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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]

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]

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]

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]

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]

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]

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]

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]

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]

Butyrylcholinesterase (BChE) is an esterase expressed by the liver, which is released into the plasma immediately. The activity of BChE in the serum is a sensitive indicator for determining the protein synthesis function of liver cells. Therefore, the development of high-efficiency chemical tools for detecting BChE is in urgent need. In this work, based on the ingenious combination of specific BChE enzymatic reaction, a ratiometric fluorescence probe was established to easily achieve the determination of BChE with high sensitivity with LOD calculated as low as 0.077 μg/mL. This probe also possesses a superior selectivity to BChE without the interference of other biological species even acetylcholinesterase (AChE), which gives it great potential to work for sensing in biological samples. The accurate IC 50 (0.195 mM) of iso-OMPA, a specific inhibitor of BChE, could also be examined, indicating the excellent performance in elucidating inhibitory efficacy. In addition, the probe can be used for fluorescence imaging of BChE activity in living cells as well as animal tissues. These advantages indicate that the probe has important practical value for the monitoring of BChE activity. [Display omitted] • A ratiometric fluorescent probe W1 for the determination of BChE was constructed. • The probe provides high sensitivity for BChE with a LOD calculated as 0.077 μg/mL. • W1 possessed a superior selectivity to BChE without interference of other species. • The accurate IC 50 of iso-OMPA also indicated the excellent sensing performance. • The sensing scheme is workable in biological samples including serum and cells. [ABSTRACT FROM AUTHOR]

Here, a coumarin-based probe 4-chloro-3-formyl-2-oxo-2H-chromen-7-yl acrylate (named CFCA), which performed high efficient and specific recognition for cysteine (Cys), was successfully synthesized and characterized by NMR and MS. The CFCA probe showed colorimetric and "turn-on" fluorescent signals to Cys, and its color changes could be recognized by naked eyes. CFCA responded to Cys with the characteristics of rapid response time (less than 40 s), high selectivity, and excellent anti-interference. Among all kinds of samples, only Cys could significantly enhance the fluorescence intensity of the solution, which was not affected by the presence of other interferences. At the same time, within a certain concentration range, there was a good linear relationship between relative intensity of fluorescence and Cys concentration. The detection limit has been calculated to be as low as 0.33 μM. And the sensing mechanism of CFCA with Cys has been well confirmed by 1H NMR and HR-MS spectra. Moreover, the fluorescence probe CFCA was successfully used for imaging Cys in living cells and processed into test strips for on-site analysis and testing. • A coumarin-based probe CFCA was successfully prepared, synthesized, and applied for Cys detection. • CFCA can perform high efficiency and specificity colorimetric and fluorescent double signal recognition for Cys. • CFCA has been used for imaging Cys in living cells and processed into test strips for on-site analysis and testing. [ABSTRACT FROM AUTHOR]

In this work, we synthesized a novel long-wavelength-emitting fluorophore FQ-OH based on a novel designed hydroxylflavone-quinoline-amino molecular system with both intramolecular charge transfer (ICT) and excited-state intramolecular proton transfer (ESIPT) process, enabling FQ-OH with strong fluorescence in a wide range of 550–800 nm, covering red-to-near-infrared emission region and large stokes shift as much as 162 nm. Due to the promising spectra property, FQ-OH was then fabricated into a red-to-near-infrared fluorescent probe FQ-DNP for the selective detection of thiophenol via aromatic nucleophilic substitution (S N Ar) reaction mechanism. Spectra assays in the solution demonstrated that FQ-DNP displayed prominent turn-on fluorescence response to thiophenol in 550–800 nm with emission peak at 627 nm, excellent selectivity, and exceptional sensitivity (detection limit as low as 7.2 nM). In addition, thiophenol in vapor form could be detected by FQ-DNP coated test papers enabling naked eye detection. Moreover, FQ-DNP was utilized for detecting thiophenol in environmental samples and showed great recovery results. Furthermore, biological application of FQ-DNP in living cells through cell imaging study demonstrated apparent intracellular fluorescence enhancement before/after thiophenol addition. [Display omitted] • A red-to-near-infrared fluorescent probe FQ-DNP for the selective detection of thiophenol was obtained. • FQ-DNP displayed excellent selectivity and exceptional sensitivity (detection limit as low as 7.2 nM). • Thiophenol in vapor form could be detected by FQ-DNP coated test papers enabling naked eye detection. • Detection of thiophenol in environmental samples by FQ-DNP showed great recovery results. • FQ-DNP demonstrated apparent intracellular fluorescence enhancement before/after thiophenol addition. [ABSTRACT FROM AUTHOR]

