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Five novel dual-state emissive imidazo[1,2- α ]pyridine-based luminogens IP1-5 were rationally designed and prepared by varying the conjugation length and the nature of donor-acceptor (D-A) units. These D-A chromophores displayed cyan, green, yellow, and red fluorescence in the solid state, with full-color emission achieved for the first time through modification of imidazo[1,2- α ]pyridine core. Interestingly, IP1 and IP5 in the solid state exhibited an abnormal remarkable blue-shift emission compared with those in THF, probably due to the highly twisted molecular conformations and solvent effect by theoretical calculations as well as crystal structure analyses. Importantly, IP1-5 revealed remarkable reversible acid-induced acidichromism, accompanied with dual change of colorimetric and fluorometric determination. Viscosity-dependent fluorescence was next conducted, indicting IP1-3 can be utilized for local viscosity detection. Moreover, IP1-5 served as promising candidates for multicolor bioimaging with low cell toxicity and good biocompatibility. Five asymmetric donor-acceptor dual-state emissive imidazo[1,2- ɑ ]pyridines have been synthesized with full color emission acidichromism, viscosity-dependent fluorescence, and biological imaging. [Display omitted] • Five DSE fluorophores IP1-5 based on carbonyl-substituted imidazo[1,2- α ]pyridine have been synthesized and characterized. • IP1-5 exhibited full color solid emission through manipulation of D-A electronic structures and conjugation length. • IP1-5 displayed reversible acidochromism and bioimaging applications with excellent biocompatibility and cell permeability. • IP1-3 showed viscosity-dependent fluorescence with application as potential viscosity sensors. [ABSTRACT FROM AUTHOR]

γ-Glutamyltranspeptidase (GGT) is a cell surface-associated enzyme, which has been proven to be closely related to many diseases. Thus, development of simple and effective GGT-activatable fluorescent probes for early diagnosis of diseases is of great significance. Herein, a series of simple isomeric pyridine-based GGT-activatable fluorescent probes has been successfully designed and synthesized. The preliminary experimental results indicate that Py-GGT-1 has a significant fluorescence response to GGT via a rare fluorescence-off approach. Further fluorescence response experiments, such as the time-/dose-dependent fluorescence change and the selectivity/specificity estimation, reveal that Py-GGT-1 has an excellent ability to monitor endogenous GGT activity. Mechanism studies through HRMS analysis, DFT calculations and molecular docking have theoretically verified the catalytic process between Py-GGT-1 and GGT. To develop its practical application, live-cell imaging and serum-sample analysis were carried out, demonstrating that Py-GGT-1 coud effectively track GGT within cells and organisms. Based its high selectivity and reasonable sensitivity, we expect that the probe will be applied in clinical diagnosis of GGT-related diseases in the future. • We have designed and synthesized a series of simple isomeric pyridine-based probes for GGT detection, which performed a good photophysical property and showed a rapid response to GGT. • Py-GGT-1 was selected as the optimal GGT-activatable probe based on further fluorescence response experiments, such as the time-/dose-dependent fluorescence change and the selectivity/specificity estimation, which revealed that Py-GGT-1 had an excellent ability to monitor endogenous GGT activity. • Mechanism studies through HRMS analysis, DFT calculations and molecular docking theoretically verified its catalytic process between Py-GGT-1 and GGT. • Compared with the reported GGT-activatable probes, our probe shows its simplicity, reliability and rapid response for in vitro monitoring GGT activity with high selectivity and reasonable sensitivity, which is expected to be applied in clinical diagnosis of GGT-related diseases in the future. [ABSTRACT FROM AUTHOR]

We have installed cycloalkylamino auxochromes on naphthalimide (5a - 5e) and nitrobenzoxadiazole (6a - 6e) dyes. Their photophysical characterization revealed that the cyclobutylamino auxochrome in both dyes (5b and 6b) demonstrated high quantum yield and fluorescence brightness compared to their azetidine counterparts (5 and 6) in aqueous solution. The computational studies were performed to substantiate the experimental photophysical results. Cytotoxicity assay in breast adenocarcinoma (MDA-MB-231) and non-cancerous human embryonic kidney 293 (HEK-293) cells indicated significant biocompatibility of cyclobutylamino auxochrome. Moreover, cellular imaging and photostability experiments demonstrated the practical application of cycloalkylamino auxochromes. [Display omitted] • Cycloalkylamine substituted naphthalimides (5a-5e) and 4-nitrobenzoxadiazole (6a-6e) were synthesized and compared with azetidine substituted counterparts (5 and 6) for their fluorescent properties. • Cyclobutylaminated derivatives of naphthalimides and 4-nitrobenzoxadiazole (5b and 6b) show enhanced quantum yields and fluorescence brightness in comparison to their azetidine counterparts (5 and 6). • Compounds 5b and 6b show better biocompatibility and excellent cell penetration in MDA-MB-231 breast cancer cells than their reference standards (5 and 6). [ABSTRACT FROM AUTHOR]

A novel cancer cell and lysosome dual-targeted photosensitizer (PS) termed by BMP was developed for fluorescence imaging and photodynamic therapy (PDT). BMP consists of a porphyrin(Zn) core with appropriate singlet-triplet state distribution enables it to function as an imaging agent as well as a PS, a biotin moiety that can target cancer cells, and a morpholine group specific to lysosomes. Intracellular experiments demonstrated that the dual-targeted photosensitizer BMP could preferably accumulate in cancer cells and subsequently locate within lysosome organelles. Upon irradiation, BMP could generate red fluorescence emission (Φ em = 6.3%) and singlet oxygen (1O 2 , Φ Δ = 55%) for the dual functionality of cell imaging and PDT, respectively. Notably, BMP exhibited much higher photocytotoxicity toward cancer cells (A549 cells) compared to normal cells (BEAS-2B cells). Importantly, 1O 2 produced by BMP induced oxidative damage of lysosomes, and subsequently triggered cell death of A549 cells, as evidenced by the loss of morphological integrity and cell rupture. A cancer cell and lysosome dual-targeted photosensitizer BMP was designed to generate red emission and singlet oxygen (1O 2) simultaneously, which were utilized successfully for dual-targeted fluorescence imaging and photodynamic therapy. [Display omitted] • A dual-targeted photosensitizer was designed and synthesized by modularization. • Biotin acted as a targeting ligand for cancer cells, and morpholine was selected as the lysosome-specific group. • Red fluorescence and singlet oxygen generation were achieved for fluorescence imaging and PDT of cancer cells simultaneously. [ABSTRACT FROM AUTHOR]

