluorescence intensity. [ABSTRACT FROM AUTHOR]

A fluorescent probe II, 6-azido-2-(2-hydroxyethyl)-1H-benzo[de]isoquinoline-1,3(2H)-dione with specific identification environment H2S, was designed and synthesized based on 4-bromine-1,8-naphthalimide and ethanamine. We used 4-bromine-1,8-naphthimide as raw materials to synthesize a new type of reactive fluorescent probe based on the mechanism of intramolecular charge transfer. These two materials are easily obtainable, low in cost, and can be synthesized through a simple two-step reaction. 1,8-Naphthalene anhydride has a moderate fluorescent ability as it introduces an electron-donating group at position 4. A change to its conjugate system can cause a push-pull electronic effect in the molecule and result in a very strong luminous effect. The structure of probe II was characterized by IR, ESI, and NMR. The preliminary screening was under the UV lamp. We found that probe II had a certain specific recognition effect on H2S in the DMSO solvent. After the solvent screening, DMSO was selected as a solvent to identify H2S specifically for the probe. The fluorescence spectroscopy illustrated that probe II showed green fluorescence in the DMSO solution. With the continuous addition of H2S, probe II showed red fluorescence at 510 nm, which produced a strong fluorescence emission peak that stood out from the rest of the spectrum. The experimental results showed that the probe had a very good sensitivity at detecting H2S (with a minimum concentration of 1 × 10–7 mol/L). Meanwhile, dozens of cations and anions do not interfere with the recognition of H2S by the probe molecule in the DMSO system. At the same time, we found that probe II could also recognize H2S by cell imaging technology. [ABSTRACT FROM AUTHOR]

β-Galactosidase (β-gal), an enzyme related to cell wall degradation, plays an important role in regulating cell wall metabolism and reconstruction. However, activatable fluorescence probes for the detection and imaging of β-gal fluctuations in plants have been less exploited. Herein, we report an activatable fluorescent probe based on intramolecular charge transfer (ICT), benzothiazole coumarin-bearing β-galactoside (BC-βgal), to achieve distinct in situ imaging of β-gal in plant cells. It exhibits high sensitivity and selectivity to β-gal with a fast response (8 min). BC-βgal can be used to efficiently detect the alternations of intracellular β-gal levels in cabbage root cells with considerable imaging integrity and imaging contrast. Significantly, BC-βgal can assess β-gal activity in cabbage roots under heavy metal stress (Cd2+, Cu2+, and Pb2+), revealing that β-gal activity is negatively correlated with the severity of heavy metal stress. Our work thus facilitates the study of β-gal biological mechanisms. [Display omitted] • An activatable fluorescence probe (BC-βgal) for detecting β-galactosidase was designed. • BC-βgal was high sensitivity and selectivity towards β-gal with fast response (8 min). • BC-βgal imaged the β-gal fluctuation in situ in cabbage roots. • BC-βgal evaluated the β-gal activity under heavy metal stress for the first time. [ABSTRACT FROM AUTHOR]

Nitric oxide (NO) plays important roles in both physiology and therapeutics. Nonetheless, the in-situ monitoring of NO release from most existing donors is challenging, inhibiting advanced research in both chemistry and biology. In this study, we introduce an innovative photochemotherapeutic agent that incorporates a nitroaniline NO moiety with an integrated pyrene fluorophore. This design enables controlled NO release upon light irradiation, allowing for precise quantification through a dramatic fluorescence enhancement (with a 3000-fold increase in intensity). Ultrafast spectroscopy data revealed that the NO release process is exceptionally rapid, completing within 13.3 ps. Additionally, the donor's fluorescence was successfully utilized for in situ cell imaging upon direct photoexcitation. Consequently, using this fluorescent probe enables the accurate visualization of NO release kinetics, dosage, and localization in real-time. The unique advantages of this NO donor are anticipated to significantly advance research in NO chemistry and biology. [Display omitted] • The first pyrene-based photoactivated NO donor was fabricated. • Photoactive ultrafast NO release (13.3 ps) was obtained. • Real-time NO-releasing was monitored by a strong fluorescent probe (3000-fold). • Cellular imaging was performed to demonstrate NO-releasing in situ. [ABSTRACT FROM AUTHOR]

A new coumarin-based probe 3-acetyl-7-diethylaminocoumarinthiosemicarbazone (DCT) is synthesized for Al3+ fluorescence detection in CH 3 CH 2 OH/H 2 O (6 : 4, v / v). The fluorescence intensity at 428 nm was enhanced about 15-fold with the fluorescence changed from colorless to blue. The binding constantof Al3+ with DCT is 5.04 × 106 M−1. The limit of detection (LOD) of Al3+ is calculated to be 82 nM. Furthermore, the binding details are determined by Job's plot and ESI - MS studies, which indicated that a stoichiometric ratio of 1 : 1 complex is formed between Al3+ and DCT. Cell imaging confirmed that DCT could useful for detecting Al3+ in HepG2 cells. • Probe DCT is highly selective and sensitive towards Al3+in aqueous solution phase with LOD is 82 nM,which could monitor intracellular Al3+ levels. • The mechanism indicated that a ratio of 1 : 1 complex is formed between Al3+ and DCT. [ABSTRACT FROM AUTHOR]

