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A new hemicyanine-based near-infrared "off-on" recognition Cu2+ fluorescent probe NRh-NP was designed and successfully synthesized. The structure of NRh-NP was characterized by NMR, ESI-HRMS and single crystal X-ray diffraction analysis. NRh-NP has high sensitivity, selectivity and a low limit of detection (33 nM as fluorescence sensor and 35 nM as UV sensor) to Cu2+. According to Job's plot and ESI-HRMS, the coordination ratio of NRh-NP to Cu2+ was 1:1. DFT theoretical calculations proved that the sensor mechanism was photo-induced electron transfer (PET). More importantly, NRh-NP has excellent membrane permeability and low cytotoxicity, which could be used not only for the detection of Cu2+ in human breast cancer cells (MCF-7), but also for imaging Cu2+ in living mice. [Display omitted] • The structure of NRh-NP was characterized by NMR, ESI-HRMS and single crystal X-ray diffraction analysis. • The responses of NRh-NP toward Cu2+ were fully proved by Job's plot, ESI-HRMS and DFT theoretical calculations. • NRh-NP has high sensitivity and selectivity with detection limit as low as 33 nM. • NRh-NP can be used for Cu2+ imaging in living cells and in vivo. [ABSTRACT FROM AUTHOR]

Hypochloric acid (HOCl) plays vital roles in cell signaling and homeostasis which involved in many related diseases. Therefore, the accurate detected level of OCl− for discussing the complex contributions of OCl− to human health is of great significance. In this study, a novel mitochondrion-targeting fluorescent probe DMI bearing a carbon-carbon double bond as an OCl−-responsive site has been developed. Probe DMI exhibited specific fluorescence response toward OCl− with fast response (within 4 s) and high sensitivity (detection limit is 0.05 μM), where the obvious color changes could be observed by the naked eye. More importantly, DMI could be applied in the bioimaging of OCl− in living A549 cells successfully benefited from its good sensing properties and low toxicity. Fluorescence co-localization test was further carried out and confirmed mitochondria-targetable ability of DMI which can be used for investigating physiological function of HOCl at organelle levels. Image 1 • Probe DMI is a mitochondria-targeting visual fluorescence probe. • DMI could highly sensitive and selective detected of hypochlorite. • The mechanism of DMI has been proved to be via oxidation fracture of C C. • DMI can be used to imaging of OCl− in living A549 cells. [ABSTRACT FROM AUTHOR]

• Dehydroabietate-based fluorescent probe for Hg2+ and Fe3+ was synthesized and characterized. • Detection limits of the sensor were 31.0 nM and 31.2 nM for Hg2+ and Fe3+ ions, respectively. • The sensor have a wide pH range for ion detection (5 ~ 12), and a short response time (10 s). • Fluorescent imaging experiments using MCF-7 and SMCC-7721 cell were carried out successfully. A novel dehydroabietic acid-based fluorescent probe (DBH) containing 2,4-diarylbenzimidazole moiety was designed and synthesized, and the compound was characterized by its UV–Vis, FT-IR, 1H NMR, 13C NMR and ESI-MS spectra. DBH could be used for the detection of Fe3+ and Hg2+ through the selective fluorescence quenching in EtOH/H 2 O solution. The probe DBH showed excellent selectivity and sensitivity towards Fe3+ and Hg2+ over other metal ions. The limits of detection were calculated as 3.12 × 10−8 M and 3.10 × 10−8 M, respectively. Especially, DBH have a wide pH range for ion detection (5 ~ 12), and a short response time (10 s). Job's plot method in combination with ESI-MS and FT-IR spectra was used to determine the stoichiometry of DBH -Fe3+/Hg2+ complexes as both 2:1. Moreover, DBH exhibited low cytotoxicity to MCF-7 and SMCC-7721 cells (IC 50 > 100 μM). In the fluorescent cell imaging experiments, DBH could be used as a prominent intracellular probe for the detection of Fe3+ and Hg2+ in living cells. [ABSTRACT FROM AUTHOR]

• A novel turn-on probe (ABTT-MA) based on "AIE + ESIPT" effect was developed. • The maleimide-appended probe presents high selectivity to Cys over structure-like Hcy and GSH. • New insight into the high selectivity of maleimide-appended probe: Michael addition/S,N-intramolecular rearrangement cascade reaction. • ABTT-MA was allowed in aqueous media with the lowest detection limit (9.4 nM). • ABTT-MA was successfully applied to imaging exogenous and endogenous Cys in living cells. Biothiols, including cysteine (Cys), homocysteine (Hcy) and glutathione (GSH), play pivotal roles in numerous physiological events, however, due to the similar structures and reactivities, differentiation of these biothiols remains a challenging task. Herein, we reported a maleimide-appended fluorescent probe ABTT-MA capable of specific sensing of Cys over other structure-alike biothiols with an ultralow detection limit (9.4 nM). Via a series of investigations into the mechanism, the high selectivity toward Cys is ascribed to a Michael addition/S,N-intramolecular rearrangement cascade reaction, in which the involvement of the mercapto and the adjacent amino groups is necessary to proceed the sensing process. Given this presupposition, Cys could be kinetically discriminated from Hcy and GSH. Upon the addition of Cys, a strong fluorescence appeared and the intensity at 503 nm was correlated with Cys concentration linearly over a wide range (0–10 μM). Thanks to the aggregation-induced emission (AIE) and excited-state intramolecular proton transfer (ESIPT) activity, the selective detection of Cys was realized not only in aqueous media but in the paper-based point-of-care test (POCT). Significantly, the practicability of ABTT-MA in exogenous and endogenous Cys imaging in living cells was elucidated as well. [ABSTRACT FROM AUTHOR]