A series of hydroxy thiophene-conjugated benzothiazole derivatives (HTB s) was prepared to investigate their fluorescence emission behaviors and capability to selectively stain subcellular organelles for fluorescence imaging. The HTB derivatives exhibited excited-state intramolecular proton transfer (ESIPT) and intramolecular charge transfer (ICT) behaviors, according to their molecular structure. Subtle changes in the molecular structure of the HTB influenced its response to changes in the surrounding environment, such as the solvent polarity and/or pH. In vitro cellular imaging experiments revealed that HTB A (5-(benzo[d]thiazol-2-yl)-[2,2′-bithiophen]-4-ol) could selectively stain mitochondria. In contrast, HTB B -CO 2 Et (ethyl 5'-(benzo[d]thiazol-2-yl)-3′-hydroxy-[2,2′-bithiophene]-5-carboxylate), which contains a regioisomeric hydroxy thiophene unit with an electron-withdrawing ethyl ester group, showed the capability to stain lipid droplets (LDs) in living cells. When the hydroxyl group in HTB B -CO 2 Et was protected with a benzyl group, effective staining of LDs in live cells was achieved. Thus, we successfully obtained an effective fluorescent probe. Collectively, the results indicated that small structural changes resulted in substantial changes in the intracellular localization and in vitro imaging ability of the prepared compounds. [Display omitted] • Hydroxy thiophene-conjugated benzothiazole derivatives (HTB s) were synthesized. • HTB s exhibited polarity-dependent bright emission due to ESIPT and ICT. • The structural change of HTB s enabled selective staining of mitochondria and lipid droplets. [ABSTRACT FROM AUTHOR]

Developing fluoran dyes for fluorescent material is significant but challenging because they are notorious for terrible luminescent efficiency. In this manuscript, two fluoran dyes (F3 and F4) were synthesized by the introduction of thiazole and indazole into the fluoran skeleton, which showed colored and fluorescent spirolactone opening form in a wide pH range (F3 : 1–10, F4 : 1–13). In addition, the absorption and emission spectra of methyl esterification products F3Me and F4Me showed large Stokes shifts (over 75 nm) in water and achieved an improved fluorescence quantum yield of 30.1% in CHCl 3. Based on the dye F4Me, a new fluorescent probe F4HP was developed, which showed high selectivity and high sensitivity (LOD of 2.0 nM) to copper ions in H 2 O/CH 3 CN (v/v, 3/2) system. Moreover, the sensing experiment was allowed in the pH range of 4.0–7.5. Furthermore, the F4HP exhibits suitable cell cytotoxicity and can be applied for imaging intracellular copper ions by confocal fluorescence imaging technology. Thiazole and indazole functionalized fluoran dyes were prepared with improved fluorescence and application in the construction of a novel copper-selective and sensitive fluorescent probe. [Display omitted] • Two modified fluoran dyes were prepared with stable fluorescence in water. • F4Me achieved a fluorescence quantum yield of 30.1% in CHCl 3. • A novel probe F4HP for Cu2+ was prepared with high selectivity and sensitivity. • F4HP could be employed as a tool for imaging intracellular Cu2+. [ABSTRACT FROM AUTHOR]

Five BODIPY derivatives containing different number of styryl units were designed and synthesized based on the Knoevenagel reactions. All compounds were characterized by NMR and HRMS. The single crystal structures of compounds 1 and 3 – 5 were confirmed by X-ray crystallography. The photophysical and electrochemical properties of these dyes were also investigated by UV/Vis spectroscopy, fluorescence spectroscopy, and cyclic voltammetry. Our study indicates that the optical and electronic properties of the BODIPY derivatives could be easily tuned by the introduction of a various number of styryl units. Their absorption and emission spectra become gradually bathochromically shifted from the red region to the near-infrared region. Their first reduction and first oxidation potential (HOMO-LUMO gap) changes from 2.45 to 1.62 V. The structure-optical property relationships of these compounds are also systematically studied. Furthermore, cellular uptake experiments suggest that compounds 1 – 3 are membrane permeable and promising fluorophores for bio-labeling/imaging applications. • Five BODIPY derivatives containing different number of styryl units were synthesized. • The structure-optical property relationships are systematically studied. • Compounds 1 – 3 show excellent cell membrane permeability, and can be utilized as cell fluorescence imaging. [ABSTRACT FROM AUTHOR]

The deficiency and excess of Fe3+ will lead to biological disorders and even many diseases. So, measuring the levels of Fe3+ in human body has drawn great attentions for health monitoring. Fluorescence method has been broadly applied because of high sensitivity, real-time detection and intracellular imaging. In this work, a new lipidic conjugated polymer, poly[3-{2-[2,5-Bis-(2-ethyl-hexyloxy)-4-propenyl-phenyl]-vinyl}-9-butyl-6-methyl-9H-carbazole] (PBMC), has been synthesized and used to prepare the conjugated polymer nanoparticles (CPNs-PBMC) by coprecipitation with poly (styrene- co -maleic anhydride) (PSMA). The CPNs-PBMC exhibited large Stokes shift (141 nm), small average diameter (43.96 nm), low toxicity and excellent photostability. Meanwhile, the CPNs-PBMC was highly sensitive to Fe3+ and has a lower detection limit of 0.63 nmol/L. The sensing mechanism was based on aggregation-induced fluorescence quenching of CPNs-PBMC in the presence of Fe3+ because of chelation and electrostatic interaction. Furthermore, the critical micelle concentration was measured by fluorescence method. More interestingly, the fluorescence of CPNs-PBMC could be circularly quenched and recovered using Fe3+ and EDTA, which may supply a possible control by logic gate. Furthermore, the fluorescence imaging showed that CPNs-PBMC could detect Fe3+ in living cells. A new lipidic conjugated polymer (PBMC) has been synthesized and used to prepare the conjugated polymer nanoparticles (CPNs-PBMC) by coprecipitation with PSMA. The CPNs-PBMC exhibited large Stokes shift (141 nm), small average diameter (43.96 nm), low toxicity and excellent photostability, and could detect Fe3+ with high sensitivity (LOD = 0.63 nmol/L) based on aggregation-induced fluorescence quenching (AIFQ). Moreover, the fluorescence of CPNs-PBMC could be controlled by logic gate using Fe3+ and EDTA. Finally, CPNs-PBMC was successfully applied to Fe3+ detection in living cells by confocal imaging. Image 1 • The CPNs-PBMC exhibited large Stokes shift (141 nm). • The CPNs-PBMC was highly sensitive to Fe3+ and has a lower detection limit of 0.63 nmol/L. • The CPNs-PBMC detected successfully Fe3+ in living cell. • The fluorescence of CPNs-PBMC could be controlled by logic gate using Fe3+ and EDTA. [ABSTRACT FROM AUTHOR]

In this study, a pH-sensitive fluorescent probe was created through the host-guest assembly of an amphiphilic hydroxyphenyl benzotriazole derivative (HBT-11) and cucurbit[7]uril (CB7). The fluorescence of HBT-11 is highly dependent on the molar ratio (r) of CB7 to HBT-11. If r < 1, the peak positions remain unchanged while the intensity increases with r. If r > 1, the emission peaks shift to longer wavelengths. The complexation also results in a shift in the p K a of HBT-11. The 1:1 mixture of CB7 and HBT-11 has a p K a close to neutral pH. The supramolecular probe allows for discrimination of malignant A549 and benign HEK 293T cells owing to a pronounced 8-fold light-up effect in malignant A549 cells attributed to the pH-responsive fluorescence. Given that the selective light-up mechanism is based on the pH-sensitive fluorescence of the supramolecular probe, this approach is expected to be applicable to other cancer cells. [Display omitted] • A pH-sensitive supramolecular fluorescence probe was constructed. • The fluorescent intensity of the probe was greatly enhanced as pH < p K a. • The probe was applied to discriminate malignant and benign cells. [ABSTRACT FROM AUTHOR]