The fluorescence behaviors and applications of two water‐soluble imidazolium analogs TPI‐1 and TPI‐2 with D‐π‐A structures have been studied. Compound TPI‐1 possessed the aggregation‐induced emission (AIE) effect, but TPI‐2 not. Moreover, compound TPI‐1 could serve as a fluorescence turn‐on probe for detecting uridine‐5'‐triphosphate (UTP) in living cells by AIE mechanism, while TPI‐2 was able to penetrate into the cell membranes and light up the living cells. [ABSTRACT FROM AUTHOR]

On account of long wavelength emission and high stability, a hemi-cyanine skeleton of 2,3,3-trimethyl-1-(3-sulfopropyl)-3H-benzo[f]indolinium was condensed with 6-hydroxy-7-morpholin-4-yl-methyl-naphthalene-2-carbaldehyde in the presence of acetic anhydride. The new probe displays a sensitive absorption and fluorescence according to the pH value changes and exhibits an excellent linearity of the relative emission intensity (I670/I580) vs. pH in the pH range of 7.0–9.5 with a correlation coefficient of 0.993. Moreover, compared to the commercialized LysoTracker Green DND-26 the probe is targeting to the lysosomal imaging in HeLa cells and, thus, can be further used as a near-infrared fluorescent probe for cellular research. [ABSTRACT FROM AUTHOR]

A novel ratiometric fluorescence probe for hypochlorous acid was constructed by coumarin and pyridinium fluorophore based on the Forster resonance energy transfer (FRET) and intramolecular charge transfer (ICT) platform. In this ICT/FRET system, the energy transfer efficiency is high to 94.3%. Moreover, the probe could respond to hypochlorous acid with high selectivity and sensitivity, and exhibited a large Stokes shift. It was interesting to find that the probe could recognize hypochlorous acid via a new mechanism, in which the α-position of carbonyl group was oxidized to form a diketone derivative. More importantly, the probe was successfully applied to the ratiometric imaging of both exogenous and endogenous hypochlorous acid in living RAW 264.7 cells, with low toxicity and high photo-stability. Image 1 • A ratiometric fluorescent probe ZPAC for rapidly monitoring hypochlorous acid. • A new mechanism, α position of carbonyl group was oxidized to form a diketone derivative. • FRET-based ZPAC displayed larger gap between two emission spectrum. • ZPAC was applied to image exogenous and endogenous hypochlorous acid in living RAW264.7 cells. [ABSTRACT FROM AUTHOR]

Stimulation emission depletion (STED) microscopy enables ultrastructural imaging of organelle dynamics with a high spatiotemporal resolution in living cells. For the visualization of the mitochondrial membrane dynamics in STED microscopy, rationally designed mitochondrial fluorescent markers with enhanced photostability are required. Herein, we report the development of a superphotostable fluorescent labeling reagent with long fluorescence lifetime, whose design is based on a structurally reinforced naphthophosphole fluorophore that is conjugated with an electron-donating diphenylamino group. The combination of long-lived fluorescence and superphotostable features of the fluorophore allowed us to selectively capture the ultrastructures of the mitochondrial cristae with a resolution of ~60 nm when depleted at 660 nm. This chemical tool provides morphological information of the cristae, which has so far only been observed in fixed cells using electron microscopy. Moreover, this method gives information about the dynamic ultrastructures such as the intermembrane fusion in different mitochondria as well as the intercristae mergence in a single mitochondrion during the apoptosis-like mitochondrial swelling process. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new lysosome-targeted fluorescent probe FAP1 for the recognition of FA was developed. • Probe FAP1 showed high sensitivity and selectivity for detecting FA with a large Stokes shift (130 nm). • Probe FAP1 exhibited good biocompatibility and could be used to image FA in lysosome. Formaldehyde (FA) is one of reactive carbonyl species (RCS), which is involved in various physiological and pathological processes of organisms. Herein, a novel fluorescent probe (FAP1) containing lysosomal localization group for the detection of FA was designed and synthesized. The probe exhibited good fluorescence recognition performances for FA, such as large Stokes shift (130 nm), specific selectivity, good anti-interference ability, and low minimum detection limit (16 nM). It is worth mentioning that the probe has good biocompatibility and could be applied to the imaging detection of FA in lysosome. [ABSTRACT FROM AUTHOR]

An acid‐treated, oxidized graphitic carbon nitride nanosheets (g‐C3N4 NSs) was successfully synthesized and applied as a fluorescence probe for the detection of hemin based on the inner filter effect (IFE). The results indicated that the fluorescence quenching of g‐C3N4 NSs caused by hemin was attributed to the overlap between absorption spectrum of hemin and emission spectrum of g‐C3N4 NSs. It is confirmed that the g‐C3N4 NSs exhibited a highly sensitive and selective for detection of hemin. Under the optical condition, the fluorescence changing of g‐C3N4 NSs is related to the concentration of hemin ranging from 0.5 – 25 μM with a detection limit of 0.15 μM. Moreover, the fluorescence probe has been successfully applied to detect hemin in human blood. Overall, a novel and efficient fluorescence‐based method was developed supported by g‐C3N4 NSs, which is a promising material for application in sensing and cell imaging. [ABSTRACT FROM AUTHOR]

A turn on fluorescence probe for the rapid detection of hypochlorite (ClO−) was prepared successfully. The detection performances of this probe were studied by virtue of ultraviolet absorption and fluorescence spectroscopy. The results demonstrated that this probe displayed excellent colorimetric and noteworthy fluorescence enhancement after interaction with hypochlorite (ClO−) and showed good selectivity and sensitivity for ClO− over other analytes in solution. Due to the short reaction time, high selectivity and sensitivity, this probe was successfully used in the detection of ClO− in living cells and water samples. [ABSTRACT FROM AUTHOR]

