A reversible CHEF-based NIR fluorescent probe for sensing Hg2+ and its multiple application in environmental media and biological systems

The effect of para-substituted benzaldehyde derivatives with push/pull electron groups on the conformation of bovine serum albumin and its toxicity investigation in Brachionus calyciflorus Pallas (rotifers)

As intermediates widely used in the synthesis of industrial compounds, excessive ingestion of 4-hydroxybenzaldehyde (4-HBzH) and 4-nitrobenzaldehyde (4-NBzH) may induce potentially irreversible damage in organisms. The potential toxicological of 4-HBzH and 4-NBzH were investigated through a multi-disciplinary approach involving density functional theory (DFT), multispectral techniques and molecular docking, with bovine serum albumin (BSA) employed as the model protein of the study. The interaction mechanism between 4-NBzH/4-HBzH and BSA involved static quenching, and the affinity of 4-NBzH for BSA was stronger than that of 4-HBzH as shown by the Ka value (4-NBzH: 6.30 × 104 M-1 ＞ 4-HBzH: 5.96 × 104 M-1), which is also confirmed by DFT calculations. The binding of 4-HBzH/4-NBzH to BSA is mainly through hydrogen bonding and hydrophobic interactions, to which van der Waals forces also contribute, as supported by molecular simulations. Furthermore, the toxicity test based on the Brachionus calyciflorus Pallas (Rotifers) showed that the LC50 of 4-NBzH (8.36 mg/L) was significantly lower than that of 4-HBzH (12.13 mg/L). Interestingly, the electron-withdrawing group-substituted benzaldehyde derivatives may be more hazardous than the electron donor-substituted benzaldehyde derivatives. The findings of this study elucidate toxicological information on the action of 4-HBzH/4-NBzH with BSA and rotifers and offer theoretical foundation for the prevention of the hazards from benzaldehyde derivatives.

A novel Cu2+-coordinated fluorescent sensing system for specific detection of glyphosate and its applications in environmental and biological systems

Glyphosate is a non-selective herbicide widely used in agriculture, and its overexposure poses significant health and environmental risks. Herein, a novel Cu2+-coordinated fluorescent sensing system (HYBC-Cu2+ system) based on acylhydrazone groups was designed, capable of glyphosate-specific recognition. The HYBC-Cu2+ system was constructed with simple steps, with the advantages of short recognition time (< 1 min), good specificity, anti-interference, and excellent sensitivity (LOD = 95 nM). The effect of proton functional group on glyphosate resulted in Cu2+ of the HYBC-Cu2+ system being able to be competed down by the glyphosate to release HYBC thus inducing the fluorescence enhancement of the system and realizing the rapid detection of glyphosate. The recognition mechanism by the HYBC-Cu2+ system was verified by high-resolution mass spectrometry (HRMS), density function theory (DFT) calculations and Job's Plot. The system can cycle alternately to detect the glyphosate more than 6 times and effectively quantify trace glyphosate in environmental samples. Furthermore, the HYBC-Cu2+ system has low cytotoxicity and good membrane permeability, which can enter HeLa cells and zebrafish to react rapidly with exogenous glyphosate, resulting in fluorescence enhancements that are visually distinctive. The application of HYBC-Cu2+ system can further promote the development of pesticide residue monitoring methods such as glyphosate and provide scientific basis for policy making and public health protection.

A reversible fluorescence probe enables bioimaging and toxicity evaluation of lithium ion in living human cells

The extensive use of lithium (Li) in green energy generation and storage poses a growing risk of human Li+ exposure. Therefore, advancing bioimaging and safety evaluation approaches for Li+ is crucial. This study introduces a new stratagem to reveal the toxicity effects of Li+ by developing a reversible lithium-sensitive probe (LSP). This probe, designed by conjugating spiropyran and azacrown ethers, enables highly selective imaging of Li+ within living cells at environmentally relevant concentrations, both extracellularly and in vitro. Utilizing this advanced probe, we conducted noninvasive monitoring to observe Li+ permeation through Aquaporin-1 (AQP1) channels in human embryonic kidney cells (HEK293) and its subsequent accumulation in the mitochondria. This mitochondrial accumulation led to decreased mitochondrial membrane potential, increased Cytochrome C (Cyto C) release, disruption of mitochondrial respiratory chain complex activity, and heightened cellular oxidative stress. These findings underscore LSP's utility in delineating spatial distributions and concentrations of Li+ in biological systems and monitor the Li+-involved nephrotoxicity caused by mitochondrial damage.

Selenophene-containing silicon-rhodamine: A novel near-infrared fluorescent probe for Hg2+ detection and its application in cell imaging

Monitoring of mercury ion (Hg2+) pollution is one of the eternal themes due to its notorious toxicity. Herein, we elaborately designed a novel fluorescent probe N'-((selenophen-2-yl)methylene)Si-rhodamine B hydrazide (Se-SiRH) by integrating 2-formylselenophene with Si-rhodamine B hydrazide. Se-SiRH exhibited an excellent near-infrared response towards Hg2+ in MeOH/PBS solution (1:1, v/v, pH = 7.0) and superior specificity towards Hg2+ than other metal ions. Meanwhile, striking sensitivity towards Hg2+ was found and the limit of detection in fluorescence measurement was calculated to be 2.1 × 10-9 mol·L-1. What's more, Hg2+-binding mechanism was confirmed with Job-plot measurement, HR-MS and theoretical calculation. Importantly, the success in detecting Hg2+ in real water samples and visualizing Hg2+ in HepG2 cells validated its eye-catching application capability in environmental and biological research.

A Rhodamine-based high-sensitivity low-cytotoxicity probe for rapid turn-on detection of Hg2

By integrating Rhodamine B and 4-phenylmorpholine moieties, a novel fluorescent probe named RhPy is synthesized for detecting Hg2+. Its recognition mechanism involves the reaction of Hg2+ with dithiooxamide, ultimately triggering the opening of the Rhodamine spirolactam and forming a new molecule RhPy-S with strong emission. The probe exhibits impressive limit of detection (0.015 μM) and short response time (<10 s). Importantly, RhPy shows almost none-cytotoxicity and RhPy-S has the emission spectrum peaking at 596 nm, which endow the probe with a good tissue penetration ability and practical utility in living cells, zebrafish and in vivo mice models. This work advances the field by providing a highly sensitive chemosensor for both environmental and biological applications.

