A "Turn-On" fluorescent probe for detection and removal of Zn2+ in aqueous and its application in living cells

A turn-on AIE dual-channel fluorescent probe for sensing Cr3+/ClO- and application in cell imaging

A Cr3+/ClO--enhanced fluorescent probe, DNS (5-(dimethylamino)-N'-(2-hydroxy-4,6-dimethoxybenzylidene)-naphthalene-1-sulfonyl hydrazide), with aggregation-induced emission (AIE) properties was synthesized using dansylhydrazide and 4,6-dimethoxysalicylaldehyde as starting materials. The probe rapidly and selectively detects Cr3+ and ClO- in a solvent system of H2O/DMSO (2:8). Upon binding with Cr3+/ClO-, the probe exhibits a significant fluorescence enhancement, with minimal interference from other ions. The detection limits (LOD) were determined to be 5.36 × 10-7 mol/L for Cr3+ and 3.65 × 10-7 mol/L for ClO-. The binding mechanisms of DNS with Cr3+/ClO- were investigated through Job's plot, 1H NMR titration, and mass spectrometry. Furthermore, the probe's low cytotoxicity and biocompatibility suggest its potential for detecting exogenous Cr3+/ClO- and endogenous ClO- in living cells. DNS shows promise for real-time detection and bioimaging applications.

A novel fluorescent probe based on coumarin derivatives-grafted cellulose for specific detection of Fe3+ and its application

Fe3+ is one of the most important ions for maintaining the normal growth of plants and animals. However, imbalance and accumulation of Fe3+ can lead to serious damage to the environmental system. Hence, it is considerably crucial to monitor the concentration of Fe3+. In this paper, a high-performance fluorescent probe CA-NCC for specifically detecting Fe3+ was obtained by grafting cellulose acetate (CA) with coumarin derivative (NCC). The resulted probe displayed a bright blue fluorescence in THF solution and showed a distinct "turn-off" fluorescence response to Fe3+, while the small molecule compound NCC could not realize the detection of Fe3+. CA-NCC displayed excellent response performance to Fe3+ including excellent selectivity and sensitivity, rapid reaction time (2.5 min), wide pH detection range (6-11), and low detection limit (0.178 µM). More importantly, CA-NCC was successfully fabricated into fluorescent film based on the good processability of cellulose acetate, and achieved highly selective recognition of Fe3+ from various metal ions.

Interpret the potential role of zinc against oxidative stress in inflammation with a practical fluorescent assay

Zinc plays a critical role in inflammation and apoptosis, potentially offering new insights into health and disease beyond its established involvement in various biological processes. A fluorescent probe, SPI, has been designed and synthesized for the real-time detection of dynamic changes of zinc ions (Zn2+) in the potential resistance to oxidative stress, showing fluorescence enhancement at approximately 639 nm with a limit of detection of around 65 pM, which allowed it to identify even low concentrations of Zn2+ with intrinsic excellent biocompatibility. By establishing a cellular inflammation and apoptosis model using HT-DNA, hydrogen peroxide (H2O2), and dexamethasone (DXMS), the study effectively simulates conditions that can alter Zn2+ dynamics. Monitoring the fluorescence changes of SPI in response to these conditions allows researchers to observe how Zn2+ levels fluctuate in real-time, providing a clearer picture of its role in maintaining intracellular redox homeostasis. The findings indicate that SPI can be instrumental in elucidating the detailed molecular mechanisms through which Zn2+ influences immune responses and associates with cellular stress pathways. Overall, the development of SPI not only replenishes a potential assay into the toolbox to study Zn2+ in living cells but also opens new avenues for the further investigations into the therapeutic potential of modulating zinc levels in various pathological conditions.

A Portable Zn2+ Fluorescence Sensor for Information Storage and Bio-Imaging in Living Cells

A fluorescence probe (Probe-ITR) was designed and synthesized for the rapid detection of Zn2+ based on the excited state intramolecular proton transfer (ESIPT) mechanism. The specific recognition ability of Probe-ITR to Zn2+ was tested using UV-VIS and fluorescence emission spectroscopy. The results demonstrated a rapid response within 40s upon addition of an appropriate amount of Zn2+ into the mixed solution of the target probe molecules (DMSO/PBS = 5/5). Under 365 nm ultraviolet light irradiation, the colorless solution changed to yellow-green fluorescence with a 150-folds increase in intensity. Furthermore, the detection limit for specific recognition of Zn2+ by the probe molecule is only 17.3 nmol/L, indicating high sensitivity. The practical application potential of the probe molecules was enhanced by employing on information storage and conducting cell imaging experiments.