Abstract Three new rhodamine based probes 1 , 2 , 3 were synthesized and acted as fluorescence probes for Hg2+ detection in Tris - HCl/C 2 H 5 OH (v : v = 3: 7, 10 mM, pH = 7.2). Hg2+ induced a colorless solution of probes 1 , 2 , 3 to turn to naked-eye visible pink with a 44 - fold fluorescence enhancement at 576 nm. Probes 1 , 2 , 3 are highly selective to Hg2+ over other tested cations with the detection limits are 18 nM, 16 nM, 56 nM, respectively. What's more, the binding constants between probes 1 , 2 , 3 and Hg2+ are 5.0 × 106 M−1, 1.8 × 106 M−1, 1.5 × 106 M−1, respectively. The different detection limits and binding constants of probes 1 , 2 , 3 and Hg2+ may depend on the coordination of probes 1 , 2 , 3. The recognition mechanism of probes 1 , 2 , 3 towards Hg2+ is determinated by ESI - MS, DFT and indicates that a ring-opening of the spirolactam unit and formed complexes between probes 1 , 2 , 3 , resulting in chromogenic and fluorogenic changes. The probes 1 , 2 , 3 could be applied in both environmental and Hg2+ polluted samples due to the instantly and reversible "off-on" Hg2+ response, well cell permeability, cell imaging ability. Graphical abstract Rhodamine based "turn-on" chemodosimeter exhibited instant/reversible and excellent specificity towards Hg2+ in aqueous media and living cells. fx1 [ABSTRACT FROM AUTHOR]

Abstract A simple asymmetric hydrazone 1 based on salicylaldehyde was designed and prepared, and exhibited an evident aggregation-induced emission (AIE) at a long wavelength of 570 nm in aqueous medium. Probe 1 can selectively sense Al3+ in CH 3 OH solution through the chelation-enhanced fluorescence mechanism and also recognize Cu2+ via fluorescence quenching in H 2 O solution through the Cu2+-induced assembly of aggregates. In addition, the probe can be applied for detecting Cu2+ in biological samples. Graphical Abstract Unlabelled Image Highlights • A simple Schiff base-based fluorescent sensor for Cu2+ in aggregation states has been developed. • The sensor could also detect Al3+ in CH 3 OH solution with fluorescence enhancement. • The sensor is an aggregation induced emission active compound with emission at a long wavelength of 570 nm. • The sensor has been used for imaging of Cu2+ in living cells. [ABSTRACT FROM AUTHOR]

Thiazole orange ( TO ) stains most nucleic acids giving strong fluorescence signal non-specifically. To resolve the poor discriminating ability of TO among tertiary structures of DNAs, a planar and rotatable π–conjugated small molecule designed by replacing the methylene bridge with an ethylene that slightly increases its structural flexibility, while maintain the crucial conjugated co-planar two-ring system. The study addressed the origin of signal discrimination for the molecule upon binding with different DNA structures and the results demonstrate that the molecule exhibits excellent fluorescence signal discrimination between the DNA G-quadruplexes and other DNA tertiary structures. In a typical staining assay, the molecule induced 30-fold greater fluorescence signal upon binding with Pu27 than that of ssDNA and dsDNA. Molecular modelling studies also support that the flexible ethylene bridge between the two-ring system is the crucial factor for inducing selectivity towards G-quadruplexes. Furthermore, the selectivity, sensitivity, and stability of the molecule were investigated with various techniques. The application of the molecule as a selective staining agent for imaging of G-quadruplex in human prostate cancer cells PC3 and mouse fibroblast L929 was also investigated. The strongly observed green fluorescence signal in the cell nucleus suggests that the molecule is able to enter into the nucleus and then binding with G-quadruplexes. [ABSTRACT FROM AUTHOR]

In this paper, a novel fluorescent probe HBT-H based on benzothiazole has been designed and synthesized. The probe has excellent selectivity and can be used for specific detection of Cu2+. Under 360 nm UV excitation, the probe HBT-H itself has a fluorescence emission peak at 487 nm, emitting cyan blue fluorescence, fluorescence quenching after added Cu2+. The detection limit of Cu2+ recognition by HBT-H probe was calculated as 3.08 × 10−7 M. According to Job's plot and high resolution mass spectrometry, the complexation ratio of HBT-H to Cu2+ was 2:1. The sensor mechanism was confirmed as excited intramolecular proton transfer (ESIPT). Surprisingly, the probe HBT-H system responded well to pH, showing green fluorescence under acidic conditions and cyan blue fluorescence under alkaline conditions. In addition, the probe HBT-H has excellent membrane permeability and low cytotoxicity, which could not only detect Cu2+ in actual water samples, but also recognize Cu2+ in human breast cancer cells (MCF-7). [Display omitted] • The probe could selectively detect Cu2+ from solutions or water samples. • The detection limit of Cu2+ with this probe was as low as 3.08 × 10−7 M. • The probe could be used to judge the acid-base properties colorimetrically. • The probe was successfully applied to the imaging of human breast cancer cells. [ABSTRACT FROM AUTHOR]