Fluorescent Carbon Dots: Aggregation-Induced Emission Enhancement, Application as Probe for CN- and Cr2O7-2, Sensing Strips and Bio-imaging Agent

Fluorescent carbon dots (Trp-CDs) were prepared using tryptophan as precursor and were characterized on the basis of elemental analysis, powder-XRD, IR, Raman spectroscopy, 13C-NMR, UV-Vis, fluorescence and TEM. Trp-CDs exhibit poor fluorescence in 100% water but showed strong Aggregation Induced Emission (AIE) in ethanol and higher alcohols. The anion sensing study of Trp-CD revealed that it selectively detects CN- and Cr2O7-2 and from fluorescence quenching titration study, quenching constant, LOD and range of detection were evaluated. The emission life-time of Trp-CD before and after addition of CN- and Cr2O7-2 were measured, the decay curve before addition of anion was best fitted with a bi-exponential function with life-time of τ1 2.79 ns (10.74%) and τ2 18.93 ns (89.26%). The mechanistic study revealed that for CN-, the fluorescence quenching is due to its interaction with protons attached to surface functional groups and for Cr2O7-2, it is due to inner filter effect (IFE). Sensing strips were prepared by coating Trp-CDs onto various solid surfaces including agarose films and were used for detection of CN- and Cr2O7-. Trp-CD was found to be nontoxic and biocompatible and used as staining agent for Artemia and Bacteria (Bacillus Subtilis, Pseudomonas) and detection of CN- and Cr2O7-.

Proteomic and spectral analysis reveals the role of extracellular polymeric substances in mercury biosorption by activated sludge under high-altitude conditions

In high-altitude regions, elevated mercury (Hg) levels in wastewater treatment plants (WWTPs) influent raise concerns about treatment efficiency and environmental impact. This study investigated the Hg biosorption capacity of activated sludge under high-altitude conditions, focusing on the binding mechanisms between EPS and Hg, and variations in EPS secretion. Low pressure, oxygen, and temperature at high altitudes increase EPS secretion, enhancing Hg biosorption. EPS provides numerous binding sites for Hg, forming nonfluorescent complexes with tryptophan-like and aromatic proteins, while hydrocarbon and oxygen-containing groups limit Hg entry into microbial cells. Proteomic analysis revealed the upregulation of transporters, stress-resistance, and binding proteins, along with those involved in carbon and amino acid metabolism, which enhance microbial resilience and EPS production, leading to increased Hg biosorption. These insights reveal adaptive mechanisms that optimize pollutant removal in high-altitude environments.

Near-infrared fluorescent probe visual detection of Hg2+ and its application in biological system and ecological system

Mercury ion (Hg2+), a heavy metal cation with greater toxicity, is widely present in the ecological environment and has become a serious threat to human health and environmental safety. Currently, developing a solution to simultaneously visualize and monitor Hg2+ in environmental samples, including water, soil, and plants, remains a great challenge. In this work, we created and synthesized a near-infrared fluorescent probe, BBN-Hg, and utilized Hg2+ to trigger the partial cleavage of the carbon sulfate ester in BBN-Hg as a sensing mechanism, and the fluorescence intensity of BBN-Hg was significantly enhanced at 650 nm, thus realizing the visualization of Hg2+ with good selectivity (detection limit, 53 nM). In live cells and zebrafish, the probe BBN-Hg enhances the red fluorescence signal in the presence of Hg2+, and successfully performs 3D imaging on zebrafish, making it a powerful tool for detecting Hg2+ in living systems. More importantly, with BBN-Hg, we are able to detect Hg2+ in actual water samples, soil and plant seedling roots. Furthermore, the probe was prepared as a test strip for on-site determination of Hg2+ with the assistance of a smartphone. Therefore, this study offers an easy-to-use and useful method for tracking Hg2+ levels in living organisms and their surroundings.

A turn-on anthraquinone-derived colorimetric and fluorometric dual-mode probe for highly selective Hg2+ determination and bioimaging in living organisms

Mercury ion (Hg2+) is considered a harmful neurotoxin, and real-time monitoring of Hg2+ concentrations in environmental and biological samples is critical. Fluorescent probes are a rapidly emerging visualization tool owing to their simple design and good selectivity. Herein, a novel fluorescence (FL) probe 2-(4-((6-((quinolin-8-yloxy)methyl)pyridin-2-yl)methyl)piperazin-1-yl)anthracene-9,10-dione (QPPA) is designed using piperazine as a linker between the anthraquinone group, which serves as a fluorophore, and N4O as the Hg2+ ligand. The probe exhibits FL "turn-on" sensing of Hg2+ because the complex inhibits the photo-induced electron transfer (PET) process. Moreover, QPPA can overcome the invasion by other possible cations, resulting in a clear color change from orange to colorless with the addition Hg2+. The chelation of QPPA with Hg2+ in a 1:1 ratio. Subsequently, the theoretically determined binding sites of the ligand to Hg2+ are validated through 1H NMR titration. The in situQPPA-Hg2+ complex can be subjected to Hg2+ extraction following the introduction of S2- owing to its robust binding capacity. The exceptional limit of detection values for Hg2+ and S2- are obtained as 63.0 and 79.1 nM (S/N = 3), respectively. Moreover, QPPA can display bright red FL in the presence of Hg2+ in different biological specimens such as HeLa cells, zebrafish, onion root tip tissues, and water flea Daphnia carinata, further providing an effective strategy for environmental monitoring and bioimaging of Hg2+ in living organisms.