A Julolidine Aldehyde Dansyl Hydrazine Schiff Base as Fluorescence Chemosensor for Zn2+ ions Recognition and its Application

The Schiff base fluorescent probe (Dz-Jul), containing julolidine aldehyde and dansyl hydrazine, was derived using a simple condensation. This chemosensor showed high selectivity towards Zn2+ and quick response (170 s) in DMSO/H2O solutions (8/2, v/v, pH 7.2 buffer). A fluorometric titration determined that Dz-Jul-Zn2+ has a binding ratio of 1:1, and the association constant (Ka) is 1.03 × 105 M-1. The Dz-Jul detection limit of Zn2+ ions was 15 nM, much lower than the WHO standard (76.0 nM). DFT, ESI mass, and FTIR spectral demonstrated a plausible complexation mode between Dz-Jul and Zn2+ ions. In actual water samples, Zn2+ has been detected with good detection performance using Dz-Jul. Additionally, Dz-Jul-coated test strips allowed for rapid and qualitative monitoring of Zn2+ ions in a visible manner.

Recent Advances in Organic Small-Molecule Fluorescent Probes for the Detection of Zinc Ions (Zn2+)

Zinc(II) ions (Zn2g) play crucial roles in the growth, propagation, and metabolism of animals, plants, and humans. Abnormal concentrations of Zn2+ in the environment and living organisms pose potential risks to environmental protection and human health. Therefore, it is imperative to develop rapid, reliable and in-situ detection methods for Zn2+ in both environmental and biological contexts. Furthermore, effective analytical methods are required for diagnosing diseases and understanding physiological metabolic mechanisms associated with Zn2+ concentration levels. Organic small-molecule fluorescent probes offer advantages such as fast, reliable, convenient, non-destructive detection capabilities and have significant application potential in Zn2+ detection and bioimaging; thus garnering extensive attention. Over the past two years alone, various organic small-molecule probes for Zn2+ based on different detection mechanisms and fluorophores have been rapidly developed. However, these probes still exhibit several limitations that need further resolution. In light of this context, we provide a comprehensive summary of the detection mechanisms, performance characteristics, and application scope of Zn2+ fluorescence probes since year 2022 while highlighting their advantages. We also propose solutions to address existing issues with these probes and outline future directions for their advancement. This review aims to serve as a valuable reference source offering insights into the development of advanced organic small-molecule-based fluorescence probes specifically designed for detecting Zn2+.

A single 8-hydroxyquinoline-appended bile acid fluorescent probe obtained by click chemistry for solvent-dependent and distinguishable sensing of zinc(II) and cadmium(II)

Construction of fluorescent probes for zinc ion (Zn2+ ) and cadmium ion (Cd2+ ) is significant for the safety of humans. However, the discriminating recognition of Zn2+ and Cd2+ by a single probe remains challenging owing to their similar properties. Herein, a novel deoxycholic acid derivative containing 8-hydroxyquinoline fluorophore has been facilely synthesized through click chemistry to form a clamp-like probe. Using its perfect bonding cavity from 1,2,3-triazole and quinoline, this molecule showed favorable solvent-dependent fluorescent responses and distinguished Zn2+ and Cd2+ in different solvents. In ethanol aqueous solution, it displayed good selectivity and ratiometric fluorescence to Zn2+ with 30 nm spectroscopic red-shifts. In acetonitrile aqueous solution, it exhibited good selectivity and ratiometric fluorescence to Cd2+ with 18 nm spectroscopic red-shifts. Moreover, the unique microstructural features of the probe in assembly were used to reflect its recognition processes. Due to its merits of low detection limit and instant response time, the probe was utilized for sensing Zn2+ and Cd2+ in water, beer and urine with high accuracy. Meanwhile, this probe served as a handy tool and was employed to obtain inexpensive test strips for the prompt and semiqualitative analysis of Zn2+ and Cd2+ with the naked eye.

Theoretical investigation of the Zn2+ detection mechanism based on the quinoline derivative of the Schiff-base receptor

The sensing mechanism of the quinoline-derived Schiff base HL (concentrated from 8-hydroxyquinoline with 2,4-dihydroxybenzaldehyde) as a highly selective fluorescent probe for Zn²⁺ was investigated by theoretical calculations with DFT and TDDFT. The conformations of the HL molecule, its ketone form and its Zinc complex structure, were optimized in the ground and excited states. The systems have been studied in depth in terms of structural parameters, frontier molecular orbitals, absorption and fluorescence spectra as well as potential energy curves analysis and approximately density gradient analysis. The present theoretical calculations propose a different detection mechanism from that proposed experimentally. The theoretical results predict that the fluorescence quenching in HL is attributed to the excited state intramolecular proton transfer (ESIPT) rather than the photoinduced electron transfer (PET) of benzene to electrons. When Zn²⁺ is introduced, Zn²⁺ takes the place of the H atom, creating a complex that blocks the ESIPT reaction and restores fluorescence.

Benzimidazole–acid hydrazide Schiff–Mannich combo ligands enable nano–molar detection of Zn2+ via fluorescence turn–on mode from semi–aqueous medium, HuH–7 cells, and plants

Herein, we have synthesized two unsymmetrical and dipodal Schiff–Mannich combo ligands, benzoic acid (3–benzoimidazol–1–ylmethyl–2–hydroxy–5–methyl–benzylidene)–hydrazide (H2BBH) and the hydroxyl analogue, 2–hydroxy–benzoic acid (3–benzoimidazol–1–ylmethyl–2–hydroxy–5–methyl–benzylidene)–hydrazide (H3BSH) for selective detection of Zn2+ in semi–aqueous...