[Display omitted] • An indene-chalcone-based fluorescence probe with lysosome-targeting has been developed. • The crystal structure of the probe was reported. • The probe could monitor carboxylesterase (CEs) with a short response time (20 min), low detection limit (1.3 × 10−4 U/mL) and large stokes shift (155 nm). • The probe has been successfully applied to the imaging of endogenous CEs in the lysosomes of living cells and zebrafish. An indene-chalcone-based fluorescence probe 1 was synthesized and characterized. Under physiological conditions (containing 5% DMSO), probe 1 showed satisfactory stability with a low background signal and recognized carboxylesterases (CEs) based on the catalytic hydrolysis of ester groups, releasing a significant green fluorescence. Probe 1 presents several features including a short response time (within 20 min), low detection limit (1.3 × 10−4 U/mL) and large stokes shift (over 155 nm). Notably, commercial lysosomal dye co-staining experiments illustrated the lysosomal localization function of 1 , with the probe also being used for cell and zebrafish imaging of endogenous CEs. [ABSTRACT FROM AUTHOR]

Mercury ions (Hg2+) are recognized as the typical inorganic contamination that can cause severe damage to the environment and humans. In this paper, boron-doped carbon quantum dots (B-CQDs) with a fluorescence quantum yield (QY) of 10.4% and good photoluminescent properties were synthesized via a one-step hydrothermal method using citric acid and histidine as the carbon source and borax as the provider of boron. The obtained B-CQDs exhibited a bright blue emission under excitation wavelength of 365 nm. As a fluorescent probe, it appears excellent selectivity and sensitivity to assay Hg2+. When Hg2+ were added to B-CQDs, its bright blue fluorescence was obviously quenched. Under optimum conditions, the sensor shows a wide linear range (0 ~ 150 μM) and a low detection limit (2.5 μM). Interestingly, the quenched fluorescence of B-CQDs containing Hg2+ could be turned on by adding reducing agent EDTA-2Na or I-. Furthermore, it was applied successfully to assay Hg2+ in real sample. More importantly, B-CQDs was found to be nontoxic and can be used as bioimaging agent for MCF-7 cell labeling. The possible fluorescence quenching mechanisms of the probe are also discussed in detail. This study provides a new approach for fabricating a multifunctional fluorescent probe and a prospective application in environmental monitoring. [Display omitted] • B-CQDs were successfully synthesized by one-step hydrothermal method. • B-CQDs as fluorescent probe were specific for Hg2+ with low detection limit and wide linear range. • B-CQDs were used for Hg2+ determination with selectivity, immunity and recovery. • B-CQDs were successfully applied to assay Hg2+ in tap water. • B-CQDs as the fluorescent marker could label MCF-7 cancer cells. [ABSTRACT FROM AUTHOR]

• Excluding interference and detecting microcystin-LR based unique fluorescence method. • The performance of MC-BDKZ was tested by calculating recovery rate in water samples. • MC-BDKZ showed excellent fluorescence imaging to intracellular MC-LR and lysosome. • The response mechanism of MC-BDKZ to MC-LR was deeply discussed. Cyanobacteria blooms that cause the death of aquatic and terrestrial organisms have attracted considerable attention since the 19th century. The most typical toxin in cyanobacteria blooms is cyanobacteria toxin, particularly microcystin-LR (MC-LR). Therefore, a simple and highly efficient method for detecting MC-LR plays a role in studying the ecological toxicology of MC-LR. However, as MC-LR itself is located in a complex environment, traditional techniques present complex and false-positive defects. To address the above issues, novel technologies should be explored and discovered. Herein, we describe the development of MC-BDKZ as the first paradigm of probes that can concurrently report MC-LR in natural lakes and cells. This novel material shows large Stokes Shift and possesses good photostability and high sensitivity. Considering the properties mentioned above, MC-BDKZ not only achieves the detection of MC-LR in the lake water samples, but also completes the imaging of exogenous MC-LR in cells. Moreover, the interference of many factors in the lake and cells is excluded completely in the process of MC-LR detection. We comprehensively analyzed the response principle and potential application of MC-BDKZ in the process of MC-LR detection. Compared with the conventional MC-LR detection technologies, fluorescence probe technology shows better convenience and greatly reduces distance from the practical application in vitro and in vivo. We envisioned that the development of this visual research tool could provide crucial clues for exploring the pathogenesis of MC-LR in body. [Display omitted] [ABSTRACT FROM AUTHOR]

Detection and imaging of Cysteine (Cys) and Homocysteine (Hcy) in living systems have drawn extensive attention over the years due to their significant biological role. However, few fluorescence probes have been reported to distinguish Cys and Hcy in near-infrared (NIR) range. In this paper, an original NIR Cys and Hcy fluorescent probe, namely DTRN , was synthesized. DTRN was constructed by using an acryloyl ester group as a trigger and dicyanoisophorone-derived as the fluorophore unit, it was found to emit NIR fluorescence with a 718 nm emission and have large stokes shift (∼176 nm). DTRN hold excellent performances such as ultrasensitivity (LOD = 0.09 μM), high specificity and fast response (<2 min) for Cys. Distinctly, after Hcy was introduced, the emission intensity of DTRN at 718 nm must take 20 min to reach a plateau and the LOD was found to be 0.12 μM. The sensing mechanism for Cys and Hcy in C 2 H 5 OH/PBS (4/6, v/v, pH = 7.4) was studied by 1H NMR spectroscopy and HRMS. Most importantly, the ability of DTRN to detect Cys in HeLa cells had also been achieved. A NIR fluorescent probe (DTRN) was synthesized by using acryloyl ester group as a trigger and dicyanoisophorone-derived as the fluorophore unit, it can detect Cys and Hcy emit NIR fluorescence at 718 nm and have large stokes shift (∼176 nm). [Display omitted] • A NIR fluorescent probe (DTRN) with large stokes shift (∼176 nm) was synthesized. • DTRN could distinguish Cys and Hcy by time-dependent fluorescence signals. • The LOD for Cys and Hcy was calculated to be 0.09 μM and 0.12 μM. • DTRN was successfully exploited for detecting Cys in HeLa cells. [ABSTRACT FROM AUTHOR]