Aggregation-Induced Emission Active Benzidine-Pyridoxal Derived Scaffold for Detecting Fe3+ and pH

Present work introduces an aggregation-induced emission (AIE) active Schiff base 4,4'-((1E,1'E)-([1,1'-biphenyl]-4,4'-diylbis(azaneylylidene))bis(methaneylylidene))bis(5-(hydroxymethyl)-2-methylpyridin-3-ol) (BNPY). Schiff base BNPY was synthesized by reacting benzidine with pyridoxal. The non-fluorescent BNPY in freely soluble DMSO medium showed a significant fluorescence enhancement at 563 nm (λex = 400 nm) upon increasing the water fraction (fw) in DMSO above 60% due to the restriction of intramolecular rotation upon the aggregation of BNPY. The AIE active BNPY was employed for the detection of metal ions in DMSO:H2O (fw = 70%). Upon the addition of Fe3+, the fluorescence emission of BNPY at 563 nm was quenched due to the chelation-enhanced fluorescence quenching (CHEQ). The Job's plot experiment supported the formation of a complex between BNPY and Fe3+ in 1:2 binding ratio. With an estimated detection limit of 5.6 × 10-7 M, BNPY was employed to detect and quantify Fe3+ ion in real water samples with satisfactory recovery percentages. Moreover, the pH studies of BNPY aggregates revealed three different fluorescence windows: non-fluorescent in acidic pH 2.02 to 3.16, yellow fluorescent between pH 3.60 to 9.33, and green fluorescent in basic pH 9.96 to 12.86.

Enantioselective effects of chiral profenofos on the conformation for human serum albumin

Profenofos, as a typical chiral organophosphorus pesticide, can cause various environmental problems and even endanger human health when used in excess. The toxicity of chiral profenofos was investigated through multispectral analysis, molecular docking, and density functional theory (DFT), employing human serum albumin (HSA) as the model protein. Fluorescence titration and lifetime measurements demonstrated that the interaction between chiral profenofos and HSA involves static quenching. Chiral profenofos forms a 1:1 complex with HSA at site II (subdomain IIIA), primarily driven by hydrophobic interactions and hydrogen bonds. Notably, the binding efficacy diminishes as temperature increases. Spectroscopic analyses confirm that chiral profenofos alters the microenvironment and structure of HSA, with the R-enantiomer exerting a greater impact than the S-enantiomer. Consequently, the toxicological implications of the R-profenofos is significantly more pronounced. Investigating the molecular-level toxic effects of chiral pesticides enhances the thoroughness of pesticide assessments, aids in understanding their distribution, metabolism, and associated risks, and facilitates the development of mitigation strategies.

Engineering a far-red fluorescent probe for rapid detection of Hg(II) ions in both cells and zebrafish

Abnormal accumulation of mercury ions (Hg2+) in organisms can lead to severe central nervous system and other diseases. Therefore, the monitoring and detection of Hg2+ are of great significance for human health and environmental safety. Herein, we designed and synthesized a novel far-red to NIR emission fluorescent probe (Rho-Hg) based on rhodamine derivative as the fluorophore and thiospirolactone as the recognition site for turn-on detecting of Hg2+ in living cells and zebrafish. The probe Rho-Hg displayed superior sensitivity (detection limit = 17.5 nM), rapid response (<1 min), colorimetric change, high selectivity, and moderate pH stability. Leveraging this probe, we realized the real-time monitoring of Hg2+ in real samples, living cells and zebrafish. By fostering zebrafish embryos and larvae in Hg2+-containing nutrient solution, we noticed that Hg2+ was ingested into the zebrafish liver when zebrafish were grown up to 3 days old, and thus we successfully monitored the accumulation and changes of Hg2+ during zebrafish growth and development. Thus, the probe Rho-Hg could be a powerful tool for sensitive and real-time monitoring of Hg2+ in living systems.

Real time monitoring of nerve agent mimics: Novel solid state emitter for enhanced precision and reliability

Chemical nerve agents are hazardous compounds that terrorists can exploit to pose a significant threat to public safety and national security. The nucleophilic behaviour of these agents enables their interaction with acetyl cholinesterase in the body, leading to paralysis and potentially fatal consequences. Therefore, developing robust and efficient detection methods for these agents is crucial for preventing their misuse. In this manuscript, (E)-12-(1-hydrazineylideneethyl)benzo[f]pyrido[1,2-a]indole-6,11-dione (HBID) is developed as a novel colorimetric and fluorometric probe for the detection of specific chemical nerve agent simulants in both liquid and vapor phase. HBID reacts rapidly with diethyl chlorophosphate (DCP), a common nerve agent simulant, leading to a significant increase in the fluorescence intensity. Under optimized conditions, HBID exhibits high sensitivity, good recyclability, fast response and low limit of detection (0.092 µM). NMR and mass spectral studies suggest that the reaction involves the nucleophilic addition of HBID to DCP, forming a phosphate ester. Additionally, the developed sensor demonstrates viscosity-sensitive AIE phenomena thus greatly expanding its potential applications in biological systems. This sensitivity enables precise detection and visualization of viscosity changes within cellular environments, making the sensor an invaluable tool for studying complex biological processes. The developed probe also detects pH within biologically relevant range (4-6). In practical applications, the probe-treated strips efficiently detected DCP vapor in real time, showing a noticeable fluorescence response. Further, the probe has a strong potential to detect the presence of DCP in the soil samples.

A novel "Turn-Off-On" fluorescent probe for specific sequential detection of Cu2+ and glyphosate and its application in biological imaging

As common pollutants, Cu2+ and glyphosate pose a serious threat to human health and the ecosystem. Herein, a fluorescent probe (E)-7-(diethylamino)-N'(4-(diethylamino)-2-hydroxybenzyl)-2-oxo-2H chromophore-3-carbazide (DDHC) was designed and synthesised for the sequential recognition of Cu2+ and glyphosate. DDHC has the advantages of a short synthesis path, easy-to-obtain raw materials, good anti-interference ability, and strong stability. The interaction of the DDHC-Cu2+ complexes with glyphosate allows the amino and carboxyl groups in glyphosate molecules to coordinate with Cu2+ strongly, competing for the Cu2+ in the DDHC-Cu2+ complexes and releasing the DDHC, leading to the recovery of fluorescence. The recognition was further validated through Job's plot, HRMS, and DFT calculations. In addition, the successful recovery of Cu2+ and glyphosate in different environmental water samples fully demonstrates the practical application potential of DDHC. Especially, DDHC has low cytotoxicity and can enter zebrafish and HeLa cells, rapidly reacting with Cu2+ and glyphosate in the body, generating visible fluorescence quenching and recovery phenomena, achieving real-time visual monitoring of exogenous Cu2+ and glyphosate in zebrafish and HeLa cells. The targeting and dual selectivity of DDHC greatly enhance its potential application value in the field of detection, providing important theoretical support for studying the fate of multiple pollutants in the environment.