Based on the 7-nitro-1,2,3-benzoxadiazole (NBD) unit, many fluorescent probes have been developed for the differential detection of biothiols. Among them, however, the use of fluorescent probes for rapid simultaneous identification of biothiols in vivo has been rarely reported. In this work, a simple fluorescent probe (NC-NBD) is rationally designed and developed according to the different reactivity of biothiols, which can simultaneously distinguish homocysteine (Hcy), cysteine (Cys), and glutathione (GSH) by adjusting two different fluorescence signals (green and yellow). The probe NC-NBD can discriminatively detect biothiols using two fluorescence channels with fast response (120–360 s), which is suitable for real-time monitoring of biothiols in biological systems. As expected, the probe NC-NBD with excellent performance is able to determine the levels of Cys/Hcy and GSH in human serum samples, and therefore has potential applications in biological specimens. The robust probe shows low toxicity and high sensitivity when applied to living cells, and successfully achieves rapid sequence distinguishing of biothiols and intracellular imaging by using two different fluorescence signals. The probe can provide an effective tool for the real-time monitoring of intracellular biothiols. Image 1 • A fluorescent (FL) probe based on 7-nitro-1,2,3-benzoxadiazole (NBD) was developed. • The simple probe was used for rapid and sensitive sequence detection of biothiols in vitro. • The probe can determine the levels of Cys/Hcy and GSH in human serum samples. • The probe senses biothiols by two FL signals and images them in living cells. [ABSTRACT FROM AUTHOR]

In this report, a mitochondria-targeted probe based on an efficient platform constructed by pyridinium-coumarin and 2-dicyanomethylene-3-cyano-4,5,5-trimethyl-2,5-dihydrofuran (TCF) with high selectivity and sensitivity toward SO 2 derivatives was presented. As far as we know, pyridinium-coumarin is first used as a donor moiety to construct a FRET system. Compared with our previous work, it showed better solubility, higher biocompatibility and faster response speed. It also presented low detection limit (80.5 nM), excellent energy transfer efficiency (98.2%) and low cytotoxicity. Moreover, the probe could detect exogenous and endogenous bisulfite in living cells as well as in mitochondria successfully. Image 1 • A new FRET-based ratiometric fluorescence probe (named PCPT) for HSO 3 −/SO 3 2− was developed. • Probe PCPT showed a large pseudo Stokes shift (213 nm), high selectivity, sensitivity. • Probe PCPT could target well mitochondria in cell image. • Probe PCPT could image endogenous HSO 3 −/SO 3 2− in HepG2 cells. [ABSTRACT FROM AUTHOR]

A simple high selective and sensitive fluorescent pH probe based on a new seven-membered BOPYIN (BO rondifluoride-3,3-dimethyl-2-[2-(2- PY rrolyl) ethenyl] IN dole, Probe-NH 2 , Scheme 1) has been designed and synthesized. With the increase of acidity (pH from 5.51 to 2.47), the emission intensity dramatically enhanced to strong fluorescence. The linear response range is from 5.5 to 3.0 with p K a = 3.63, which is suitable for pH detection in biological system. Moreover, this probe has excellent selectivity response to H+, short response time (less than 10 s), reversibility and low cytotoxicity. Possible sensing mechanism studies demonstrated that the linear response of the probes to acidity of solution is the conjugation of H+ with response site N atom in primary amino group on BOPYIN. Besides, the fluorescent change of the Probe-NH 2 relies on PET and/or ICT process which is proved by experiment and further confirmed by DFT theoretical calculation. Finally, the probe has been successfully applied for visual detection and cellular imaging. Image 1 • A novel BOPYIN based 'turn-on' fluorescent probe for acidic pH was developed. • The PET/ICT mechanism is confirmed by spectra and DFT calculations studies. • There is no significant interference caused by common metal ions to this pH probe. • This probe can be used in real-time and reversible pH sensing. • Applications were carried out for visual detection and cellular imaging. [ABSTRACT FROM AUTHOR]