As one of the reactive oxygen species (ROS), hypochlorous acid (HOCl) plays a key role in the pathogenesis of a range of diseases. The detection of HOCl has been a hot research topic. Herein, this paper proposes a new conjugate of 4-hydroxy-1,8-naphthalimide and p -methylaminophenylether as fluorescent probe HNPE with simple synthesis and excellent performances to detect HOCl. The probe has a good linear relationship with HOCl (0–1 μM), and its detection limit is 6.56 nM. Moreover, this probe has good selectivity, which can distinguish HOCl from other common analytes. Importantly, the probe HNPE has some achievements in HOCl imaging of living cells and zebrafish. Hence, the probe HNPE is competent as a tool to visualize HOCl in biosystems. Image 1 • Probe HNPE with the p -alkylaminophenylether moiety showed high sensitivity to HOCl (DL = 6.56 nM). • Probe HNPE exhibited preeminent selectivity towards HOCl over other reactive oxygen species. • Probe HNPE was applied to the visualization of native HOCl in living cells and zebrafish. • The concise p -alkylaminophenylether moiety could be used to construct different types of HOCl fluorescent probes. [ABSTRACT FROM AUTHOR]

A novel quinazolinone based turn-on fluorescence probe for sensitive monitoring hypochlorite was prepared using the mild condensation reaction between 2-(2′-hydroxyphenyl)-4(3H)-quinazolinone derivative and 4-methylbenzenesulfonyl hydrazide. The probe exhibited specific selectivity to ClO− with obvious optical signal changes from weak fluorescence at 560 nm to a strong fluorescence emission at 520 nm and color changes from colorless to yellow, which could be noticed by the naked eye. The detection limit toward hypochlorite is as low as 11.4 nM. Moreover, the probe could sensitively response to ClO− in living cells with satisfying imaging effect and has been successfully applied to the determination of ClO− in practical water samples, which indicated that the probe has certain application potential for hypochlorite monitoring. Unlabelled Image • A quinazolinone based fluorescent probe for detection of ClO− was designed and synthesized. • Probe QBH showed a rapid and remarkable fluorescence "turn-on" response to ClO−. • The QBH could detect ClO− quantitatively with a detection limit as low as 11.4 nM. • The sensing mechanism is analyzed through the NMR and MS spectra. • The probe was successfully applied to the determination of ClO− in practical water samples. [ABSTRACT FROM AUTHOR]

In this study, a mitochondria-specific fluorescent probe for efficient ratiometric detection of Cys was designed and investigated. Probe 1 is composed of a xanthylene skeleton and a benzyl group containing an acryloyl moiety. The probe showed excellent water solubility, good selectivity and sensitivity toward Cys over other analytes, and afforded an extremely low detection limit of 33.7 nM. The possible detection mechanism was ascertained by HRMS analysis. Moreover, probe 1 had excellent mitochondrial-targeting ability (the Pearson's correlation coefficient was 0.96), and was capable of monitoring endogenous Cys in living HeLa cells by dual channel ratiometric bioimaging, demonstrating its significant potential in biological applications. Image 1 • A novel ratiometric and mitochondria-targetability fluorescent probe 1 with a xanthylene skeleton for Cys was developed. • Probe 1 showed excellent water solubility, high selectivity and sensitivity (detection limit of 33.7 nM) towards Cys. • Probe 1 could be successfully used for imaging cellular exogenous and endogenous Cys. [ABSTRACT FROM AUTHOR]

• A novel bifunctional fluorescent probe CBTA was developed. • CBTA showed high sensitivity and selectivity to HSO 3 − and N 2 H 4 in ultrafast time. • CBTA has low detection limits for bisulfite and hydrazine. • CBTA could visualize endogenous HSO 3 − in living cells. The probe CBTA is a novel bifunctional fluorescent probe that can detect bisulfite and hydrazine hydrate in a rational manner. And probe CBTA could specifically detect bisulfite and hydrazine hydrate among different analytes. Moreover, the response time of probe CBTA to SO 2 derivatives and hydrazine is extremely short, and the detection limits for bisulfite and hydrazine are as low as 5.6 nmol and 39 nmol. Cellular experiments also indicated that the probe CBTA was low in cytotoxicity and could be applied to cellular fluorescence imaging. Therefore, the probe CBTA could provide an efficient means for detecting SO 2 derivatives and hydrazine in vitro. [ABSTRACT FROM AUTHOR]