• The probe exhibited excellently selective and sensitive detection for Hg2+ over other relevant analytes. • The fluorescent response was fast within 120 s and a dramatic color changes (from colorless to light green) could be observed by naked eyes. • The detection limit of the probe was 0.019 μM. • The probe was successfully applied to detecting Hg2+ in real water samples and HeLa cells. Mercury ions are highly toxic to living organisms and environment, hence Monitoring and quantification of mercury ions remain great significance. Herein, we have designed and synthesized a novel reaction-based fluorescence probe RANS for detection of Hg2+ by using a xanthene derivate as fluorophore and a thiosemicarbazide moiety as the recognition site. By applying mercury-promoted desulfurization reactions, probe RANS exhibited excellent capability of detecting Hg2+, such as rapid response (120 s), high sensitivity (0.019 μM) and good selectivity. Upon reaction with Hg2+, the thiosemicarbazide group of probe RANS formed 1,3,4-oxadiazole along with a significant color change from colorless to light green. Importantly, RANS has been successfully applied to selectively imaging Hg2+ in living cells with low cytotoxicity and quantitative detection of Hg2+ in real water samples. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • The probe specially detected palladium based on Pd0-mediated Tsuji-Trost reaction. • The probe could selectively detect palladium with large Stokes shift (155 nm). • The dramatic color changes (from colorless to blue) could be observed by naked eyes. • The detection limit of the probe was 0.140 μM. • The probe was successfully applied to detecting palladium in real water samples and HeLa cells. Nowadays, palladium has been widely used in many fields, which facilitates all aspects of our life. However, it may cause water and soil pollution and bring irreversible damage to the environment and organisms. Developing a fluorescence probe for rapid, highly sensitive and selective detection of palladium is still a poser. In this work, we designed and synthesized a novel fluorescence probe (RHS) for specific detection of palladium. Based on Pd0-mediated Tsuji-Trost reaction, the fluorescence probe was constructed by a rhodol derivative as the fluorophore and an allyl carbonate moiety as the specific palladium reactive site. The probe displayed excellent properties for detecting palladium, such as high selectivity and sensitivity, rapid response (20 min) and large Stokes shift (155 nm). The detection limit was determined to be as low as 0.140 μM with a linear range from 20 to 80 μM. After addition of palladium in RHS solution, the color of the solution turned from yellow to blue, indicating palladium could be monitored by the naked eyes. Moreover, probe RHS was successfully applied to palladium detection in environmental water samples. Importantly, with low cytotoxicity and good biocompatibility, the probe could monitor palladium in living cells. [ABSTRACT FROM AUTHOR]

[Display omitted] • The probe was designed and synthesized based on a rhodol derivate anchored with the 2,4-dinitrophenyl group. • The fluorescent response was fast within 12 min and a dramatic color change (from colorless to pink) could be observed by naked eyes. • The detection limit of the probe was 0.097 μM. • The probe was successfully applied to detecting H 2 S in real water samples and HeLa cells. In this work, a reaction-based fluorescence turn-on probe RCHO, a rhodol derivate anchored with the 2,4-dinitrophenyl moiety, was designed and synthesized for H 2 S detection. The 2,4-dinitrophenyl moiety, as an electron-withdrawing group, was used for quenching the fluorescence of the fluorophore. The probe RCHO could quantitively detect H 2 S with high selectivity and fast response by introducing aldehyde groups in the ortho position of 2,4-dinitrobenzene. After addition of H 2 S, H 2 S was quickly added to the aldehyde group through a nucleophilic addition reaction, and then the dinitrophenyl ether underwent effective intramolecular thiolysis, which resulting in the release of the fluorophore and a rapid fluorescence turn-on response. The detect limit was calculated to be 0.097 μM. Furthermore, in the presence of H 2 S, a remarkable color change from colorless to pink was observed, indicating that the probe RCHO could monitor H 2 S by the naked eyes. More importantly, the probe could be used as a highly efficient tool for H 2 S detection in living cells and environmental water. [ABSTRACT FROM AUTHOR]

[Display omitted] • Multi-color, high quantum yield, good stability of quantum dots were synthesized. • The fluorescence intensity and QY of quantum dots had a good temperature dependence. • Low temperature could improve the fluorescence properties of quantum dots. • The fluorescence imaging of liver cells was successfully demonstrated at −20 °C. In this paper, CdSe/ZnS quantum dots (QDs) with particle size of 5.5 ~ 9.3 nm were synthesized, and the fluorescence emission ranged from 545 ~ 616 nm. When the volume fraction of ethanol was 30%, the water-soluble QD dispersion system remained liquid under −20 °C freezing conditions, the fluorescence intensity increased with a decrease in temperature, and the quantum yield reached 79% at −20 °C. The endothelial cell adhesion molecule CD31 antibody (anti-CD31) was used as the primary antibody, QDs were coupled with IgG as the secondary antibody (QD-Ab), and effective labeling of hepatic sinusoid endothelial cells was achieved at −20 °C. Fluorescence imaging and flow cytometry analysis showed that the labeling efficiency was as high as 97%, indicating that QDs have an important application prospect in microscopic section tomography of the liver. [ABSTRACT FROM AUTHOR]