A novel red-to-near-infrared AIE fluorescent probe for detection of Hg2+ with large Stokes shift in plant and living cells

Due to the highly toxic nature of mercury ions to living organisms, accurately detecting Hg2+ in water samples and biological systems is of great significance. In this study, we designed and synthesized a novel red-to-near-infrared Aggregation-Induced Emission (AIE) fluorescent probe (named as DS) based Fluorene derivatives on specifically for Hg2+ detection. Probe DS can visually identify Hg2+ through an red-to-near-infrared fluorescence enhancement change, characterized by a large Stokes shift (130 nm) and AIE feature. This probe offers a fast response, high selectivity and sensitivity. The Hg2+-induced deprotection reaction of the thioketal mechanism was thoroughly investigated using nuclear magnetic resonance spectroscopy (NMR), mass spectrometry (MS) and density functional theory (DFT) calculation. Additionly, dynamic light scattering (DLS) results indicated that the aggregation states changes of the molecular play a crucial role in the AIE fluorescence response of probe DS toward Hg2+. The red-to-near-infrared response with AIE feature not only avoids the interference of auto-fluorescence signals in complex environments, but also reduces the fluorescence quenching caused by probe molecular aggregation. This makes probe DS highly suitable for high-quality imaging detection of Hg2+ in aqueous environments. Furthermore, probe DS demonstrates the capability for visual fluorescence detection of Hg2+ concentrations in water sample, plant roots and living cells.

Theoretical and experimental investigation of novel quinazoline derivatives: synthesis, photophysical, reactive properties, molecular docking and selective HSA biointeraction

Two new quinazoline derivatives (2a and 2b) were successfully synthesized in this work using the condensation technique in excellent yields. Using spectroscopic techniques and elemental analyses, the compounds were completely characterized. Density functional theory (DFT) computations have been used to examine the title compound's reactive characteristics. Chemical reactivity was predicted using local reactive descriptors and molecule electrostatic potential. Additionally, Time dependent DFT (TD-DFT) simulations were used to examine the impact of solvents on the photophysical characteristics. The affinity of compounds 2a and 2b for human serum albumin (HSA) was further explored using several electronic spectroscopies. Through static mechanisms, both compounds reduce the intrinsic fluorescence of HSA. It is determined that the HSA-2b complex's binding constant is significantly greater than the HSA-2a complex. The fluorescence spectrum measurements proved that the HSA underwent structural changes after interaction with these compounds. It was demonstrated by site marker competitive displacement studies that compounds 2a and 2b preferred to bind to site I in HSA subdomain IIA. Additionally, synchronised fluorescence spectra were utilized to analyze how HSA's conformation changed after interacting with various substances. The molecular docking investigations of these compounds with the three critical HSA binding sites, comprising subdomains IIA, IIIA, and IB, further confirmed the experimental findings. The significant contact between the investigated compounds and HSA was supported by the docking simulations.Communicated by Ramaswamy H. Sarma.

Multiple Applications of a Novel Fluorescence Probe with Large Stokes Shift and Sensitivity for Rapid H2S Detection

Herein, a novel fluorescence probe Fla-DNP based on flavonol has been designed and synthesized for rapid, specific detection of H2S. With the addition of H2S, Fla-DNP triggered thiolysis and released Fla displaying the "turn-on" fluorescence response at 566 nm, which is consistent with the reaction site predicted by calculating Electrostatic potential and ADCH charges. As an easily available H2S probe, Fla-DNP has the advantages of high selectivity, anti-interference, low detection limit (0.834 μM), short response time (6 min), and large Stokes shift (124 nm). The sensing mechanism of H2S was determined by HRMS analysis and DFT calculation. Moreover, Fla-DNP processes a wide range of multiple applications, including the detection of H2S in environmental water samples with good recovery rates ranging from 89.6% to 102.0%, as well as tracking the production of H2S during food spoilage. Meanwhile, the probe exhibits superior biocompatibility and can not only be available used for H2S detection in living cells but be further designed as an H2S-activated CO photoreleaser, based on which it can be developed as a targeted anti-cancer drug.

Influence of para-substituted benzaldehyde derivatives with different push/pull electron strength groups on the conformation of human serum albumin and toxicological effects in zebrafish

Excessive intake of benzaldehyde and its derivatives can cause irreversible damage to living organisms. Hence, benzaldehyde derivatives with different para-substitutions of push/pull electronic groups were chosen to investigate the effect of different substituent properties on the structure of human serum albumin (HSA). The binding constants, number of binding sites, major interaction forces, protein structural changes, and binding sites of benzaldehyde (BzH) and its derivatives (4-BzHD) with HSA in serum proteins were obtained based on multispectral and molecular docking techniques. The mechanism of BzH/4-BzHD interaction on HSA is mainly static quenching and is accompanied by the formation of a ground state complex. BzH/4-BzHD is bound to HSA in a 1:1 stoichiometric ratio. The interaction forces for the binding of BzH/4-BzHD to HSA are mainly hydrogen bonding and hydrophobic interaction, which are also accompanied by a small amount of electrostatic interactions. The effect of BzH/4-BzHD on HSA conformation follows: 4-Diethylaminobenzaldehyde (4-DBzH) > 4-Nitrobenzaldehyde (4-NBzH) > 4-Hydroxybenzaldehyde (4-HBzH) > 4-Acetaminobenzaldehyde (4-ABzH) > BzH, which means that the stronger push/pull electronic strength of the para-substituted benzaldehyde derivatives has a greater effect on HSA conformation. Furthermore, the concentration-lethality curves of different concentrations for BzH/4-BzHD on zebrafish verified above conclusion. This work provides a scientific basis for the risk assessment of benzaldehyde and its derivatives to the ecological environment and human health and for the environmental toxicological studies of benzaldehyde derivatives with different strengths of push/pull electron substitution.

