Fluorescent probe for Cu2+ and the secondary application of the resultant complex to detect cysteine

Semi-quantitative and visual detection of Cu2+ and glyphosate in real samples and living cells using fluorescent and colorimetric dual-signals peptide-based probe

The excessive emission of copper ions (Cu2+) and the abuse of glyphosate (Glyp) have caused serious harm to the ecological environment and human health, so it is important to develop a fast and convenient method for the analysis of Cu2+ and glyphosate to ensure environmental and food safety. Herein, a dual-signals peptide-based probe (FASRH) with fluorescent and colorimetric was prepared using 5-carboxyl fluorescein modified tetrapeptide (Ala-Ser-Arg-His-NH2). FASRH was successfully used to recognize Cu2+ as a fluorescence "on-off" probe, forming the FASRH-Cu2+ complex with non-fluorescence. As a new promising cascade probe, FASRH-Cu2+ complex probe has high selectivity (only Glyp), good sensitivity (50.2 nM), good anti-interference ability and wide pH range (7.0-11.0) for the detection of glyphosate by ligand replacement method. In addition, the recognizable color changed markedly under 365 nm UV light and natural light. Notably, FASRH not only achieved accurate monitoring of Cu2+ and glyphosate in two real water samples, but also successfully applied to detect Cu2+ and glyphosate in live Hacat cells based on low cytotoxicity. Moreover, it is worth noting that FASRH-impregnated test strips exhibited significant fluorescence and colorimetric color changes for Cu2+ and glyphosate via naked eye. Furthermore, smartphone-assisted FASRH was used for the portable detection of Cu2+ and glyphosate based on the advantages of simplicity, low cost and fast response.

Strategies for Improving Selectivity and Sensitivity of Schiff Base Fluorescent Chemosensors for Toxic and Heavy Metals

Toxic cations, including heavy metals, pose significant environmental and health risks, necessitating the development of reliable detection methods. This review investigates the techniques and approaches used to strengthen the sensitivity and selectivity of Schiff base fluorescent chemosensors designed specifically to detect toxic and heavy metal cations. The paper explores a range of strategies, including functional group variations, structural modifications, and the integration of nanomaterials or auxiliary receptors, to amplify the efficiency of these chemosensors. By improving selectivity towards targeted cations and achieving heightened sensitivity and detection limits, consequently, these strategies contribute to the advancement of accurate and efficient detection methods while increasing the range of end-use applications. The findings discussed in this review offer valuable insights into the potential of leveraging Schiff base fluorescent chemosensors for the accurate and reliable detection and monitoring of heavy metal cations in various fields, including environmental monitoring, biomedical research, and industrial safety.

Three-fold interpenetrated metal–organic framework as a multifunctional fluorescent probe for detecting 2,4,6-trinitrophenol, levofloxacin, and l-cystine

A robust Zn(ii) MOF with good chemical and thermal stability, was prepared as an effective fluorescent probe for 2,4,6-trinitrophenol (TNP), levofloxacin (LVX) and l-cystine (l-Cys) with recyclability.

Development of a method for the detection of Cu2+ in the environment and live cells using a synthesized spider web-like fluorescent probe

A macrocyclic Schiff base fluorescent probe [1,2-phenylenediamine-2,6-pyridinedialdehyde macrocyclic Schiff base] (BP-MSB) based on 2,6-pyridinedialdehyde was synthesized for use in the detection of Cu²⁺ in environmental water samples and live cells imaging by the method of specific recognition. The free fluorescent probe BP-MSB shows strong fluorescence in DMSO/H₂O. The probe shows high sensitivity and selectivity for Cu²⁺ through "turn-off" fluorescence response in DMSO/H₂O buffer solution (pH = 6.5), with a detection limit of 0.83 nM, which is far below the maximum allowable drinking water content of 20.0 μM specified by the US Environmental Protection Agency. The BP-MSB fluorescence quenching method was used for the determination of Cu²⁺ in Xiang Jiang water samples and tap-water. Furthermore, addition of the same number of moles of ethylene diamine tetraacetic acid (EDTA) can realize the reversible recognition of Cu²⁺ by the probe BP-MSB. Most importantly, the fluorescence imaging of live cells after incubation of BP-MSB with GM12878 cells showed good imaging performance, confirming the sensitivity of the fluorescent probe BP-MSB in vivo. The probe was also used to form an analog logic gate. This probe has the advantages of good stability, simple operation and high selectivity, which provides a broad prospect for environmental monitoring, intracellular detection and practical application of POCT.

