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• The synthetic route of the probe is very simple. • The probe has good reversibility in physiological environment. • The probe Cu-1 shows excellent selectivity toward Cys. • This assay has high sensitivity and exhibits short response time. • This probe is AIE-active leading to high luminous efficiency in cell imaging. In this work, an effective and simple aggregation-induced emission (AIE) active fluorescent probe based on ESIPT luminescence principle, 2-hydroxy-1-naphthal-4-aminoantipyrine (1), was synthesized via a simple chemical reaction. It displayed strong fluorescence enhancement in water. The AIE mechanism of 1 was explored by electron microscopy and computational analysis. We demonstrate the combination effect of intramolecular hydrogen bonds and π-π stacking to endow 1 with such a property. Importantly, the ensemble of 1 with copper ions (Cu-1) as a fluorescent probe enables highly selective and sensitive turn-on fluorescence detection of cysteine (Cys) over other interfering substances. Under optimal detection conditions, this probe has a good linear relationship in the concentration range of Cys between 0 and 8 μM, and the detection limit of Cys was estimated as 84 nM. Furthermore, this assay exhibits good reversibility of 1 to Cu2+ and Cys. Due to its good biocompatibility evaluated by CCK-assay, the probe Cu-1 was finally applied in imaging of Cys within Min6 cells successfully. [ABSTRACT FROM AUTHOR]

A novel dual site controlled probe has been developed on the basis of rhodamine and biphenylcarbonitrile unit. The probe showed not only rapid fluorescence response to pH, but also good colorimetric recognition performance for copper ions in the HEPES buffer solution (pH 7.0). The optimal geometric configuration of the probe RhB-H with different structures and the [RhB-H-Cu 2+ ] complex were calculated at B3LYP level by DFT method. On this basis, the response mechanism of pH was analysed combining with the 1 H NMR titration experiment. Moreover, the cytotoxicity studies indicated that the probe had good biocompatibility and low toxicity. Then the probe was also successfully applied on real-time monitoring of the intracellular pH changes by exhibiting different fluorescence and emission intensity. These results demonstrated that the probe could be usefully involved in biological and biomedical research. [ABSTRACT FROM AUTHOR]

A rhodamine-based fluorescent chemdosimeter SHR for Cu 2+ has been developed based on the spirocyclic ring-opening mechanism. SHR is colorless and nonfluorescent due to intramolecular spirocyclization. Upon incubation with Cu 2+ in aqueous media, a highly efficient ring opening of SHR occurs via Cu 2+ -promoted phenylhydrazine oxidation, causing a dual chromogenic and fluorogenic response. The fluorescent intensity at 580 nm increases linearly with Cu 2+ concentration and as low as 10 nM of Cu 2+ can be readily detected. The proposed chemodosimeter shows high selectivity toward Cu 2+ over other metal ions and proves to be able to image Cu 2+ levels in live cells. [ABSTRACT FROM AUTHOR]

Quinoline based novel fluorescent probes have been synthesized for the selective and sensitive detection of Cu 2+ ions. The probes FQ-1 and FQ-2 exhibit a turn-on fluorescence response towards Cu 2+ ions under physiological conditions in living cells as well. The detection limit of Cu 2+ using the probes FQ-1 and FQ-2 was found to be 1.8 nM and 44.2 nM respectively. [ABSTRACT FROM AUTHOR]

An efficient fluorescein based probe (H 2 L) for the dual sensing of Al 3+ and Cu 2 + has been synthesized and characterized. H 2 L was highly selective toward these two ions with different fluorescence signals and binding modes in two different media. In EtOH-H 2 O (3:2, v/v; pH 4.0), H 2 L selectively binds Al 3+ to form a 1:1 ligand/metal complex, giving rise to a visible pale pink-to-yellow color change and fluorescence enhancement at 440 nm, while in CH 3 CN-H 2 O (2:3, v/v; pH 7.2), H 2 L and Cu 2+ form a 1:2 ratio complex, resulting in a color change from pink to orange-yellow and a significant fluorescence enhancement at 520 nm. The binding modes were confirmed by fluorescence, absorption, IR, ESI-MS and 1 H NMR titrations. The detection limits were calculated to be 7.32 × 10 −8 M and 1.47 × 10 −8 M for Al 3+ and Cu 2+ , respectively. Cell imaging studies demonstrate that this sensor is capable of sensing Al 3+ and Cu 2+ in living cells. [ABSTRACT FROM AUTHOR]