Difunctional Fluorescent Probes for Iron and Hydrogen Sulfide Detection Based on Diphenyl Derivative

In order to better monitor the content of Fe3+ and H2S in the biological environment, two new fluorescent probes were designed and synthesized. With the addition of Fe3+, the strong fluorescence emission of two probes was significantly quenched due to the paramagnetic effect of Fe3+. With the further addition of S2-, the fluorescence intensity was quickly restored. Two probes showed high selectivity and strong sensitivity for the detection of Fe3+ and S2-, and the fluorescence intensity "ON-OFF-ON" was accompanied with the interaction process. At the same time, two probes displayed good anti-interference ability which was not interfered by the existence of other ions. In addition, two probes illustrated fast response time to Fe3+, S2- and small cytotoxicity to cells. Therefore, two probes can provide a potential ideal tool for detecting Fe3+ and H2S in organisms and the environment.

Copper(II) Driven Fluorescence switch-on Detection of Ovalbumin and GSH Using a Pyridoxal 5'-phosphate Derived Tetradentate Schiff Base and its Applications

The facile detection of glutathione (GSH) and ovalbumin (OVA) is of great importance in biological research. Herein, a tetradentate Schiff base N, N'-bis(pyridoxal-5-phosphate)-o-phenylenediamine (L) obtained by condensing two moles of pyridoxal 5'-phosphate (PLP) with one mole of 1,2-phenylenediamine was employed for the fluorescence switch-on detection of GSH and OVA. When excited at 389 nm, receptor L showed a weak emission at 454 nm in an aqueous medium. The addition of GSH to the solution of L caused a significant fluorescence enhancement at 454 nm. Amino acids (leucine, glycine, serine, tryptophan, homocysteine, alanine, methionine, arginine and proline) and albumins (bovine serum albumin and OVA) failed to alter the fluorescence profile of L. Receptor L can be applied to detect GSH down to 1.16 µM. However, the fluorescence emission of L was quenched upon the formation of the L-Cu2+ complex. The addition of GSH and OVA to the in-situ formed L-Cu2+ complex restored not only the fluorescence emission of L but also a noticeable fluorescence enhancement observed at 454 nm. The decomplexation of L-Cu2+, along with the interaction of L with GSH and OVA is expected to suppress the conformational flexibility of L that enhanced the fluorescent intensity at 454 nm. Using L-Cu2+ complex, the concentration of OVA and GSH can be detected down to 0.31 µM and 0.20 µM, respectively. Molecular docking and dynamics simulation were performed to analyze the binding mode, conformational flexibility and dynamic stability of the L-Cu2+-OVA complex. Finally, the analytical novelty of L-Cu2+ was examined by detecting GSH/OVA in real biological samples, such as human blood serum, urine, and egg white.

A novel Zn2+-coordination fluorescence probe for sensing HPPD inhibitors and its application in environmental media and biological imaging

Mesotrione, topramezone, tembotrione, and sulcotrione are four types of 4-hydroxyphenylpyruvate dioxidase (HPPD) inhibitor herbicides that are extensively employed in agricultural practices, but their usage also leads to environmental pollution and poses risks to human health. A probe (E)-1-((2-(pyridin-2-yl) hydrazineylidene) methyl) naphthalen-2-ol (CHMN) based on chelation enhancement (CHEF) effect synthesized. CHMN was first chelated with Zn2+ to form a probe system with green, which can be further used to detect mesotrione, topramezone, tembotrione and sulcotrione in complicated environment. CHMN-Zn2+ detection of four pesticides was accurate, with an excellent linear relationship between 0 and 100 μM. The detection limits were LODmesotrione = 7.79 μM, LODtopramezone = 1.91 μM, LODtembotrione = 1.38 μM and LODsulcotrione = 2.43 μM. The detection time is 1 min, and it is successfully applied in real water sample and bioimaging. This work can provide a novel method for studying the migration and behavior of environmental pollutants.

Thin colorimetric film array for rapid and selective detection of v-type nerve agent mimic in potentially contaminated areas

The expeditious detection and quantification of V-series nerve agents (VX) on potentially contaminated surfaces are crucial for the prevention of regional conflict incidents, acts of terrorism, or illicit activities. However, the low volatility and high toxicity of VX make these tasks challenging. Herein, we designed two novel colorimetric thin polymeric films to rapidly and sensitively detect demeton-S, a VX mimic, in contaminated areas. The polymeric films were specifically engineered to include a coordination site for Au (III) ions. Initially, these films were coordinated with Au (III), causing a discernible alteration in color due to enhancement in intramolecular charge transfer process. In the presence of demeton-S, the Au (III) ligands in the films are displaced with demeton-S, resulting in the restoration of the original color of the film, as the enhanced intramolecular charge transfer process is inhibited and thereby serving as an indicator of the presence of demeton-S. The polymeric films exhibit remarkable selectivity toward demeton-S compared to G-type nerve agents and other interference. The reusability of the polymeric films for demeton-S detection was achieved owing to the reversibility of the films during the alternative exposure of Au (III) and demeton-S. The polymeric films demonstrated their applicability for demeton-S detection and quantification in several contaminated areas, including different water, soil, and skin, rendering them highly suitable for on-site measurements.

A Chalcone-based Fluorescence Probe for H2S Detecting Utilizing ESIPT Coupled ICT Mechanism

The accurate and effective identification of hydrogen sulfide holds great significance for environmental monitoring. Azide-binding fluorescent probes are powerful tools for hydrogen sulfide detection. We combined the 2'-Hydroxychalcone scaffold with azide moiety to construct probe Chal-N3, the electron-withdrawing azide moiety was utilized to block the ESIPT process of 2'-Hydroxychalcone and quenches the fluorescence. The fluorescent probe was triggered with the addition of hydrogen sulfide, accompanied by great fluorescence intensity enhancement with a large Stokes shift. With excellent fluorescence properties including high sensitivity, specificity selectivity, and wider pH range tolerance, the probe was successfully applied to natural water samples.