The detection of metal ions is of particular importance for monitoring environmental pollution and life metabolic activities. However, it is still a challenge to achieve Fe3+ detection with specific sensitivity and rapid response, especially in the presence of chelating agents for Fe3+ ions. Herein, a novel fluorescence probe for Fe3+, i.e., amide derivative of [1,2,4]triazolo[1,5-a] pyrimidine (TP, Id), was synthesized, featuring specific Fe3+ selectivity, rapid quenching (5 s), low limit of detection (0.82 μM), good permeability and low cytotoxicity. More importantly, Id can be used to identify and detect Fe3+ in the presence of existing strong chelating agents (e.g., EDTA) for Fe3+ ions. The results show that the as-synthesized fluorescence probe is particularly suitable as a bioimaging reagent to monitor intracellular Fe3+ in living HeLa cells. Furthermore, we proposed the binding mode for Id with Fe3+ ions and the light-emitting mechanism through high-resolution mass spectra and density function theory calculations, respectively. An Id -based test paper can be used to rapidly identify Fe3+. These results are expected to improve the development of new sensitive and specific fluorescent sensors for Fe3+. [Display omitted] • A novel amide derivative of [1,2,4]triazolo[1,5-a]pyrimidine fluorescence probe Id for Fe3+ ions was first reported with specific, rapid response to Fe3+ ions and low cytotoxicity. • The probe Id could detect Fe3+ ions in the presence of strong chelating agents (e.g., EDTA) of Fe3+ ions and the Id -based test paper could identify Fe3+ ions rapidly. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel dual-functional fluorescence probe has been developed to detect Al3+ and Mg2+. • The probe can monitor Al3+ and Mg2+ in living cells with different responses. • The response of probe towards Al3+ and Mg2+ is ascribed to multifarious mechanisms. • The fluorescence intensity of probe towards Al3+ increases about 2556-folds compared with free probe. The metal cations, Al3+ and Mg2+, could affect human health and cell biological processes. Their fast and selective detection using one probe remains a challenge. A novel fluorescence probe, N'-((1-hydroxynaphthalen-2-yl)methylene)isoquinoline-3-carbohydrazide (NHMI), was developed for selectively monitoring Al3+ and Mg2+. The probe NHMI showed a distinctive "turn-on" fluorescence signal towards Al3+ and Mg2+ (cyan for Al3+ with 2556-folds enhancement and yellow for Mg2+ with 88-folds enhancement), which is quite distinct from other metal cations and allows for naked-eye detection. This interesting response was attributed to the influence of PET, ESIPT process and CHEF effect, when Al3+ or Mg2+ chelated with NHMI. Furthermore, the fluorescence titration experiments manifested that the detection limit of probe NHMI for Al3+/Mg2+ was as low as 1.20 × 10–8 M and 7.69 × 10–8 M, respectively. The formed complexes NHMI-Al3+ and NHMI-Mg2+ were analyzed by Job's plot, ESI-MS, 1H NMR and FT-IR. The coordination pockets and fluorescence mechanisms of two metal complexes were explored by density functional theory calculation. Moreover, NHMI showed low cytotoxicity and good cell permeability. Fluorescence bioimaging of Al3+/Mg2+ in MCF-7 cells with NHMI indicated its potential application in biological diagnostic analysis. [ABSTRACT FROM AUTHOR]

Cyanide detection methods are urgently needed due to the highly lethal to human beings. Herein, we report two fluorescence probes (Probe 1 and Probe 2) based on cyanoethylene group for cyanide anion (CN−) detection. The selective recognition for CN− was confirmed by the completely opposite green fluorescence of Probe 1 and red fluorescence of Probe 2 observed by fluorescence spectra and naked eyes. The probes take advantages of the large Stokes shift (~160 nm), rapid response (30 s), anti-interference performance and low detection limit (Probe 1 : 12.4 nM, Probe 2 : 101 nM). The sensing mechanism is certificated to the nucleophilic attack of CN− to electron-deficient cyanoethylene group of probes, which was demonstrated by 1H NMR titration, HR-MS, Job's plot and IR spectroscopy. Density functional theory (DFT) calculations were carried out to analyze the mechanism in theory. Further, practical applications were studied. Easy-to-use test strips treated with Probe 1 or Probe 2 are capable of CN− detection in pure drinking water. The good biocompatibility and membrane penetrability have achieved the bioimaging capability of Probe 1 and Probe 2 in living HepG-2 cells, making the probes promising for use in real lives. [Display omitted] • Probes show high selectivity towards cyanide (CN−) and good anti-interference ability against other competing anions. • Probes show high reactivity in aqueous media, making them can be used in actual environment and biological system. • Probes are capable of CN− detection by easy-to-use test in pure drinking water. • Probes have large Stokes shifts and low cytotoxicity so that they can be utilized as CN− sensors in living cells. [ABSTRACT FROM AUTHOR]