A novel click-derived monostyryl BODIPY-based fluorescent probe has been prepared. Notably, upon exposure to Hg2+ or Cu2+, it exhibited remarkable blue-shifted absorptions from 592 to either 555 for Hg2+ or 502 nm for Cu2+ with distinct color changes from blue to purple for Hg2+ or yellow for Cu2+ in CH 3 CN/H 2 O. Interestingly, its fluorescence showed significant ratiometric (Hg2+) and ON-OFF (Cu2+) changes. Notably, the probe displayed ratiometric fluorescence from 690 to 602 nm with a 65-fold enhancement in fluorescence ratio of I 602 /I 690 for Hg2+ and underwent a substantial ON-OFF fluorescence for Cu2+. Furthermore, this probe was successfully used in Hela cells and could easily discriminate Hg2+ and Cu2+ through double-channel imaging. These overall results illustrate that this monostyryl BODIPY potentially serves as a remarkable colorimetric probe for fluorescent ratiometric and ON-OFF discriminative detection of Hg2+ and Cu2+ in solutions and living cells by a remarkable double-channel change. Image 1 • A novel monostyryl BODIPY-based probe was prepared through click reaction. • Colorimetric changes from blue to purple for Hg2+ or yellow for Cu2+ were easily seen. • It showed large ratiometric for Hg2+ and ON-OFF for Cu2+ fluorescence. • It successfully distinguished Hg2+ and Cu2+ in living cells by double-channel imaging. • A 37-fold enhanced ratio for Hg2+ and a sufficient quenching for Cu2+ were seen in cells. [ABSTRACT FROM AUTHOR]

As an important sulfur-containing amino acid, aberrant levels of cysteine are closely related with an array of dieases. Although many Cys-specific fluorescent probes have been designed, most of them wouldn't be able to detect Cys in buffer solution, which limits the application of the probe in biological system. In this work, a novel near-infrared fluorescent probe Cys-WR with a large Stokes shift (about 110 nm) was developed for the detection of Cys by conjugating the fluorophore WR-4 with crotonate moiety. The probe exhibited off-on response to Cys with wide linear range of 0–100 μM, as well as the color of the probe solution changes from deep pink to brown observed by naked eyes. Moreover, the probe showed little cytotoxicity. Imaging of Cys using this probe in living A549 cells and zebrafish had also been well demonstrated. Image 1 • A novel near-infrared fluorescent probe Cys-WR with a large Stokes shift was constructed for detection of Cys. • The probe Cys-WR showed NIR off-on response to Cys with high sensitivity and selectivity. • The probe Cys-WR can be employed to monitor exogenous and endogenous Cys fluctuation in living cells and zebrafish. [ABSTRACT FROM AUTHOR]

A new fluorescence probe based on phenothiazine-coumarin platform was rationally designed and developed for the detection of hypochlorite in a ratiometric manner in aqueous solution and living cells. The probe possessed a large pseudo Stokes shift (209 nm) and lager gap between two emissions (462/629 nm), which should avail to perform more accurate detection. The probe could respond to hypochlorite with selectivity, sensitivity and celerity. Moreover, the probe was successfully used for imaging endogenous hypochlorite in mitochondria of RAW264.7 macrophage cells with high sensitivity. Image 1 • A novel ratiometric fluorescent probe (named PPC) for hypochlorite based on FRET platform was developed. • PPC showed a large pseudo Stokes shift (209 nm), high selectivity, sensitivity and fast response. • PPC could target well mitochondria in cell image. • PPC could image endogenous hypochlorite in RAW264.7 cells. [ABSTRACT FROM AUTHOR]

A new N-heterocyclic fluoran based dye BiF is facilely prepared in high yield by reaction of 5-methoxybenzimidazole and 2-(4-diethylamino-2-hydroxy)benzoylbenzoic acid in concentrated H 2 SO 4 , which keeps stable optical signals in water at pH values ranging from 4 to 10 and exhibits good living cell membrane permeability. By modification of the spirolactone in molecule BiF , a fluorescent probe BiF–Cu with specific and sensitive response to Cu2+ has been further developed, which contains a six-membered spirolic hydroxyethylhydrazide moiety that can be selectively triggered by Cu2+ among various metal ions through a specific cascade reaction of Cu2+-promoted spirolactam ring-opening and hydrolysis. A limit of detection for Cu2+ is calculated as 7.12 × 10−8 mol/L. In addition, the utilization of BiF–Cu for bioimaging Cu2+ in L929 cells demonstrates its living cell membrane permeability and makes it promising candidate for monitoring Cu2+ by cell imaging technology. A new N-heterocyclic fluoran BiF has been efficiently prepared by hybridizing benzimidazole and fluoran moieties. Based on this dye, fluorescent probe BiF–Cu with unique six-membered spirocyclic hydrazide has been developed for selective and sensitive detection of Cu2+ and cell imaging. Image 1 • A new N -heterocyclic fluoran dye was prepared with stable optical signal over a wide pH range. • A fluorescent probe containing a novel six-membered spirocyclic hydrazide trigger has been developed. • The probe was empolyed for highly selective and sensitive detection of Cu2+ with a detection limit of 71.2 nM. • The probe can be utilized in tracing Cu2+ in living cell. [ABSTRACT FROM AUTHOR]