In-lab synthesized turn-off fluorescence sensor for estimation of Gemigliptin and Rosuvastatin polypill appraised by Spider diagram, AGREE and whiteness metrics

Gemigliptin-Rosuvastatin single-pill combination is a promising therapeutic tool in the effective control of hyperglycemia and hypercholesterolemia. Organic sensors with high quantum yields have profoundly significant applications in the pharmaceutical industry, such as routine quality control of marketed formulations. Herein, the fluorescence sensor, 2-Morpholino-4,6-dimethyl nicotinonitrile 3, (λex; 226 nm, λem; 406 nm), was synthesized with a fluorescence quantum yield of 56.86% and fully characterized in our laboratory. This sensor showed high efficiency for the determination of Gemigliptin (GEM) and Rosuvastatin (RSV) traces through their stoichiometric interactions and simultaneously fractionated by selective solvation. The interaction between the stated analytes and sensor 3 was a quenching effect. Various experimental parameters and the turn-off mechanism were addressed. The adopted approach fulfilled the ICH validation criteria and showed linear satisfactory ranges, 0.2-2 and 0.1-1 μg/mL for GEM and RSV, respectively with nano-limits of detection less than 30 ng/mL for both analytes. The synthesized sensor has been successfully applied for GEM and RSV co-assessment in their synthetic polypill with excellent % recoveries of 98.83 ± 0.86 and 100.19 ± 0.64, respectively. No statistically significant difference between the results of the proposed and reported spectrophotometric methods in terms of the F- and t-tests. Ecological and whiteness appraisals of the proposed study were conducted via three novel approaches: the Greenness Index via Spider Diagram, the Analytical Greenness Metric, and the Red-Green-Blue 12 model. The aforementioned metrics proved the superiority of the adopted approach over the previously published one regarding eco-friendliness and sustainability. Our devised fluorimetric turn-off sensing method showed high sensitivity, selectivity, feasibility, and rapidity with minimal cost and environmental burden over other sophisticated techniques, making it reliable in quality control labs.

Myricetin-based fluorescence probes with AIE and ESIPT properties for detection of hydrazine in the environment and fingerprinting

BACKGROUND

Hydrazine (N2H4) is a highly toxic and versatile chemical raw material, which poses a serious threat to the environment and human health when used in large quantities. However, the traditional methods for the detection of N2H4 have the disadvantages of time-consuming, complicated operation and expensive instruments. In contrast, fluorescence probes have many advantages, such as simple operation, high sensitivity, good selectivity, and fast response time. Therefore, there is an urgent need for a fluorescence probe that can rapidly and accurately detect the presence of N2H4 and monitor the changes in its concentration.

RESULTS

For this purpose, we designed and synthesized a series of myricetin fluorescence probes 3-(substituent group)-5,7-dimethoxy-4-oxo-2-(3,4,5-trimethoxy. phenyl)-4H-chromen-4-one (Myr-R) for N2H4 detection. In the presence of N2H4, the probe 5,7-dimethoxy-3-(2,3,4,5,6-pentafluorobenzoate)-2-(3,4,5-trimethoxyphen-yl). -4H-chr-omen-4-one (Myr-3) shows significant fluorescence changes, double emission properties and a large Stokes shift (183 nm), and exhibits high selectivity and sensitivity to N2H4 (The detection limit is 93 nM). Importantly, the qualitative and quantitative analysis of N2H4 in water, soil, and air can be accomplished using fluorescence, smartphone, and UV lamps coupled with Myr-3. In addition, Myr-3 can be used for monitoring and imaging intracellular N2H4. Meanwhile, the fluorophore 3-hydroxy-5,7-dimethoxy-2-(3,4,5-trimethoxyphenyl)-4H-benzopyran-4-one (Myr-Me) was applied to fingerprinting of different substrate materials due to the fact that it exhibits strong yellow fluorescence emission in the solid state and shows excellent contrast and high resolution.

SIGNIFICANCE

The probe Myr-3 is not only able to rapidly detect N2H4 in complex environments, but also can be used for imaging intracellular N2H4. In addition, the fluorophore Myr-Me can be used as an effective imaging agent for visual fingerprinting. These properties enable the probe Myr-3 and the fluorophore Myr-Me for a wide range of potential applications in related fields.

Xanthene-based Hg2+ fluorescent probe for detection of Hg2+ in water/food samples, as well as imaging of live cells, zebrafish and tobacco seedlings

In this paper, an Hg2+ detection probe, HOS, was prepared with a xanthene as the parent fluorophore. Hg2+-initiated thioacetal deprotection reaction is the detection mechanism of this probe. After testing, the probe HOS was able to accurately determine Hg2+ with a detection limit of 36 nM. It was successfully applied to the detection of Hg2+ in different water samples and shrimp samples, meanwhile, the filter paper strips prepared by HOS were obviously changed from light yellow to dark yellow under daylight, and from green to yellow under 365 nm UV light. Furthermore, probe HOS enabled Hg2+ bioimaging experiments on HepG2 cells, zebrafish and tobacco seedlings under laser confocal microscopy.

Binding divergence of polystyrene nanoparticles with serum albumin caused by surface functionalization

Using a combination of spectroscopy, we devised an integrated structural strategy to comprehensively profile the molecular details of the impact of differently functionalized (plain, aminated, and carboxylated) polystyrene nanoparticles (PSNPs) on human serum albumin (HSA). The binding isotherms obtained from fluorescence and UV-vis absorption measurements demonstrate that surface functionalization can distinguish the interaction of PSNPs with HSA. Three-dimensional fluorescence and circular dichroism analysis of the effect of interaction with PSNPs on the native conformation and secondary structures of the protein reveals a diminution in the skeleton structure of HSA induced by the PSNPs. In accordance with this, it is discovered that the esterase activity of protein-PSNPs aggregates is diminished compared to that of the native protein. The carboxylated PSNPs exhibited the strongest protein binding and perturbation effects compared to other particles. Plain PSNPs exhibited significant hydrophobic interaction properties, as evidenced by spectral blue shifts and a diminished Stokes shift in the three-dimensional fluorescence assay. Our results exclusively highlight that the hydrophobic and surface charge characteristics of PSNPs govern the extent of interaction with the protein, which is beneficial to understanding microplastic toxicology.