With the development of biotechnology, luminescent nanoprobes for biological disease detection are widely used. However, the further application in clinic is limited by the reduced penetration depth in the tissues and light scattering. In this work, we have synthesized NaYF4:Yb,Er,Ce@SiO2-OAlg nanomaterials, which have both upconversion and near-infrared (NIR) luminescence. The optimized probes were determined to achieve cell imaging by its upconversion (UCL) luminescence and in vivo imaging through collection of NIR fluorescence signals simultaneously. The research is conducive to developing accurate diagnostic techniques based on UCL and NIR fluorescence imaging by a single nanoparticle. [ABSTRACT FROM AUTHOR]

Scutellaria baicalensis is one of the widely used Chinese traditional medicines, and wogonin is one of major active components in it. However, the mechanism of action of wogonin has largely remained unclear. In this work, we designed a fluorescent probe, namely ATTO565-WGN, by conjugating wogonin with the fluorophore ATTO565 based on Mannich reaction via a flexible chain linker. In vitro assays verified that the ATTO565-WGN conjugate has a similar anti-proliferative activity to wogonin against human A549 and HeLa cancer cell lines. Combining co-localization and competition studies, confocal fluorescence imaging clearly demonstrated that the fluorescent wogonin probe predominantly located in mitochondrial area of living cells, indicating that wogonin acts at mitochondrion to exert its pharmacological functions. Significantly, the conjugated ATTO565 fluorophore conferred the wogonin probe STED (Stimulated Emission Depletion) feature, enabling STED fluorescence living cell imaging with a 55 nm of ultrahigh spatial resolution. This will greatly beneficial for the in situ investigation of interactions between wogonin and biological targets at the finely organized and dynamic mitochondria of living cells. Moreover, this work also provides novel insights into rational design of mitochondrion targeting fluorescence probes for ultrahigh resolution living cell imaging. [Display omitted] • A fluorescent probe of wogonin was synthesized and applied for living cell imaging. • ATTO565 conferred the probe STED feature without altering bioactivity of wogonin. • CLSM imaging unraveled that wogonin predominantly targets mitochondrion. • STED feature enabled localization of wogonin under ultrahigh spatial resolution. [ABSTRACT FROM AUTHOR]

[Display omitted] • A rational design of probe Chol-6RN strives to minimize the interference between recognition moiety and functional moiety. • The probe Chol-6RN is better than the control probe Chol-RN in the linearity and the detection limit. • The cell imaging experiments show that Chol-6RN has good biocompatibility and membrane permeability. To improve the sensitivity and detection limit of probe, we made good use of the advantage of 6-carboxyrhodamine to design a new cholesterol-conjugated fluorescent probe Chol-6RN for Cu2+ detection. The probe Chol-6RN exhibits a sensitive response towards Cu2+ by fluorescence spectrum in aqueous solution. The linearity of Chol-6RN is from 5 μM to 40 μM of Cu2+ with an excellent linear correlation (R2 = 0.99110) and the detection limit for Cu2+ is 1.12 μM, they are better than the control probe Chol-RN. The MTT assay indicates that Chol-6RN is negligible cytotoxicity to HeLa cells after 24 h at a concentration less than 30 μM. The cell imaging displays that Chol-6RN is capable of detecting Cu2+ in live cells and the sensibility of Chol-6RN is better than Chol-RN. [ABSTRACT FROM AUTHOR]

A bisphenol based fluorescence "turn-on" chemosensor 4,4′-(propane-2,2-diyl)bis(2-((E)-(2-(benzo[d]thiazol-2-yl)hydrazineyldene)methyl)phenol) (BHMP) has been synthesized and its sensing behavior was tested towards various ionic species. The chemo-sensing behavior of BHMP has been established through absorption, fluorescence, NMR, and mass spectroscopic techniques. The probe BHMP selectively detects zinc ions over other metal ions and the resulting BHMP + Zn2+ ensemble serves as a secondary probe for the detection of pyrophosphate (PPi) anion specifically over other anions. The spectroscopic studies reveal the fluorescence enhancement of BHMP in association with Zn2+ ions was quenched in the presence of pyrophosphate (PPi) anions. A probable mechanism of this selective sensing behavior was described on the basis of "OFF-ON-OFF" strategy for detection of both cations and anions. Moreover, the biological applicability of the chemosensor BHMP was examined via cell imaging studies. A bisphenol based fluorescence "turn-on" chemosensor (BHMP) has been synthesized and its sensing behavior was tested towards various ionic species. The probe BHMP selectively detects zinc ions over other metal ions and the resulting Zn2+-BHMP ensemble serves as a secondary probe for the detection of PPi anion. The biological applicability of the chemosensor BHMP was examined via cell imaging studies. Unlabelled Image • The probe BHMP selectively detects zinc ions and the resulting Zn2+- BHMP ensemble is applied for the detection of PPi ions. • The probe detects Zn2+ and PPi ions with low detection limit of 0.28 and 0.87 nM respectively. • The probe was successfully applied to detect Zn2+ and PPi ions in live cells. [ABSTRACT FROM AUTHOR]

Long and real time imaging of cell membrane is very important for better understanding of cell performances in physiological and pathological processes. Nowadays, fluorescence probe analysis has become an indispensable tool for monitoring cell membrane. Herein, a novel fluorescent probe based on specific recognition of GABA A receptor was developed for imaging cell membrane. The probe synthesized in this work has been successfully applied to image different kinds of cell membrane with some advantages over the reported probes. Moreover, the probe also showed good superiority in the preliminary screening GABA A drugs. Image 1 • A novel fluorescent probe based on GABA A receptor was developed for imaging membrane. • The probe was successfully applied to image many kinds of cell membrane. • The probe shows many advantages over reported probes designed for imaging membrane. • The probe was attempted preliminarily to use as a tool for screening GABA A drugs. [ABSTRACT FROM AUTHOR]