Fluorescent probes sensitive to microenvironments have constantly been attractive, due to their significant benefits in monitoring changes in the pathophysiological microenvironment and their use in the early detection of associated disorders. In this work, we explored three new molecular rotors that could be potential candidates for detecting lipid droplets (LDs) in cancer cells based on coumarin derivatives connected with electron-donating polycyclic units including, tetraphenylethylene (LD-TPE), pyrene (LD-PYR), and 4,5-diphenylimidazole (LD-DIP). Gratifyingly, LD-PYR showed exceptional polarity and viscosity sensitivity and demonstrated bright fluorescence in highly viscous environments due to the suppression of the twisted intramolecular charge transfer (TICT) phenomenon and intramolecular rotation. Moreover, microenvironment-guided specific LD bioimaging by LD-PYR exhibited a reasonable ability to distinguish between cancer and noncancer cells. These data suggested that LD-PYR has interesting clinical diagnostic and microenvironment-related biological applications. [Display omitted] • Highly polarity and viscosity-sensitive fluorescence probes have been introduced. • LD-PYR probe shows bright fluorescence in a lipophilic environment due to TICT suppression. • LD-PYR demonstrates good biocompatibility in both cancer cell and normal cell lines. • LD-PYR can selectively image lipid droplet in cancer cells. [ABSTRACT FROM AUTHOR]

Abstract Cysteine (Cys) plays a vital role in many physiological processes, and also is closely related to various diseases, thus the development of novel high selectivity and sensitivity fluorescent probes for in situ monitoring of biothiol (Cys) is crucial. Herein, we present a fluorogenic method to detect Cys in vitro and live cells based on fluorescent protein chromophores, which have been modulated by chemical reaction. Probe (RFP) is a fluorescence turn on probe with red emission wavelength and large Stokes shift (127 nm). This Michael-addition reaction-based probe exhibits low detection limit (18.7 μM), fast response time, and low cytotoxicity. RFP can differentiate the Cys and Hcy, using the difference of reaction time between probe and Cys or Hcy. Together, this probe exhibited excellent cell permeability, and can be successfully applied to detect the endogenous Cys in living cells. Highlights • Provide a fluorogenic method to detect Cys based on fluorescent protein chromophores. • Realize the red emission and large Stokes shift using chemical modulation method. • Differentiate the Cys and Hcy using the difference of reaction time. • Detection endogenous or exogenous Cys in living cells and served as bioimaging reagent. [ABSTRACT FROM AUTHOR]

Abstract The mixing of donor and acceptor molecules in fluorescent nanoparticles offers an effective route to adjusting the emission properties of the nanoparticles. In this work, the electron donor 1,1-bis[(di-4-tolylamino)phenyl]cyclohexane (TAPC) and the electron acceptor 2,4-bis[4-(diphenylphosphinyl)phenyl]-6-[4-(hexyloxy)phenyl]-1,3,5-triazine (BPOTZ-OR) were coprecipitated to form fluorescent nanoparticles. Efficient exciplex emission occurred in the nanoparticles owing to the good electron affinity and appropriate stacking distance between TAPC and BPOTZ-OR. The exciplex emission and monomer emission were easily tuned by simply changing the BPOTZ-OR/TAPC molar ratio. An appropriate combination produced white-light emission. The large red-shift of the emission from the exciplex, good stability under physiological conditions, and low toxicity suggest potential for this kind of nanoparticle to be an effective fluorescent probe for cell imaging. Graphical abstract Image 1 Highlights • Exciplex emission nanoparticles upon appropriate stacking distance were prepared. • Multicolor emission can be obtained by adjusting the donor-acceptor molar ratio. • The exciplex nanoparticles showed excellent performance in live cell imaging. [ABSTRACT FROM AUTHOR]

Abstract Three novel boron-dipyrromethene (BODIPY) dyes bearing borneol moieties have been designed, synthesized and characterized. The single-crystal structure of the compound 3 was also elucidated for the first time. Their photophysical properties and confocal fluorescence images were investigated by the optical spectroscopy and Confocal fluorescence microscopy. The results indicate that the ompounds 2 – 3 take on high fluorescence quantum yield and cell membrane permeability, which can be utilized as fluorescent visualizers for cell and lysosome fluorescence imaging. Highlights • Three novel boron-dipyrromethene dyes bearing borneol moieties take on excellent cell membrane permeability. • The compounds 2 and 3 show high fluorescence quantum yield. • The dyes 2 and 3 can be utilized as fluorescent visualizers for cell and lysosome fluorescence imaging. [ABSTRACT FROM AUTHOR]

Abstract Encapsulating fluorogens into polymeric nanoparticles is proven an effective method to shield the fluorogens from the outer environment and improve the biocompatibility as well. Conventionally, the fluorogens are firstly conjugated to the monomers and then polymerized into macromolecules, where tedious molecular design and synthesis was unavoidable. Herein, we present a facile method to prepare the fluorogen-functionalized polymer, and then use the polymer as build blocks to fabricate nano-probes aiming at cell-imaging. Unlike the conventional ways, we prepared a homopolymer with active esters on the repeating units and used the polymer as matrix to graft fluorogens and hydrophilic groups. Note that the fluorogen and hydrophilic groups selected in our study were tetraphenylethylene (TPE) and polyethylene glycol (PEG), respectively. The resulting amphiphilic random copolymer self-assembled into spherical nanoparticles with size around 225 nm in aqueous solution. With comparable amount of TPE moieties, the polymeric nanoparticles demonstrated much stronger emission than the nanoparticles formed by small molecules of TPE derivatives. The polymeric nanoparticles showed very good stability and biocompatibility, and were employed to label Hela cells and gave high-contrast fluorescent images. We anticipate that the methodology presented in this study might be developed into a general avenue to encapsulating fluorogens into nanoparticles. Graphical abstract Image 1 Highlights • Post-polymerization modification was employed to prepare amphiphilic copolymers. • The copolymer contains TPE and PEG groups on the side chain. • The nanoparticles formed by the copolymers showed strong fluorescent emission. • The nanoparticles were applied to label Hela cells with high-contrast images. [ABSTRACT FROM AUTHOR]

New fluorescent dyes derivatized on a classical thiazole orange framework are able to show unexpectedly strong interaction signal and unusual binding selectivity with different structures of nucleic acid, particularly when bound with double-stranded DNA or G-quadruplex DNA. The present study reveals that these small binding ligands simply bearing an additional amino side group on its parent molecule of thiazole orange have almost no background fluorescence in solution. Conversely, they are able to produce an extremely strong yellow emission signal upon interaction with targeting nucleic acids in live cells. The induced fluorescence intensity was approximately 10–15 times stronger than that of thiazole orange. The dyes are therefore excellent fluorescent stains for bio-sensing and bio-imaging applications. It is particularly suitable for fluorescence microscopy experiments requiring very low working concentration (0.25 μM or less) targeting nucleic acids. This was demonstrated using pu27 G-quadruplex DNA, which has a low limit of detection (LOD = 3–4 nM) while thiazole orange was much higher (LOD = 48.7 nM) under the same conditions. In addition, it was found that structural modification on the quinolinium scaffold of thiazole orange was less effective than modification on the benzothiazole moiety. The findings of the present study provide important information for structural advancement of small molecules based on the widely used thiazole orange skeleton, resulting in analogues that are able to achieve higher sensitivity and selectivity for targeting at a specific class of nucleic acids. Computational docking studies were also conducted to illustrate the interaction behaviors of the dyes with different DNA structures. [ABSTRACT FROM AUTHOR]