Enantioselective effects of chiral prothioconazole and its metabolites: Oxidative stress in HepG2 cells and lysozyme activity

Chiral pesticides may exhibit enantioselectivity in terms of bioconcentration, environmental fate, and reproductive toxicity. Here, chiral prothioconazole and its metabolites were selected to thoroughly investigate their enantioselective toxicity and mechanisms at the molecular and cellular levels. Multispectral techniques revealed that the interaction between chiral PTC/PTCD and lysozyme resulted in the formation of a complex, leading to a change in the conformation of lysozyme. Meanwhile, the effect of different conformations of PTC/PTCD on the conformation of lysozyme differed, and its metabolites were able to exert a greater effect on lysozyme compared to prothioconazole. Moreover, the S-configuration of PTCD interacted most strongly with lysozyme. This conclusion was further verified by DFT calculations and molecular docking as well. Furthermore, the oxidative stress indicators within HepG2 cells were also affected by chiral prothioconazole and its metabolites. Specifically, S-PTCD induced more substantial perturbation of the normal oxidative stress processes in HepG2 cells, and the magnitude of the perturbation varied significantly among different configurations (P > 0.05). Overall, chiral prothioconazole and its metabolites exhibit enantioselective effects on lysozyme conformation and oxidative stress processes in HepG2 cells. This work provides a scientific basis for a more comprehensive risk assessment of the environmental behaviors and effects caused by chiral pesticides, as well as for the screening of highly efficient and less biotoxic enantiomeric monomers.

Investigating sulfonamides - Human serum albumin interactions: A comprehensive approach using multi-spectroscopy, DFT calculations, and molecular docking

The environmental and health risks associated with sulfonamide antibiotics (SAs) are receiving increasing attention. Through multi-spectroscopy, density functional theory (DFT), and molecular docking, this study investigated the interaction features and mechanisms between six representative SAs and human serum albumin (HSA). Multi-spectroscopy analysis showed that the six SAs had significant binding capabilities with HSA. The order of binding constants at 298 K was as follows: sulfadoxine (SDX): 7.18 × 105 L mol-1 > sulfamethizole (SMT): 6.28 × 105 L mol-1 > sulfamerazine (SMR): 2.70 × 104 L mol-1 > sulfamonomethoxine (SMM): 2.54 × 104 L mol-1 > sulfamethazine (SMZ): 3.06 × 104 L mol-1 > sulfadimethoxine (SDM): 2.50 × 104 L mol-1. During the molecular docking process of the six SAs with HSA, the binding affinity range is from -7.4 kcal mol-1 to -8.6 kcal mol-1. Notably, the docking result of HSA-SDX reached the maximum of -8.6 kcal mol-1, indicating that SDX may possess the highest binding capacity to HSA. HSA-SDX binding, identified as a static quenching and exothermic process, is primarily driven by hydrogen bonds (H bonds) or van der Waals (vdW) interactions. The quenching processes of SMR/SMZ/SMM/SDX/SMT to HSA are a combination of dynamic and static quenching, indicating an endothermic reaction. Hydrophobic interactions are primarily accountable for SMR/SMZ/SMM/SDX/SMT and HSA binding. Competition binding results revealed that the primary HSA-SAs binding sites are in the subdomain IB of the HAS structure, consistent with the results of molecule docking. The correlation analysis based on DFT calculations revealed an inherent relationship between the structural chemical features of SAs and the binding performance of HSA-SAs. The dual descriptor (DD) and the electrophilic Fukui function were found to have a significant relationship (0.71 and -0.71, respectively) with the binding constants of HSA-SAs, predicting the binding performance of SAs and HSA. These insights have substantial scientific value for evaluating the environmental risks of SAs as well as understanding their impact on biological life activities.

Development of a Water-Soluble Fluorescent Probe Based on Natural Flavylium for Mercury(II) Ion Detection and Clinical Antidote Evaluation

The health hazard posed by Hg2+ makes it imperative to develop a fast and convenient means for detecting Hg2+ in water samples and living objects. While fluorescence sensing technology is considered a promising candidate, the poor water solubility and fluorescence quenching in aqueous solutions of most existing probes limit their practical application. To overcome this, we developed a natural flavylium-inspired fluorescent probe with excellent water solubility. Our probe demonstrated outstanding performance of high sensitivity (LOD = 0.47 nM), fast response (<10 min), and great selectivity for Hg2+. Notably, we validated its applicability in real water, urine samples, and living cells. Furthermore, the probe was successfully applied to evaluate the effectiveness of antidotes for clinical Hg2+ poisoning.

An efficient chitosan-naphthalimide fluorescent probe for simultaneous detection and adsorption of Hg2+ and its application in seafood, water and soil environments

As a virulent heavy metal ion, Hg2+ will lead to a serious threat to ecosystem and human health. In this work, we reported a chitosan-naphthalimide fluorescent probe CS-NA-ITC for specific recognition and efficient adsorption of Hg2+. CS-NA-ITC showed no fluorescence in solution state, while the fluorescence intensity increased obviously at the presence of Hg2+, accompanied by the fluorescence color becomes from colorless to bright yellow. It displayed favorable properties like low detection limit (73 nM), extensive pH detection range (5-10) and excellent anti-interference ability. The binding pattern of CS-NA-ITC to Hg2+ was verified by Job's plot, XPS analysis and FT-IR test. In addition, CS-NA-ITC was utilized to recognition of Hg2+ in actual water and soil samples and seafood products. Furthermore, the CS-NA-ITC hydrogel could be employed as an efficient Hg2+ adsorbent with good reusability, which adsorption ability was enhanced compared to chitosan hydrogel.