Intracellular pH is a key physiological factor for controlling the activities and functions of cells and lysosome is a vital subcellular organelle. Thus, developing a novel lysosome-targeting fluorescence probe for selective and sensitive detection of lysosomal pH in living cells is very important. In this work, we synthesized a series of fluorescence probes based on imidazole-fused benzothiadiazole. The optical properties of these probes were easily adjusted by modifying the substituents with different electron-withdrawing/donating ability in imidazole moiety. All of them showed acid-response and decreased fluorescence intensity during pH values changing from 4.0 to 8.5. The introduction of morpholine group allowed them to specifically respond to the changes of lysosomal pH. Among them, probe MIBTAA possessed a suitable p K a value (5.3) and showed good linear response to pH (R2 = 0.9918) with red emission when pH changed from 4.4 to 5.6. The probe was successfully applied for monitoring pH variation in living cells induced by proton-pump inhibitor Baf-A1 and chloroquine, indicating its great potential for pH imaging in biological applications. A series of fluorescence probes based on imidazole-fused benzothiadiazole scaffold were developed for pH sensing. Image 1 • A series of fluorescence probes were designed and synthesized for pH measurement. • The probes were based on imidazole-fused benzothiadiazole molecular skeleton. • The optical properties of fluorescence probes were regulated by different electron-withdrawing/donating substituents. • The lysosomal pH changes were successfully monitored by probe MIBTAA. [ABSTRACT FROM AUTHOR]

Developing a specific and sensitive method for endogenous hydrazine detection in living systems is valuable to understand its various pathological events. In this work, two novel fluorescent chemosensors (C1, C3) based on triphenylamine Schiff-base derivative and reference dyes (C2, C4) were prepared in relatively high yield (more than 72% yield). The aggregation induced emission (AIE) properties of sensors were investigated through UV–Visible, dynamic light scattering, X-ray diffraction, fluorescence spectrophotometric analyses as well as scanning electron microscope images (SEM). The results indicated that probes C1 and C3 exhibited strong AIE property in DMF/H 2 O (1:1, v/v) mixture system with brilliant yellow fluorescence emission (560 nm) observed under 365 nm UV lamp. The experiments of sensing indicated that probes C1 and C3 possessed the sequentially detecting abilities for hydrazine with high sensitivity, specificity as well as an extremely low detection limit (55.1 nM), which was due to blocking of AIE process of probes C1 and C3 by special chemical reaction (-CH N- moiety transformed into –CH 2 -NH- group) after hydrazine addition, resulting in the increase in water solubility and a weak emission in aqueous media. Furthermore, 1H NMR, SEM and fluorescence titration experiment was also conducted to confirm the sensing mechanism. For biological application, probes C1 and C3 presented a good bio-imaging performance and showed the similar fluorescence quenching after adding hydrazine. Therefore, the probes are suitable for the fluorescence imaging of exogenous hydrazine in HeLa cells. Image 1 • Synthesis of conjugated chromophores carrying ESIPT segments. • A novel 'turn-on' probes for hydrazine based on ESIPT segments with AIE properties have been successfully obtained. • Detection abilities for hydrazine with high sensitivity, specifity and lower limit of detection (LOD). • The sensitivity of probe is demonstrated successfully for selective imaging of hydrazine in living cells. [ABSTRACT FROM AUTHOR]

The intracellular pH has a significant effect on several essential biological processes such as material transfer, enzymatic action, cell apoptosis et al. Thus, it is necessary to monitor pH fluctuation in living cells. Here, we designed a near-infrared ratiometric fluorescence probe for pH detection. The spectroscopic responses of probe to pH variations were investigated in CH 3 OH/PBS (v/v, 1:1) mixed solution at different pH values. The experimental results showed that the probe is sensitive to acidity, and the p K a of probe is calculated to be 4.85. When the pH was decreased from 9.0 to 1.0, the color of probe solution change from purple to yellow was found by naked eye. Moreover, the probe can be a practical tool for assessing cellular pH by cell imaging. Unlabelled Image • A near-infrared ratiometric fluorescence probe based on spiropyran derivative for pH was obtained. • The conversion between acid and alkaline form of the probe is reversible and rapid (within 10 s). • The probe can be applied to monitor cellular pH. [ABSTRACT FROM AUTHOR]

Red emissive B,N co-doped carbon dots (BN-CDs) were hydrothermally synthesized from cresyl violet and boric acid. The BN-CDs exhibited excellent photostability, low cytotoxicity, excitation/emission maxima at 520/616 nm, and a relatively high quantum yield of 18%. The BN-CDs can binded to mercury(II), and this results in quenching of the red-colored fluorescence. However, on subsequent addition of the biothiol (such as cysteine, homocysteine or glutathione), fluorescence recovers. Therefore, the BN-CDs can be used as a multifunctional probe based on "on-off-on" fluorescence response for the detection of Hg(II) and biothiols. The following detection limits were accomplished: (a) Hg(II): 2.8 μM; (b) glutathione: 1.7 μM; (c) cysteine: 2.3 μM; (d) homocysteine: 3.0 μM. The BN-CDs also have been successfully applied for the imaging of Hg(II) and biothiols in HepG2 cells with excellent bio-compatibility. [ABSTRACT FROM AUTHOR]