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.

Coumarin-Based Reversible Fluorescent Probe for Selective Detection of Cu2+ in Living Cells.

Copper ion plays an important role in many biological processes in human body. H2S is considered as the third gasses transmitter after carbon monoxide and nitric oxide. Here a novel ICT-based fluorescent ON-OFF-ON probe for Cu2+ and H2S detection was developed. Selectivity and sensitivity of probe was confirmed in aqueous Tris-HCl buffer (10 mM, pH 7.4, containing 90% acetonitrile). Probe DF-CU shows high selectivity over other analytes. The degree of fluorescence quenching is linearly associated with the concentration of Cu2+ (R2 = 0.9919). The limit of detection (LOD, calculated according to the 3σ/slope) for Cu2+ was 6.4 µM. Probe can work in almost all pH. The probe shows a very fast response to Cu2+ (within 10 s). Its response to copper ion could be reversed by H2S. The complex of probe with Cu2+ could be used for H2S detection. Furthermore, this ON-OFF-ON fluorescent probe successfully applied in the living cells for the detection of Cu2+ and H2S.

Recent development in dual function fluorescence probes for HOCl and interaction with different bioactive molecules.

Reactive oxygen species (ROS), reactive sulfur species (RSS), metal ions, and nitrogen species (RNS) play important roles in a variety of biological processes, such as a signal transduction, inflammation, and neurodegenerative damage. These species, while essential for certain functions, can also induce stress-related diseases. The interrelation between ROS, RSS, Metal ions and RNS underscores the importance of quantifying their concentrations in live cells, tissues, and organisms. The review emphasizes the use of small-molecule-based fluorescent/chemodosimeter probes to effectively measure and map the species' distribution with high temporal and spatial precision, paying particular attention to in vitro and in vivo environments. These probes are recognized as valuable tools contributing to breakthroughs in modern redox biology. The review specifically addresses the relationship of HOCl/ClO‾ (hypochlorous acid/Hypochlorite) with other reactive species. (Dual sensing probes).

A coumarin based Schiff Base: An effective colorimetric sensor for selective detection of F- ion in real samples and DFT studies.

Chemosensors are molecular devices which react with target and give a visible signal, which is a degree of its sensitivity. Herein, a novel coumarin based Schiff Base has been synthesized for F- ions detection. The chemosensor showed an intense color change upon the addition of F- ions (light yellow to purple). The chemosensor has fewer effects of competing anions. The limit of detection is calculated as low as 1.1 × 10-6 and the binding constant was determined as 1.61 × 104. The job's plot confirmed 1:1 stoichiometry between chemosensor and F- ion. The reverse reaction of chemosensor with MeOH is useful to construct a combinatorial logic circuit gates. The interaction mechanism of chemosensor was deliberated by 1H NMR, FTIR, and DFT studies. Finally, the chemosensor was useful to detect F- ions in tooth-paste sample and test strip is prepared for F- ions detection.

Irreversible coumarin based fluorescent probe for selective detection of Cu2+ in living cells.

Copper ion (Cu2+) is an essential part of the living organisms. Cu2+ ions play a vital role in many biotic processes. An abnormal amount of Cu2+ ions may result in serious diseases. Herein, a novel "fluorescent ON" probe NC-Cu to trace minute levels of Cu2+ ions in presence of various biological active species has been developed. Lysosomal cells targeting group (Morpholine) was added to the probe. The spectral properties of probe NC-Cu were recorded in HEPES buffer (0.01 M, pH = 7.4, comprising 50% CH3CN, λex = 430 nm, slit: 5 nm). The synthesized probe NC-Cu work based on copper promoted catalytic hydrolysis of hydrazone and shows remarkable fluorescence enhancement. The reaction of the probe with Cu2+ ions was completed within 20 min. An excellent linear relationship (R2 = 0.9952) was found and the limit of detection (LOD, according to the 3σ/slope) for Cu2+ ions was calculated to be 5.8 µM. Furthermore, NC-Cu was effectively functional in the living cells (KYSE30 cells) to trace Cu2+ ions.

A DCM-based NIR sensor for selective and sensitive detection of Zn2+ in living cells.

Zinc ion is the 2nd abundant transition metal element in human's body. It is responsible for many physiological and biological functioning in the body, such as growth of people, immunity, endocrine, etc. The deficiency of zinc could result in an increasing risk for growth retardation, neurological disorder and infectious disease. Thus, developing a nondestructive method for detecting Zn2+ in living systems is important. Here we reported a 2-(2-methyl-4H-ylidene)- malononitrile (DCM)-based NIR probe DF-Zn for selective and sensitive detection of Zn2+. The probe DF-Zn is cell-permeable and stable at broad pH range. DF-Zn showed a fast response to Zn2+, big stock's shift, and "nude-eye" recognition for Zn2+. Moreover, the selective binding of probe DF-Zn to Zn2+ was reversible. With the addition of EDTA in buffer solution, reversible response of probe to Zn2+ could be observed in MCF-7 cells imaging.