A fluorescent probe based on aptamer gold nanoclusters for rapid detection of mercury ions

The mercuric ion (Hg2+) is a hazardous pollutant that is widely distributed in living organisms, foods, and environments with highly toxic and bio-accumulative properties. In the present study, a fluorescent probe based on aptamer gold nanoclusters (apt-AuNCs) was prepared for the ultrasensitive detection of Hg2+ in food. The principle underlying the prepared probe was the quenching of the fluorescence of apt-AuNCs in the presence of Hg2+ due to the strong metallophilic interactions between the 5d10 centers of Hg2+ and Au+. Under optimal conditions, the proposed fluorescent probe exhibited a linear relationship with Hg2+ concentration within the range of 2-200 nM (R2 = 0.9960). In addition, the limit of detection (LOD) was 0.0158 nM, which is below the Chinese standard value of 25 nM for Hg2+ in food. Furthermore, the apt-AuNCs were applied to detect Hg2+ in spinach and crawfish samples, with recovery percentages of 91.99%∼108.06%, meaning that apt-AuNCs could be used as a promising probe to detect Hg2+ in complex food samples.

A naphthalimide functionalized fluoran with AIE effect for ratiometric sensing Hg2+ and cell imaging application

The pollution caused by mercury ions (Hg²⁺) poses a potential threat to public health. Therefore, monitoring Hg²⁺ concentration in the environment is necessary and significant. In this work, a naphthalimide functionalized fluoran dye NAF has been prepared, which shows a new red-shift in emission at 550 nm with the maximum intensity in a mixture of water-CH₃CN (v/v = 7/3) due to aggregating induced emission (AIE) effect. Meanwhile, NAF can be employed as a Hg²⁺ ions sensor, which displays a selective and sensitive response to Hg²⁺ ions by the reduced fluorescence of naphthalimide fluorophore and increased fluorescence of fluoran group, respectively, showing ratiometric fluorescence signal changes with more than 65-fold emission intensity ratio increase and naked eyes visible color change. In addition, the response time is fast (within 1 min) and the sensing can be conducted in a wide pH range (4.0-9.0). Moreover, the detection limit has been evaluated to be 5.5 nM. The sensing mechanism may be attributed to the formation of a π-extended conjugated system due to the Hg²⁺ ions-induced conversion of spironolactone to the ring-opened form, partially accompanied by the fluorescence resonance energy transfer (FRET) process. Significantly, NAF exhibits suitable cytotoxicity to living HeLa cells, which allows it to be utilized for ratiometric imaging of Hg²⁺ ions assisted by confocal fluorescence imaging.

Recent Development in Fluorescent Probes for the Detection of Hg2+ Ions

Mercury, a highly toxic heavy metal, poses significant environmental and health risks, necessitating the development of effective and responsive techniques for its detection. Organic chromophores, particularly small molecules, have emerged as promising materials for sensing Hg2+ ions due to their high selectivity, sensitivity, and ease of synthesis. In this review article, we provide a systematic overview of recent advancements in the field of fluorescent chemosensors for Hg2+ ions detection, including rhodamine derivatives, Schiff bases, coumarin derivatives, naphthalene derivatives, BODIPY, BOPHY, naphthalimide, pyrene, dicyanoisophorone, bromophenol, benzothiazole flavonol, carbonitrile, pyrazole, quinoline, resorufin, hemicyanine, monothiosquaraine, cyanine, pyrimidine, peptide, and quantum/carbon dots probes. We discuss their detection capabilities, sensing mechanisms, limits of detection, as well as the strategies and approaches employed in their design. By focusing on recent studies conducted between 2022 and 2023, this review article offers valuable insights into the performance and advancements in the field of fluorescent chemosensors for Hg2+ ions detection.

A highly selective and sensitive ICT-based Cu2+ fluorescent probe and its application in bioimaging

Cu²⁺ is an essential trace element for the organism, but its excess can also cause irreversible damage to the organism. As such, a "Turn-Off" fluorescent probe DPAP for the specific detection of Cu²⁺ was successfully constructed. DPAP exhibits large Stokes shift (120 nm), fast reaction speed (1 min), low detection limit (15.2 nM), low toxicity, and good cell permeability. Cu²⁺ quenches the fluorescence of DPAP by blocking its intramolecular charge transfer process to achieve the detection of Cu²⁺ and has been confirmed by HRMS, ¹H NMR and DFT calculations. Excitingly, the five-cycle detection of Cu²⁺ and the successful recovery of trace Cu²⁺ in environmental water samples fully demonstrate the potential of DPAP for practical applications. In particular, DPAP can observe the distribution and translocation patterns of exogenous Cu²⁺ in HeLa cells and zebrafish in real-time. This research concept has offered important theoretical support for the study of the environmental behavior of heavy metal ions.

Enantioselective effect of chiral prothioconazole on the conformation of bovine serum albumin

As a typical chiral triazole fungicide, the enantioselective toxicity of prothioconazole to environmental organisms is of increasing concern. Herein, the binding mechanism of chiral PTCs to BSA was investigated by multi-spectral technique and molecular docking. Fluorescence titration and fluorescence lifetime experiments fully established that quenching BSA fluorescence by chiral PTCs is static quenching and could spontaneously bind to BSA. Hydrophobic interactions dominate the binding process of chiral PTCs to BSA. Differently, although both chiral PTCs and BSA have a primary binding site, the difference in chiral isomerism leads to a stronger binding ability of S-PTC than R-PTC. Both configurations of PTC can change the conformation of BSA and induce changes in the microenvironment around its amino acid residues, and the effect of S-PTC is more significant. Overall, S-PTC exhibited a more substantial effect on BSA structure relative to R-PTC. That is, S-PTC may lead to more potent potential toxicological effects on environmental organisms. This study provides a comprehensive assessment of the environmental behavior of chiral pesticides and their potential toxicity to environmental organisms at the molecular level and provides a theoretical basis for the screening of highly effective and biologically less toxic enantiomers of chiral pesticides.