A series of new dyes based on the fluorescent imidazo[1,5- a ]pyridine moiety has been designed and synthesized specifically for fluorescence cell imaging application. The obtained molecules contain a carboxylic functional group inserted to increase the water solubility and to provide an effective conjugation site. Their structural and optical properties have been deeply investigated and compared with theoretical calculations. The suitability of the products as fluorescent labels for cell imaging applications has been investigated by laser scanning confocal microscopy, both in vivo on Arabidopsis thaliana seedlings and in vitro , on mouse fibroblast cells. The compounds displayed good permeability to the plant cell wall and plasma membrane, they were efficiently internalized in the inner plant tissues, and retained a strong fluorescence in aqueous media. [ABSTRACT FROM AUTHOR]

A new amphiphilic polynorbornene-based copolymer P1 was designed and synthesized successfully by ring-opening metathesis polymerization (ROMP) of polyethylene glycol (PEG) containing monomer NB-PEG and ferreocene-anchored monomer NB-Fc. The copolymer P1 can bind with anionic uranine dye (UD) through multiple interactions to form no fluorescent P1 / UD nano-structure ensemble in aqueous solution. The P1 / UD ensemble can be used as indicator displacement assay (IDA) for ATP detection with a high sensitivity and selectivity. Upon the addition of ATP, the fluorescence is significant enhanced for displacement of UD from P1 / UD ensemble. The LOD value of P1 / UD ensemble toward ATP is as low as 35.9 nM. The P1 / UD ensemble exhibits an excellent photo-stability and biocompatibility, and has been successfully used for imaging ATP in living cells. [Display omitted] • A new amphiphilic polynorbornene-based copolymer P1 was designed and synthesized. • P1 can bind with UD to form P1 / UD nano-structure ensemble in aqueous solution. • P1 / UD ensemble can detect ATP with a high sensitivity and selectivity by IDA. • P1 / UD ensemble exhibits an excellent photo-stability and biocompatibility. • P1 / UD ensemble has been successfully used for imaging ATP in living cells. [ABSTRACT FROM AUTHOR]

The abnormal expression of cytochrome P450 2J2 (CYP2J2) is closely related to the proliferation of human cancer cells. In this study, a red-emitting probe with an aggregation-induced emission (AIE) effect for the quantification of CYP2J2 was developed by modifying the typical AIE fluorescent group tetraphenylethylene (TPE) through two-step synthesis. Upon addition of CYP2J2, the probe underwent O-demethylation and spontaneously 1,6-elimination reactions of p-hydroxybenzyl that allowed it to alter its photophysical properties, thus realizing light-up detection of CYP2J2 with extremely large Stokes shift (236 nm), excellent sensitivity and selectivity, low detection limit (1.09 nM). Moreover, this new AIE-active probe with good biocompatibility was admirably employed to tracking endogenous CYP2J2 in living cells. • An AIE-based fluorescent probe (TPE-Bn) was designed to detect CYP2J2. • This probe showed significant Stokes shift (236 nm), good photostability, excellent sensitivity and selectivity, and low cytotoxicity. • This probe can be used to visualize endogenous CYP2J2 in living cells and tissues. [ABSTRACT FROM AUTHOR]

A new simple aminohydantoin-based fluorescent chemosensor 1 was designed for sequential detection of Zn 2+ and pyrophosphate in a near-perfect aqueous solution. 1 exhibited significant fluorescence intensity in the presence of Zn 2+ , and the resulting 1 -Zn 2+ complex showed subsequently the fluorescent quenching with pyrophosphate. The detection limit (0.32 μM) of 1 for Zn 2+ was far lower than the guideline of World Health Organization in drinking water. 1 was used to determine Zn 2+ concentration in various water samples. In addition, chemosensor 1 could be applied to sequentially detect Zn 2+ and pyrophosphate in living cells and zebrafish. The sensing mechanism of Zn 2+ by 1 was proposed to be an intramolecular charge transfer with theoretical calculations. [ABSTRACT FROM AUTHOR]

Herein, a new water soluble Ca 2+ fluorescence chemosensor based on aggregation-induced emission (AIE) characteristics has been developed, combining the AIE effect of tetraphenylethylene (TPE) and the complexation capability of bidentate pyridine carboxylate. The bidentate pyridine carboxylate group provides the chemosensor with good water-solubility which is important for detection in biological systems. This chemosensor L showed high selectivity for Ca 2+ by a turn-on response in almost pure aqueous solution with a detection limit of 51.2 nM. L can be used as a recyclable Ca 2+ fluorescent chemosensor in the presence of EDTA. Moreover, the chemosensor L was successfully applied to imaging detection and real-time monitoring of Ca 2+ in living cells with low toxicity and good membrane permeability. [ABSTRACT FROM AUTHOR]

Biothiols, such as cysteine (Cys), homocysteine (Hcy), and glutathione (GSH), play essential roles in many physiological and pathological processes. In this work, three porphyrin derivatives, XQ1 , XQ2 and XQ3 , were synthesized by combining the porphyrin framework with nitroethylene, bis(methoxycarbonyl)ethylene and dicyanoethylene moieties, respectively. XQ1 was almost nonfluorescent, which could be utilized as a good starting point for developing fluorescence turn-on probes. Thus, XQ1 exhibits fast fluorescence enhancement and high selectivity towards the biothiols based on the Michael addition mechanism. It also exhibits high sensitivity towards the biothiols with the detection limits of 0.65–1.1 μM. In addition, XQ1 was successfully applied to cell imaging in living A549 cells for visualizing the biothiols. The results compose a good example of designing porphyrin derivatives for detecting biothiols, with the advantages of dramatic fluorescence enhancement in the NIR wavelength range, which exhibits good cell membrane permeability and practicability in detecting both exogenous and endogenous biothiols. [ABSTRACT FROM AUTHOR]

The self-assembly of organic molecules is versatile to prepare various nanostructures. In this work, a new fluorescent molecules containing triple-BODIPY ( TBDP ) were synthesized, which can self-assemble into stable nanoparticles ( TBDP-NPs ) by nanoprecipitation procedure. The byproducts containing dual-BODIPY units also could form nanoparticles, which possess relatively poor stability in aqueous media. Interestingly, the fluorescent nanoparticles emit different fluorescence at 566 nm and 683 nm under excitation of 500 nm, and the emission at 683 nm can be used as sensor for validating the self-assembly behaviors. The TBDP-NPs excellent cytocompatibliy, and could be internalized by cancer cells for living cell imaging. This work highlights the great potential of self-assembling of organic molecules for functional nanomaterials. [ABSTRACT FROM AUTHOR]