A new and dual-response fluorescent probe (QLBM) based on quinoline and benzimidazole groups has been designed and developed for recognition of copper(II) ion (Cu 2+ ) and iron(III) ion (Fe 3+ ) simultaneously. This sensor displays a favorable selectivity for Cu 2+ and Fe 3+ ions over a range of other common metal cations in 100% aqueous medium (50 mM Tris buffer, pH 7.2), leading to prominent fluorescence on-off. The detection limits were 1.35 × 10 −7 M for Cu 2+ and 1.24 × 10 −7 M for Fe 3+ respectively. This dual-response fluorescent probe for Cu 2+ and Fe 3+ was distinguished by further reduction of the ascorbic acid. It is reported for the first time to use ascorbic acid to discriminate Cu 2+ and Fe 3+ by fluorescent probe technology. The recognizing mechanism of QLBM toward Cu 2+ and Fe 3+ has been investigated in detail by NMR, HR-MS and density functional theory (DFT) calculations. Moreover, further application of the sensor in fluorescence imaging was studied in HeLa cells due to the low cytotoxicity and good photophysical properties, suggesting that QLBM could be used as a fluorescent sensor for tracking Cu 2+ and Fe 3+ in cells. [ABSTRACT FROM AUTHOR]

Based on fluorescent resonance energy transfer (FRET), we developed a ratiometric fluorescent probe 1 for sensing Cu 2+ . As expected, probe 1 exhibited high selectivity and excellent sensitivity in both absorbance and fluorescence detection of Cu 2+ in aqueous solution. A significant color change from pale yellow to pink could be observed, enabling naked-eye detection of Cu 2+ . Furthermore, fluorescence imaging experiment of Cu 2+ in living MGC-803 cells demonstrated its value of practical applications in biological systems. [ABSTRACT FROM AUTHOR]

The present article deals with the detailed complexation study along with exploration of possible utilization of 25,26,27,28- tetra -hydroxy-11,23- di -( tert -butyl)-5,17- di -(2-antracenyl)azocalix[4]arene (7 ) and 25,26,27,28- tetra -hydroxy-11,23- di -( tert -butyl)-5,17- di -(1-pyreneyl)azocalix[4]arene (8) as bio-imaging fluorescent probe to detect Cu 2+ in human colon cell line, SW-620, observed by fluorescence microscopy. Complexation properties of ligands 7 and 8 toward selected transition metal ions have been investigated by UV–vis and fluorescence spectroscopies. It has been noticed that ligands 7 and 8 are not only proved to be an efficient Cu 2+ selective chromoionophore but also possess effective fluorescence properties by complexing with Cu 2+ ions. The FTIR spectroscopic method has also been applied for further confirmation of the complexation phenomenon of ligands 7 and 8 with metal ion and were found to be adequate. Moreover, fluorescence microscopy studies showed that ligand 7 may be used as fluorescent probe to detect Cu 2+ in living cells. [ABSTRACT FROM AUTHOR]

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

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

Abstract: Three new rhodamine Schiff base sensors 1a–1c have been designed and synthesized as highly sensitive and selective “off-on” chemosensors for Cu2+ detection via the rhodamine ring-opening approach. The sensors display remarkably Cu2+-selective orange fluorescence and pink color switch over a wide range of tested metal ions. Fluorescent imaging of Cu2+ in living cells is also successfully demonstrated. [Copyright &y& Elsevier]