A Heterocyclic-based Bifunctional Sensor for Detecting Cobalt and Zinc Ion

A new bifunctional chemosensor HBP ((E)-2-(2-((5-bromopyridin-2-yl)methylene)hydrazinyl) quinoline) based on heterocyclic compounds was designed and studied. The HBP showed successful detecting ability toward cobalt ion with a UV-visible red-shift and a color change of colorless to pink. Moreover, toward zinc ion, the HBP showed an obvious fluorescence turn-on response. The binding ratio of the HBP to cobalt and zinc was a 2 to 1 for both ions. The detection limits were found to be 10 nM for Co2+ and 18 nM for Zn2+. Based on UV-vis and fluorescent spectral variations, Job plots, ESI-MS, FT-IR and calculations, the binding mechanisms of the HBP toward cobalt and zinc ions were proposed.

A coumarin derivative-Cu2+ complex-based fluorescent chemosensor for detection of biothiols

Herein, a novel fluorescent sensor has been developed for the detection of biothiols based on theoretical calculations of the stability constant of the complex between a Cu2+ ion and (E)-3-((2-(benzo[d]thiazol-2-yl)hydrazono)methyl)-7-(diethylamino) coumarin (BDC) as a fluorescent ligand. In this study, on the basis of density functional theory method, the Gibbs free energy of ligand-exchange reaction and the solvation model were carried out using thermodynamic cycles. The obtained results are in good agreement with the experimental data. The BDC-Cu2+ complex can be used as a fluorescent sensor for the detection of biothiols in the presence of non-thiol containing amino acids, with a detection limit for cysteine at 0.3 μM. Moreover, theoretical calculations of excited states were used to elucidate variations in the fluorescence properties. The computed results show that the excited doublet states D2 and D1 are dark doublet states, which quench the fluorescence of the complex.

A Review on Schiff Base Fluorescent Chemosensors for Cell Imaging Applications

Fluorescent determinations of analytes have proven to be a powerful method due to their simplicity, low cost, detection limit, rapid photoluminescence response, and applicability to bioimaging. Fluorescence imaging as a powerful tool for monitoring biomolecules within the living systems. Schiff base has been extensively used as strongly absorbing and colorful chromophores in the design of chemosensors. In recent years, Schiff base based fluorescent probes have been developed for the detection of various toxic analytes and imaging of various analytes in biological systems. This review gives an overview of the important fluorescent sensors which are based on Schiff base, their approaches for molecular recognition, and their potential application in bioimaging studies.

Acetonitrilated Unsymmetric BODIPYs having glycine fluorescence responsive quenching: Design, synthesis and spectroscopic properties

A series of novel N≡C-CH₂-B-F system BODIPY were designed and synthesized by introducing aldehyde and acetonitrile units which gave positive influence to spectroscopic and chemical properties of BODIPY derivatives. The effects of glycine (Gly) on the target products were studied via ultraviolet and visible spectrophotometry (UV-Vis) and photoluminescence (PL) under different conditions of the presence and absence of cations (K⁺, Ca²⁺, Zn²⁺). It was showed that glycine has an intense quenching effect on the compounds in both the presence and absence of ions with a dramatic color change from notable red to light orange owing to the addition of Gly. With regard to cells imaging investigation, the products showed the prominent fluorescence in cholangiocarcinoma cells. The luminescent effect of compounds 1 and 3 entering the cells was significantly stronger than that of compound 2. In addition, pertaining to anticancer properties, two human cancer cell lines (RBE, HCCC-9810) and one normal cell line (L-02) were evaluated for in vitro cytotoxicity. The target compounds, 1-3, exhibited moderate antitumor activity, of which compound 1 was found to be the most potent derivative with IC₅₀ values of 119.31 ± 6.25, 114.73 ± 3.25, and 106.33 ± 5.22 against RBE, HCCC-9810, and L-02 cells, respectively, slightly weaker than the positive control 5-FU.