GSH is an important biological thiol which involves many biological processes, and also an biomarker for cancer. So it's urgent to develop fluorescent probes with excellent sensitivity and high selectivity for GSH detection. Herein, we develop a new GSH-responsive fluorescent probe TPP-Naph-SS-Fc based on PET (photoinduced electron transfer) mechanism. TPP-Naph-SS-Fc contains naphthalimide fluorephore, the ferrocene quencher, the disulfide cleavage bond and the triphenylphosphine mitochondrial localizer. It shows a fluorescence turn-on response toward GSH for cleavage the disulfide bond, which result in the blocking of PET process. Especially, this probe can localize in mitochondria and make real-time imaging of GSH, also demonstrate the ability to distinguish between cancerous and normal cells. A naphthalimide-based fluorescent probe with mitochondria targeting for GSH sensing and cancer cell recognition based on PET mechanism have been reported. [Display omitted] • A novel naphthalimide-based fluorescent probe TPP-Naph-SS-Fc was prepared based on PET mechanism. • The probe shows fluorescence turn-on response toward GSH. • It has the excellent mitochondria targeting ability. • It has been applied in cellular GSH imaging and cancer cells recognition. [ABSTRACT FROM AUTHOR]

The novel V-shaped donor-π-acceptor-π-donor compounds bearing an aldehyde group (1Pip , 2EtO , and 3TEG) were designed, synthesized, and evaluated as the two-photon excited fluorescence probes for the selective detection of cysteine (Cys). Their structures were fully characterized by 1H NMR, 13C NMR, FT-IR, and HRMS. The optical properties of the target compounds in various solvents were studied in details and the time-dependent density functional theory calculations were performed to shed light on their electronic structures. It is found that all of them exhibit large Stokes shifts (6331-10047 cm−1). 1Pip and 3TEG are capable of detecting Cys with high selectivity, good anti-interference ability, and favorable two-photon absorption performance. The limits of detection were determined to be equal to 0.15 μM for 1Pip and 0.73 μM for 3TEG. The possible recognition mechanism was also validated by 1H NMR and HRMS. One- and two-photon fluorescence imaging experiments indicate that 3TEG shows more satisfactory cellular membrane permeability than 1Pip , and it can successfully visualize the endogenous and exogenous Cys in living cells. These results imply that 3TEG has potential as a two-photon fluorescence probe for detecting Cys in biological samples. [Display omitted] • Three novel D-π-A-π-D type two-photon absorption compounds were developed to detect Cys. • 3TEG shows high selectivity to Cys, favorable two-photon absorption property, large Stokes shifts, and good biocompatibility. • 3TEG has been successfully utilized to image endogenous and exogenous Cys in living cells. [ABSTRACT FROM AUTHOR]

A series of boronic acid derived salicylidenehydrazinopyridine complexes have been synthesized from the condensation of 2-hydrazinopyridine or 2-hydrazinoquinoline and salicylaldehyde then followed by complexation with various boronic acids. Their X-ray structures demonstrate that the boron atoms adopt a tetrahedral geometry and the aryl substituents from arylboric acids along the vertical axis gave the molecule stereotactic structure and induced molecular chirality. These dyes have good solubility on organic solvents due to the nonplanar curved structure and the presence of axial-substituted groups that provide steric protection. They have strong visible-light absorption, weak emission and large Stoke shifts in organic solvents. Interestingly, molecular aggregates of these new boron complexes experienced the transformation from H -type aggregation to J- type aggregation and exhibited strong aggregation-induced emission (AIE) activities. These novel AIE dyes showed great potential as bioimaging dyes, and two complexes were mainly distributed in lipid droplets of cells in colocalization experiments. [Display omitted] • New boron complexed fluorophore (BOSPY) has been developed from various arylboric acids. • Molecular chirality of these dyes after boron complexation was confirmed by X-ray structures. • These dyes exhibit strong aggregation-induced emission (AIE). • These AIE dyes are suitable for fluorescence imaging and two dyes can specifically localize in lipid droplets of cells. [ABSTRACT FROM AUTHOR]

In this work, a colormetric fluorescent probe named NMH, which exhibited aggregation-induced emission (AIE) characteristic in water/EtOH binary solvent was developed based on 2-hydrazinobenzothiazole and 6-methoxy-2-acetonaphthone for sensing hypochlorous acid (HClO) with high selectivity and sensitivity (detection limit: 1.7 nM). Also, NMH had a strong anti-interference effect and a fluorescence color change in the solution which can be seen by the"naked eye". Moreover, NMH could be applied to detect ClO− in tap water and test paper. In addition, cell imaging experiments showed that probe NMH could detect endogenous and exogenous ClO− in A549 cells successfully. In this work, probe NMH, which exhibited aggregation-induced emission (AIE) characteristic in water/EtOH binary solvent was developed and could be applied to detect ClO− with colormetric response in tap water, test paper and living cells. [Display omitted] • A selective fluorescent probe NMH with aggregation-induced emission characteristic was developed by one step reaction. • The probe NMH could be widely used as a "naked eye" probe for detecting ClO− by the color changes from purple to blue. • The probe NMH could detect endogenous and exogenous ClO− in A549 cells successfully. [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]

A new type of the red-emitting benzo[ a ]phenoxazine-based dyes, dipolar analogues of Meldola's Blue, are synthesized by condensation of p- nitrosoanilines or p- nitrosophenol with 7-(alkylamino)naphthalen-2-ol in good yields. Their photophysical properties are characterized by the donor substituents introduced, offering dyes of lavender violet, blue, and pink colors. These dyes exhibit high absorptivity, marginal-to-good optical brightness, good photostability, and show large Stokes shifts in aqueous solution. One of the dyes emits bright red fluorescence inside cells, as observed by confocal laser scanning microscopy (CLSM). The new dyes thus have potential to be used for staining purposes including cellular imaging. [ABSTRACT FROM AUTHOR]

This study reports a benzothiazole-based fluorescent probe EPS-HS for real-time detection of H 2 S. The probe is characterized in a large red-shift, good selectivity, high sensitivity and favorable biocompatibility. We measured the detection limit of EPS-HS in PBS buffer and fetal bovine serum. Moreover, in HT22 living cell imaging studies, EPS-HS showed good cell permeability and H 2 S could be detected within the cells. Furthermore, in situ visualization of H 2 S was performed on the hippocampal slices of normal mice with EPS-HS. We were also able to estimate the concentration of sulfide in mouse hippocampus tissues. The probe will be applied for better treatment of neurological deficits caused by damage to the hippocampus. [ABSTRACT FROM AUTHOR]

It is highly demanded and challenging to develop small-molecular fluorescent sensors for the ratiometric detection of pH fluctuation. A ratiometric fluorescent pH sensor was constructed by integrating a pH-sensitive fluorophore with a pH-insensitive hemicyanine group. Its linear and reversible ratiometric fluorescent response from pH 7.0 to 8.8 and 6.0 to 9.0 respectively makes this sensor suitable for the practical tracking of pH fluctuation in live cells. With this sensor, stimulated pH fluctuation has been successfully tracked in a ratiometric manner via fluorescence imaging with low dark toxicity. [ABSTRACT FROM AUTHOR]

