A novel coumarin-based fluorescence enhancement and colorimetric probe for Cu2+ via selective hydrolysis reaction

Development in Fluorescent OFF-ON Probes Based on Cu2+ Promoted Hydrolysis Reaction of the Picolinate Moiety

Anions and cations have a key role in our normal life. Cu²⁺ ion is a crucial trace element accountable for the part of several cellular enzymes and proteins, including cytochrome c oxidase, dopamine monooxygenase, Cu/Zn superoxide dismutase, and ceruloplasmin. WHO has found the extreme acceptable level of Cu²⁺ ions in drinking water is up to 2.0 ppm. Excess use of Cu²⁺ ions is associated with various human genetic disorders. Thus, the visualization of Cu²⁺ ions to avoid its toxic effects in chemical and biological systems is significant. In this review we have summarized sensors based on catalytic hydrolysis of picolinate to detect Cu²⁺ ions. The sensors based on hydrolysis of picolinate are very selective as compared to the other sensors for Cu²⁺ ions detection. We have focused on describing the structure, spectral properties, detection limits, and bioimaging model of the sensors.

Hetarenocoumarins based on 7-hydroxy-3-(benzothiazol-2-yl)coumarin

The syntheses of angular hetarenocoumarins, namely chromeno[8,7-e][1,3]oxazin-2-ones and furo[2,3-h]chromen-2-one, have been accomplished starting from 7-hydroxy-3-(benzothiazol-2-yl)-coumarin using aminomethylation and formylation reactions.

A turn-on red-emitting fluorescent probe for determination of copper(II) ions in food samples and living zebrafish

Herein, we developed a turn-on red-emitting fluorescent probe for the sensitive and selective detection of copper ions (Cu²⁺) in food samples and living zebrafish. The probe employs a hemicyanine scaffold as the fluorophore and a 2-pyridinecarbonyl group as the recognition receptor and quenching moiety. The 2-pyridinecarbonyl moiety can be specifically cleaved by Cu²⁺ and results in an approximately 18-fold fluorescence enhancement of the probe, thereby providing a fluorescence turn-on assay for Cu²⁺. Additionally, the probe exhibited excellent selectivity, high sensitivity, a broad linear relationship (0.020 to 8.0 μM), and a low limit of detection (4.0 nM, S/N = 3) for Cu²⁺. Concomitantly, the probe exhibited satisfactory analytical performance when used with actual food samples. Moreover, the probe could be used for in situ determination of Cu²⁺ in both living plant tissues and in living zebrafish.

A novel colorimetric and "turn-off" fluorescent probe based on catalyzed hydrolysis reaction for detection of Cu2+ in real water and in living cells

A novel and highly selective fluorescent 1,8-naphthalimide-based probe, 3, was designed and synthesized for rapid Cu²⁺ detection in a CH₃CN-H₂O (3:1, v/v, pH = 7.4) solution by means of a distinct hydrolysis mechanism via its Cu²⁺-promoting feature. Upon treatment with Cu²⁺, the fluorescence response of probe 3 at 550 nm abruptly decreased, which was visible to the naked eye, and this response was accompanied by a clear change of the color of the solution; the color changed from the original yellow color to colorless. This color change occurred due to the Cu²⁺-promoted hydrolysis of 3, which yielded a fluorescence-quenched product. It is inspiring that probe 3 exhibited excellent sensitivity, a short response time and strong anti-interference recognition. Compared with the allowable amount of Cu²⁺ (∼20 μM) in drinking water, the detection limit of 3 for Cu²⁺ is calculated to be 9.15 nM, which is much lower than the amount defined by standards. The probe can be successfully applied for the determination of Cu²⁺ in real aqueous samples. Furthermore, probe 3 can be used as a fluorescent sensor to detect Cu²⁺ in biological environments, demonstrating its low toxicity to organisms and good cell permeability in live cell imaging.

A new hydrazone-based colorimetric chemosensor for naked-eye detection of copper ion in aqueous medium

A new hydrazone-based colorimetric Cu2+ chemosensor is synthesized. Its structure was confirmed by single-crystal X-ray diffraction. Its binding properties towards various metal ions are examined through absorption spectroscopy. In aqueous THF solution, the chemosensor exhibits selective recognition towards Cu2+ over other metal ions with a colour change from colourless to pink. The complex formed between the chemosensor and Cu2+ ions forms a 2:1 stoichiometry with an association constant of 2.46 × 108M−2. The analytical detection limit for Cu2+ by the naked eye is as low as 10.0 μM.

Coumarin-Based Small-Molecule Fluorescent Chemosensors

Coumarins are a very large family of compounds containing the unique 2H-chromen-2-one motif, as it is known according to IUPAC nomenclature. Coumarin derivatives are widely found in nature, especially in plants and are constituents of several essential oils. Up to now, thousands of coumarin derivatives have been isolated from nature or produced by chemists. More recently, the coumarin platform has been widely adopted in the design of small-molecule fluorescent chemosensors because of its excellent biocompatibility, strong and stable fluorescence emission, and good structural flexibility. This scaffold has found wide applications in the development of fluorescent chemosensors in the fields of molecular recognition, molecular imaging, bioorganic chemistry, analytical chemistry, materials chemistry, as well as in the biology and medical science communities. This review focuses on the important progress of coumarin-based small-molecule fluorescent chemosensors during the period of 2012-2018. This comprehensive and critical review may facilitate the development of more powerful fluorescent chemosensors for broad and exciting applications in the future.

A highly sensitive and selective fluorescent probe for determination of Cu (II) and application in live cell imaging

A highly sensitive fluorescent probe, 2‑butyl‑6‑(2‑ethylidenehydrazinyl)‑1H‑benzo[de]isoquinoline‑1,3(2H)‑dione (P) has been designed and synthesized to detect Cu²⁺ in CH₃CN-HEPES (4:1, v/v, pH = 7.4) solution. This probe functions via a distinctive hydrolysis mechanism through Cu²⁺-promoted accompany by extinction of the fluorescent and other competing metal ions did not showed any interference. The limit of detection toward Cu²⁺ was calculated of 320 nM. Probe P was not only successfully used for the determination of trace level Cu²⁺ in the CH₃CN-HEPES (4:1, v/v, pH = 7.4) solution, but also valid for fluorescence imaging of Cu²⁺ in lysosomes of 293T cells and it was applied in real water samples. This work indicated that P would be of great application prospect in environmental monitoring and medical diagnosis.

A new pyrazoline-based probe of quenched fluorescent reversible recognition for Cu2+ and its application in cells

A new pyrazoline-based probe D was designed and synthesized, which can be used as a highly sensitive, selective and reversible recognizing fluorescent to detect Cu²⁺. The recognition properties of this compound was investigated by UV-vis absorption and fluorescence spectrophotometry. The results showed that the probe D forms a 1:1 complex with Cu²⁺ and displayed a linear fluorescence response to Cu²⁺ with a detection limit of 1.94×10^-7M. In addition, the probe have a good biocompatibility in living cells.