A colorimetric and ratiometric fluorescent probe DTF for HSO 3 − was synthesized from natural and renewable nopinone. The fluorescent probe DTF can quantitatively detect HSO 3 − with high selectivity, sensitivity and fast response time (60 s). The detection process was accompanied with the visible color change from yellow to colorless and the fluorescent color change from green to blue. The fluorescence intensity ratio (F 430 /F 520) was linear with the concentration of HSO 3 − in the range of 0–80 μM, with a limit detection of 79.2 nM. The sensing mechanism was confirmed by 1H NMR and HRMS spectra. Above all, the novel fluorescent probe DTF was successfully applied to determine the concentration of HSO 3 − in food samples and HeLa cells. In this manuscript, we designed and synthesized a novel nopinone-based fluorescence probe for colorimetric and ratiometric detection of HSO 3 −, with high sensitivity, good selectivity and fast response time. The novel probe DTF was successfully applied for detection of the concentration of HSO 3 − in food samples and living HeLa cells. Image 1 • This is the first report that the synthesis of HSO 3 −-specific fluorescence probe based on nopinone. • The colorimetric and ratiometric fluorescent probe DTF can quantitatively detect HSO 3 − with high selectivity, sensitivity and fast response time. • Probe DTF was successfully applied for detection of the concentration of HSO 3 − in food samples and living HeLa cells. [ABSTRACT FROM AUTHOR]

Real-time monitoring of intracellular pH fluctuation is of great significance for diagnosis of diseases and study of related physiological and pathological processes. A novel near-infrared (NIR) pH-activated parent probe 4 was developed, and further functionalized to afford probes 6 and 7. With the decrease of pH from 11 to 2, they all exhibited a new absorption peak and strong fluorescence emission in NIR region, accompanied by rapid solution color change from pink to pale green. Moreover, the probes' fluorescence responses toward pH fluctuations were reversible and stable, and the pseudo-linear relationship between the fluorescence intensity and pH value can be used to detect pH value in 2.76–6.45 range quantitatively. Finally, probe 6 and 7 were successfully applied to monitor the fluctuation of intracellular pH by a fluorescence turn-on mode, and the imaging results confirmed their low cytotoxicity and satisfactory cell-membrane permeability, as well as their application prospect in disease diagnosis (such as tumor specific imaging) or assist in study of pH-related biological processes in wide acidic environment. Image 1 • Novel pH-sensitive NIR cyanine-based fluorescent probes (4 , 6 , 7) were developed. • All probes exhibited colorimetric and fluorescence responses to pH fluctuations. • The three probes could achieve quantitative detection of pH value in 2.76–6.45. • Probe 7 is a ratio fluorescent probe for pH. • Probe 6 and 7 were successfully applied to monitor intracellular pH fluctuations. [ABSTRACT FROM AUTHOR]

Minute fluctuation in the intracellular pH is usually related to common diseases. The construction of fluorescent probes with wide response range, high selectivity, excellent sensitivity and good reversibility for intracellular pH detection is of great significance. In this work, we developed a novel pH probe (ZJ) based on a 3-hydroxy naphthalimide derivative via the optimization of substitute groups. ZJ showed a satisfying fluorescence performance to pH changes. ZJ manifests a remarkable fluorescence enhancement at 468 nm (over 12-fold) from pH 2.5 to 10.0. Live cell imaging data uncovered that ZJ can be successfully used in monitoring intracellular pH changes led by chloroquine, inflammation and autophagy, and confirmed with flow cytometry analysis. All these features render ZJ a potential candidate to study pH-associated drug development and physiological and pathological processes. A novel off-on probe based on the 3-hydroxy naphthalimide is developed for imaging intracellular pH changes caused by chloroquine, inflammation and starvation, which would be helpful in the analysis of related drug development and disease. Image 1 • A new fluorescent off-on probe is developed for pH assay via the optimization of substitute groups. • The probe exhibits wide response range, high selectivity, excellent sensitivity and good reversibility for pH. • The probe is used to image intracellular pH changes led by chloroquine, inflammation and autophagy. [ABSTRACT FROM AUTHOR]