An NBD-derived fluorescent sensor termed CdTS was reported to sense Cd 2+ with very high binding selectivity and significant fluorescence turn-on signal selectivity (65 fold enhancement). The amide/di-2-picolylamine receptor binds Cd 2+ in an imidic acid tautomeric form, but binds most of other metal ions in an amide tautomeric form. The transformable ability makes CdTS have the specific selectivity for Cd 2+ . Additionally, CdTS can fluoresently and colorimetricly recognize Cd 2+ across a wide pH range from 4.5 to 11.5. Finally, we applied CdTS to detect Cd 2+ in living cells. [ABSTRACT FROM AUTHOR]

This paper reports a near-infrared chemosensor for phosphate ions (Pi) based on Pi-controlled fluorescence off-on switching mechanism. The Pi sensor displayed colorimetric responses towards Pi with a distinct color change from green to yellow in aqueous media. Apyrase, a hydrolytic enzyme, was used to accelerate the endogenous Pi production for evaluating in vivo fluorescent sensing ability of the new cyanine based probe ( 1 ). In addition, the present study demonstrated potential of the newly developed chemosensor in bioimaging by performing experiments in Chinese hamster ovary (CHO) cells both in vitro and in vivo. [ABSTRACT FROM AUTHOR]

Thiophenols, a class of toxic and polluting compounds, are widely used in industrial production. Meanwhile, some aliphatic thiols play important roles in living organisms. Therefore, the development of probes for specific thiophenol detection is of great importance. Herein, a novel highly sensitive and selective ‘off-on’ fluorescent probe for detecting thiophenols has been developed by an ICT mechanism through a rational design. The probe displays a large Stokes shift (140 nm) and 60-fold fluorescence intensity enhancement. More importantly, the probe features a rapid signal response time (within 100 s), a good linearity range and the detection limit is as low as 13 nM. In addition, the ability of the probe to detect thiophenols in living cells (HepG2 cells) via an enhancement of the fluorescence has also been demonstrated. [ABSTRACT FROM AUTHOR]

A neutral pH fluorescent probe (Rh-Met) based on rhodamine spirolactam is firstly developed according to the modulation strategy of hydrogen bonds on pKa values. The pKa value of Rh-Met was 6.81 (±0.06) and higher than that of other rhodamine spirolactams known. Rh-Met showed a 240-fold enhancement of fluorescence intensity at 585 nm with attenuation of pH values from 9.7 to 3.5. In addition, Rh-Met displayed an excellent selectivity and reversible response to hydrogen ion. And it was successfully employed for imaging endocellular hydrogen ion in mitochondria and lipid droplets. These results suggested that Rh-Met could be a potential tool to assess pH fluctuation in mitochondria and lipid droplets, and would promote many new opportunities for studying the biological effect of pH in living cells. [ABSTRACT FROM AUTHOR]

Triphenylphosphonium (TPP) cations endow fluorophores with improved hydrophilicities and mitochondria targeting abilities. Evidently, the number of cationic moieties can influence the behavior of fluorophores in different environments. Two water-soluble BODIPY fluorophores, 3TPP and 5TPP , were constructed with three and five TPP groups, respectively, in their structure. Both showed maximum absorption and emission at 640–700 nm wavelengths; however, 5TPP showed a fluorescence quantum yield 10 times higher than that of 3TPP in an aqueous medium, highlighting the beneficial effect of two additional TPP groups on the photophysical properties. While both fluorophores showed excellent stabilities and mitochondrial imaging abilities with low cytotoxicities in HeLa and MCF-7 cells, 5TPP permeated into the mitochondria better than 3TPP. Interestingly, 5TPP demonstrated a 90-fold increase in "turn-on" fluorescence in the presence of bovine serum albumin (BSA) in relation to that of four other proteins (i.e., lysozyme, esterase, transferrin, and fibrinogen). Notably, the fluorescence intensity of 5TPP increased with increasing BSA concentration. The present work is the first report on BODIPY sensors with multiple bulky cationic moieties and provides insights on the applicability of 5TPP as a novel biomaterial for mitochondrion tracking and light-up fluorescence protein sensing. • BODIPY-based fluorophores, 3TPP and 5TPP , were conjugated with three and five (triphenylphosphonium) TPP groups, respectively. • Both fluorophores showed excellent photostabilities and mitochondrial imaging abilities with low cytotoxicities in HeLa and MCF-7 cells. • 5TPP exhibited a 90-fold increase in "turn-on" fluorescence in the presence of bovine serum albumin (BSA) with respect to that of four other proteins (i.e., lysozyme, esterase, transferrin, and fibrinogen). [ABSTRACT FROM AUTHOR]

HClO is recognized as an indicator for phagocytosis and inflammatory response. Excess HClO ruptures lysosomes and leads to cell apoptosis, which has been proposed as a cure for cancer treatment. As a consequence, the real-time and in situ cell imaging for HClO is highly appealed in the field of anticancer pharmacy. In this work, a series of silane-modified rhodamine fluorescers with various functional groups were designed, hoping to find a fluorescer with near IR emission for bio-imaging in live cells, along with unique sensing response towards ClO− over competing species. These silane-modified rhodamine fluorescers were carefully characterized, their photophysical parameters and responses towards ClO− and competing species were compared systematically. An optimal probe showed emission quantum yield of 0.26 with emission wavelength at 681 nm. Emission "turn-on" effect was observed, with calibration equation of F = 0.720*[ClO−]2+40.047*[ClO−]+54.982, R2 = 0.999, and the limit of detection (LOD) was calculated as 0.03 μM. Corresponding sensing mechanism was revealed as an HClO-mediated cyclization reaction. Fluorescence imaging for Hela cells and A549 lung cancer cells was performed. The lysosome-targetable feature was confirmed. • A series of silane-modified rhodamine fluorescers with near IR emission for bio-imaging in live cells were reported. • An optimal probe showed emission quantum yield of 0.26 with emission wavelength at 681 nm. • Sensing calibration equation was a non-linear one and the limit of detection (LOD) was calculated as 0.03 μM. • Sensing mechanism was revealed as an HClO-mediated cyclization reaction. [ABSTRACT FROM AUTHOR]

In this paper, oxazolepyridine and coumarin units were combined to prepare cell membrane fluorescent probe (PM-A) through aldol condensation reaction. PM-A had long wavelength emission (665–739 nm), high molar extinction coefficient (around 3.14 × 104 M−1cm−1) and large Stokes shift (150–219 nm). The photo-stability test showed that PM-A had a high relative residual absorption (93%) after 6 h of continuous illumination. In addition, the supramolecular interaction between PM-A and β-cyclodextrin was evaluated and applied to cell imaging. Probe PM-A had no fluorescence in water, but had obvious fluorescence signal in β-cyclodextrin solution. With the addition of β-cyclodextrin (0–800 eq), the fluorescence quantum yield of PM-A increased from 0% to 45%. Laser confocal experiments showed that when only PM-A was added, the probe concentration needed to be 15 μM to image the cell membrane obviously. In sharp contrast, with the help of β-cyclodextrin solution, the concentration of probe PM-A only needed 0.5 μM to quick and high specificity image cell membranes. Moreover, PM-A had high photo-bleaching resistance and long retention time after adding β-cyclodextrin. These excellent properties of PM-A were of great significance to the study of cell membrane. [Display omitted] • A near-infrared fluorescent probe (PM-A) with oxazolepyridine and coumarin units was prepared for the imaging of cell membrane at 15 μM. • The supramolecular interaction between probe PM-A and β-cyclodextrin was evaluated. • Probe PM-A showed rapid and high specificity of cell membrane imaging at the concentration of 0.5 μM with the help of β-cyclodextrin. [ABSTRACT FROM AUTHOR]

Herein, a highly selective and sensitive squaraine dye (F-0) for Cu2+ detection was developed. Upon addition of Cu2+, F-0 could greatly decrease absorption peak accompanying with fluorescent quenching about 170 folds. The detection limit can reach as low as 7.2 nmol/L. F-0 showed excellent water solubility and achieved naked eye detection of Cu2+. A paper strip pre-stained with F-0 solution was fabricated and showed color changed from blue to colorless upon addition of Cu2+. F-0 exhibited highly specific to Cu2+ over other metal ions. Furthermore, on the basic of low cell cytotoxicity, F-0 could be utilized to monitor Cu2+ in living cell and mice via fluorescence imaging. These results showed that F-0 has great potential for a more complex applications. [Display omitted] [ABSTRACT FROM AUTHOR]

Peroxynitrite (ONOO−), as one of the important reactive oxygen/nitrogen species, is associated with many physiological and pathological activities. Therefore, effective detection methods with high sensitivity and rapid response time are essential to reveal its functions. A novel Rhodol-based fluorescent probe RN is constructed and synthesized by introducing of 1,1-dimethylhydrazone as a recognition group. Due to the oxidative breakage of the C N bond by ONOO−, the probe has significant fluorescence enhancement change with excellent detection properties such as rapid response time, high sensitivity and selectivity. Moreover, probe RN show low cytotoxicity and is successfully capable of imaging endogenous and endogenous ONOO− in living cells. These properties indicate that RN has great application potential for imaging of ONOO− in biological systems. [Display omitted] • New Rhodol derivative is designed as fluorescent probe (RN) for monitoring of ONOO−. • Probe RN exhibits turn-on fluorescent change toward ONOO− with high sensitivity and rapid response time (<60s). • Probe RN can be used for monitoring endogenous ONOO− changes in cells. [ABSTRACT FROM AUTHOR]

Organic fluorescent materials have been widely used in various fields including visualization of latent fingerprints and imaging of lysosomes. High-performance organic fluorescent molecules based on simple molecular structures are still limited and highly demanded for high-definition and high-contrast imaging of latent fingerprints and lysosomes. In this work, two organic fluorescent molecules (DANPAN and DANBEN) were developed based on dimethylamino naphthalenyl phenylethene structure. These two molecules have quite different fluorescent properties, and the position of cyano group significantly affects the optical properties of these dimethylamino naphthalenyl phenylethene derivatives. Compound DANPAN shows strong yellow emission in solid state, while compound DANBEN has strong fluorescent emission in organic solutions. In addition to these differences, both compounds have large Stokes shifts and positive solvatochromic properties. Further studies showed that these compounds could be used to display latent fingerprints on various substrate surfaces. The obtained fingerprint images have excellent contrast and high resolution. It is also found that these molecules could specifically stain lysosomes in living cell within short incubation time. This work provides a series of new high-performance organic fluorescent materials with diverse applications. Highly emissive dimethylamino naphthalenyl phenylethene derivatives have been synthesized, which show large Stokes shifts and positive solvatochromic properties. These compounds could be applied for visualization of latent fingerprints and specific localization of lysosomes in living cell imaging. [Display omitted] • Two dimethylamino naphthalenyl phenylethene derivatives are synthesized. • These molecules show large Stokes shifts and positive solvatochromic properties. • These compounds could be applied for visualization of latent fingerprints on various substrate surfaces. • These molecules could be used for specific localization of lysosomes in living cell imaging. [ABSTRACT FROM AUTHOR]

Fluorescence probes have shown great potential in lipid droplets (LDs) imaging, whereas the imaging performance of the present commercial dyes is far from ideal. In addition, there still is lack of an effective strategy for designing LDs specific probes with satisfactory imaging performance. In this work, we have provided a novel method and probes based on donor (D)-acceptor (A) structure with nitrobenzoxadiazole (NBD) as the A unit and benzene derivatives as the D units, which are expected to show strong emission in lipid environment. Four probes (N–B , N–MeB , N–MeOB and N–Me 2 NB) with increasing electron-donating ability were prepared, whose fluorescence-emission changed from aggregation-induced emission (AIE) (N–B and N–MeB) to aggregation-caused quenching (ACQ) (N–MeOB and N–Me 2 NB). Intriguingly, the emission of these probes in oil changed from blue region to red (652 nm) with the increase of electron-donating ability from N–B to N–Me 2 NB , indicating the great emission regulable ability of this strategy. Moreover, these probes could specifically stain the intracellular and tissular LDs, which had shown considerable performance in the studying of LDs spatial distributions in mice and human atherosclerosis plaques. Impressively, N–Me 2 NB with the strongest electron-donating group of N-dimethylaniline showed negligible emission in aqueous solution but remarkable enhanced emission in oil, which could still efficiently stain the intracellular LDs at 200 nM. This novel construction strategy would provide new ideas for preparation of LDs specific probes. • A novel strategy for designing lipid droplets (LDs) specific probe was provided. • The fluorescence emission of N–MeOB and N–Me 2 NB were significantly enhanced in lipid environment. • N–MeOB and N–Me 2 NB showed great LDs imaging performance in cells. • N–MeOB and N–Me 2 NB can detect the LDs distribution in mice and human atherosclerosis plaques. [ABSTRACT FROM AUTHOR]

A new highly selective and sensitive chemosensor 1 for both Al 3+ and F − was designed and synthesized. 1 could detect both Al 3+ and F − with turn-on fluorescence behavior in a nearly perfect aqueous solution. The binding stoichiometry of receptor 1 with Al 3+ and F − was proposed to be 1:1, respectively, based on Job plot, 1 H NMR titration and ESI-mass spectrometry analysis. The detection limits (1.12 μM for Al 3+ and 7.01 μM for F − ) of 1 for Al 3+ and F − were lower than the World Health Organization guidelines (7.41 μM for Al 3+ and 79 μM for F − ) for drinking water. Chemosensor 1 was also successfully applied to living cells for simultaneous detection and quantification of both Al 3+ and F − . Moreover, the sensing mechanisms of 1 toward Al 3+ and F − were explained by theoretical calculations. [ABSTRACT FROM AUTHOR]

We reported here a reversible fluorescent chemosensor CPO for sequential recognition of Cu 2+ and S 2− in aqueous and biological media. This sensor CPO showed highly selective binding towards Cu 2+ along with a fluorescence quenching due to the formation of the corresponding complex (CPO) 2 –Cu 2+ . And this phenomenon could be reversed in the presence of S 2− , resulting in the recovery of its initial intense fluorescence. Moreover, sensor CPO showed a highly sensitive and selective response towards Cu 2+ and S 2− over other metal ions and anions. Particularly, the fluorescence “ON-OFF-ON” responding circle could be repeated over 5 times by the sequential addition of Cu 2+ and S 2− . More important, the actual usage of sensor CPO in the cell imaging study was further demonstrated by confocal fluorescence imaging with living cells. The cellular toxicity and quantification studies in single intact cell were also exploited by the flow cytometry analysis. [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]

In this paper, a cationic amphiphile (denoted by DPP-10) with diketopyrrolopyrrole decorated with methoxylated tetraphenylethylene via a phenyl bridge was designed, synthesized, and applied as a turn-on fluorescence probe for bovine serum albumin (BSA) detection and selective cell imaging. DPP-10 showed very weak fluorescence emission when dispersed in the solution, while its emission was drastically enhanced upon the addition of BSA, which should be attributed to the electrostatic interaction-driven assembly between DPP-10 and BSA. The limit of detection was as low as 0.08 μmol/L, which is lower than that reported for most probes. The fluorescence probe shows good selectivity for BSA among the tested proteins, high photostability, and immunity to the disturbance of ions. DPP-10 with excellent cytocompatibility was applied to HeLa cell imaging, where only the BSA-rich cells showed a strong signal-to-background contrast. A turn-on fluorescence probe was built for the detection of BSA via electrostatic interaction-driven assembly. The BSA-responsive feature was successfully applied in selective cell imaging. [Display omitted] • A turn-on fluorescence probe was designed and synthesized for the detection of BSA. • The probe has a low detection limit, high selectivity and excellent biocompatibility. • The probe was successfully applied to selectively light up BSA-rich HeLa cells. [ABSTRACT FROM AUTHOR]

G-quadruplexes (G4s), DNA or RNA structures formed by guanine-rich sequences, play indispensable regulatory roles in numerous biological processes. Here we develop a Near Infrared (NIR) fluorescence G4 indicator (TAQ) which enables activatable imaging of G4s in live cells. The indicator TAQ is merely emissive in aqueous solution and its fluorescence at 677 nm is remarkably enhanced in the presence of a typical hybrid G4 structure. TAQ broadly interacts with different G4 structures, exhibiting high selectivity toward G4s over single- or double-stranded nucleic acids. It is demonstrated that TAQ affords dynamic fluorescence response to G4 concentrations in the range of 5.0–600 nM with an estimated limit of detection of 0.51 nM. Live cell studies demonstrate that TAQ delivers intense fluorescence signals upon specific interaction with G4 structures. We further employ TAQ to track the dynamics of RNA/DNA G4s in live cells. This NIR fluorescence indicator could provide a valuable tool for interrogating the dynamics of G4 structures in live cells. [Display omitted] • A near infrared (NIR) fluorescence G4 indicator (TAQ) is reported for activatable imaging of G4s in live cells. • The NIR fluorescence probe exhibits high sensitivity and high selectivity toward G4s over other nucleic acids. • The NIR fluorescence probe is successfully introduced to track the dynamic changes of G4s in live cells. [ABSTRACT FROM AUTHOR]

Abstract: A turn-on fluorescent probe DNBS-CSA is reported here with selective detection of thiols over other amino acids. Probe DNBS-CSA possesses the widely-used thiol-selective 2,4-dinitrobenzenesulfonyl (DNBS) group to react with thiols and release the fluorescent salicylaldehyde azine with aggregation-induced emission (AIE) characteristics. The use of AIE dye prevented the sensor from aggregation-induced fluorescence quenching which is challenging for other thiols sensors. Upon the addition of cysteine (Cys) to DNBS-CSA in aqueous solution (10 mM PBS buffer at pH 7.4 containing 30% DMSO), an intense fluorescence enhancement was observed at 558 nm with a large stokes shift of ∼170 nm. Under the optimal condition, the fluorescence intensity linearly increased with the concentration of Cys in the range of 8–18 μM with a correlation coefficient of R 2 = 0.991. The fluorescence enhancement of DNBS-CSA upon addition of Cys on test paper was also observed, enabling DNBS-CSA function as solid materials (such as test papers) for thiols detection. The detection of thiols in serum samples was successfully performed. With good cell permeability, the probe was applied to the imaging of thiols in HEK 293T cells. [Copyright &y& Elsevier]

Abstract: A new fluorescent probe, 3-((4-([2,2′:6′,2″-terpyridin]-4′-yl)phenyl)ethynyl)-7-methoxy-2H-chromen-2-one (ZC-F7) composed of coumarin as the fluorophore and terpyridine as the receptor is designed and synthesized. Based on the intramolecular charge transfer (ICT) effect, the probe exhibits significant variation on emission wavelengths with shifts more than 100 nm after combined with Zn2+, in accordance with the conversion of emission colors from blue to green. Good selectivity and sensitivity of this probe towards Zn2+ can be found even on the ppb level in aqueous solution. The Job's plot test suggests a 1:1 stoichiometry between ZC-F7 and Zn2+. The application of the fluorescence probe in bio-imaging is also demonstrated, proving its potential usage in fields such as environment protection, water treatment and safety inspection. [Copyright &y& Elsevier]

Organic materials with strong solid-state fluorescence and sensitive stimuli responsiveness are highly desired for both fundamental research and practical applications. We report herein an azabenz-annulated perylenediimide (AzaBPDI)-based dye, AzaBP-TPE, which contains tetraphenylethene units in the planar aromatic structure. AzaBP-TPE undergoes typical intramolecular charge transfer, aggregation-induced emission, and mechanochromic fluorescence. In the solid state, AzaBP-TPE emits bright-yellow light with a photoluminescence quantum yield of 27%, and this emission becomes red fluorescence when MCF is induced, by using mechanical force to collapse the crystalline structure. Moreover, bright-yellow fluorescence can be recovered by exposing AzaBP-TPE powder to chloroform vapor. Notably, AzaBP-TPE nanoparticles can penetrate live cells and emit red light and, therefore, can be applied as a functional dye in bio-imaging. [Display omitted] • A novel azabenz-annulated perylenediimide-based dye, AzaBP-TPE was developed. • AzaBP-TPE exhibits typical AIE and reversible MCF in the solid state. • Good biocompatibility indicates AzaBP-TPE a potential functional dye for cell-imaging. [ABSTRACT FROM AUTHOR]

Various aggregation-induced emission luminogen (AIEgen) derivatives based on TPE (tetraphenylethylene) containing the electron-donating moiety (–NMe 2 , –OMe) and bromine (–Br) moiety were prepared, which are key intermediates for tuning the emission wavelength of TPE; Type 1: dimethylamine (NMe 2)-substituted derivatives, Type 2: methoxy (OMe)-substituted derivatives, Type 3: bromine (Br)-substituted derivatives, and Type 4: mixed formulation derivatives. We systematically analyzed the synthesis, AIE properties, photophysical properties, and biological applicability of 16 types of TPE-based AIEgen. We expect that our investigation, especially the donor-substitution effect of TPE, could serve as a guide to developing a new TPE-based AIEgen series as well as fluorescent probes. [Display omitted] • Donor-substitution effect of tetraphenylethylene (TPE) AIEgens was systematically identified. • Synthesis and photophysical property of 16 derivatives of TPE was disclosed. • CLSM imaging of cells using the TPE derivatives was demonstrated. [ABSTRACT FROM AUTHOR]