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The detection and monitoring of organophosphate pesticides in environmental samples are of paramount importance due to their potentially harmful effects on human health and ecosystems. In this study, we present the detection of paraoxon ethyl (POE), a widely used organophosphate pesticide, utilizing an electrochemical method. We synthesized graphene oxide-incorporated pyrochlore-type lanthanum stannate (La 2 Sn 2 O 7 @GO) as a sensing material for enhanced detection sensitivity and selectivity. The electrochemical detection of POE was performed using a glassy carbon electrode modified with the synthesized nanocomposite. The modified electrode La 2 Sn 2 O 7 @GO/GCE exhibited a remarkable electrochemical response towards POE, showing a significant reduction potential and an increase in the peak current compared to the bare and other modified electrodes. The proposed electrochemical method showed excellent detection sensitivity and selectivity for POE, with a linear response range of concentrations from 0.01 to 360 μM and a low detection limit (LDL) of 2.73 nM. The sensor also exhibited good stability and reproducibility, making it a promising tool for practical pesticide detection applications. The developed sensor offers a cost-effective, sensitive, and reliable platform for the rapid monitoring of organophosphate pesticides in environmental samples, contributing to the advancement of pesticide detection technologies and environmental protection efforts. • La 2 Sn 2 O 7 @GO nanocomposites with more active sites/edges were synthesized. • La 2 Sn 2 O 7 @GO possessed the rapid heterogeneous electron transfer towards POE. • The developed sensor detects the POE with a detection limit of 2.73 nM. • Practical analysis of prepared sensor shows good recoveries on food and environmental samples. [ABSTRACT FROM AUTHOR]

Glycosaminoglycans (GAGs) in the urine of Wistar rats, and on the surface of the epithelium and lamina propria of the bladder, were quantitatively assessed before and after acute intoxication with paraoxon or cyclophosphamide. Paraoxon was administered subcutaneously (s.c.) twice with an interval of 1 h to a final dose of 275 mg/kg; cyclophosphamide was administered intraperitoneally (i.p.) with a single dose of 100 mg/kg or to a final dose of 240 mg/kg (three times per 80 mg/kg every 12 h). GAGs on the surface of the epithelium and lamina propria of the urinary bladder of rats were quantitatively determined by Alcian blue dye staining. GAGs in the urine were determined spectrophotometrically with 1-9-dimethyl methylene blue. By 48–96 h after intoxication with either paraoxon or cyclophosphamide, statistically significant increases in the concentration of GAGs were obtained both for the tissues of the bladder and the urine of rats. Cyclophosphamide, in contrast to paraoxon, caused the development of hemorrhagic cystitis in the animals. The synthesis of GAGs is considered to be compensatory response to the toxic xenobiotics. [ABSTRACT FROM AUTHOR]

The usage of organophosphate esters as pesticides or nerve agents in chemical warfare caused vital environmental and safety issues. Although metal organic frameworks (MOFs) are often applied to remove the organophosphate esters by adsorption and catalytic degradation, a basic environment with N -ethylmorpholine buffer is essential. In this study, four kinds of zirconium-based MOFs (Zr-MOFs), labeled UiO-66, UiO-67, UiO-67-NH 2 , and UiO-67-2NH 2 , were prepared by the solvothermal method to decontaminate aqueous solutions containing organophosphate esters of paraoxon (POX) and sarin (a nerve agent) without adding any additional basic buffer. Effects of MOF/POX mass ratio and temperature on degradation kinetics and efficiency were investigated in detail. A possible mechanism for the POX decontamination by Zr-MOFs was proposed and verified. Results showed that the POX decontamination catalyzed by Zr-MOFs was a pseudo-first-order reaction. The introduction of amino groups in Zr-MOFs could increase the decontamination rate, which follows the order of "UiO-67-2NH 2 > UiO-67-NH 2 > UiO-67 > UiO-66". The half-lives of POX and sarin with UiO-67-2NH 2 were 18 min and 5 min respectively, and more than 90% POX and 99% sarin could be decontaminated at room temperature. Compared with previous similar studies on POX degradation in N -ethylmorpholine buffer, UiO-67-2NH 2 performs significantly better in terms of catalytic efficiency and environment. This work would broaden the application scope for the decontamination of aqueous solutions containing organophosphate esters under mild conditions, and offer an effective approach for the treatment of chemical warfare agents in modern society. [Display omitted] • Zirconium-based metal organic frameworks (Zr-MOFs) were modified with amino groups. • The introduction of amino groups in Zr-MOFs could improve paraoxon decontamination. • Mechanism of POX degradation catalyzed by Zr-MOFs was proposed and verified. • More than 90% paraoxon can be degraded by Zr-MOFs in neutral aqueous solution. • UiO-67-2NH 2 could remove > 99% of sarin with a t 1/2 of 5 min. [ABSTRACT FROM AUTHOR]

A high-throughput and automated assay for testing the presence of acetylcholine esterase (AChE) inhibiting compounds was developed, validated and applied to screen different types of environmental samples. Automation involved using the assay in 96-well plates and adapting it for the use with an automated workstation. Validation was performed by comparing the results of the automated assay with that of a previously validated and standardised assay for two known AChE inhibitors (paraoxon and dichlorvos). The results show that the assay provides similar concentration-response curves (CRCs) when run according to the manual and automated protocol. Automation of the assay resulted in a reduction in assay run time as well as in intra- and inter-assay variations. High-quality CRCs were obtained for both of the model AChE inhibitors (dichlorvos IC50=120 µM and paraoxon IC50=0.56 µM) when tested alone. The effect of co-exposure of an equipotent binary mixture of the two chemicals were consistent with predictions of additivity and best described by the concentration addition model for combined toxicity. Extracts of different environmental samples (landfill leachate, wastewater treatment plant effluent, and road tunnel construction run-off) were then screened for AChE inhibiting activity using the automated bioassay, with only landfill leachate shown to contain potential AChE inhibitors. Potential uses and limitations of the assay were discussed based on the present results. [ABSTRACT FROM AUTHOR]

Male Siamese fighting fish are highly territorial and aggressive towards conspecifics. We have suggested that aggressive behavior of Betta splendens males is highly sensitive and might be useful as a bioindicator of fresh water pollution. This was tested by determining opercular expansion count and duration when pollutant-exposed fish were confronted by naive fish. We found that paraoxon, a commonly used pesticide used as a model pollutant, inhibits aggressive behavior of Betta males. The results indicate that males treated with paraoxon for 24 hours were significantly less aggressive than control males. The findings suggest that aggressive behavior in Betta splendens may have use as a bioindicator of organophosphate pollution in fresh water. [ABSTRACT FROM AUTHOR]

A combination microwave-assisted hydrothermal and calcination method was used to produce serial mesoporous MgO@Carbon (MgO@C) hybrid nanocomposites, which were studied and validated by TEM, XPS, XRD, and Raman spectra. The calcined MgO@C nanocomposites have a high specific surface area and small grain sizes with an enhanced capacity to degrade paraoxon after optimal preparation. The optimal MgO@C nanocomposites was obtained by the calcining temperature at 600 °C, and the particle size was about 6.4 ± 2 nm with a higher specific surface area of 255.6 m2/g. At room temperature, the decomposed amount of paraoxon toxins by MgO@C-600 is ca. 55.65 mg/g@90 min. Furthermore, the pseudo-second-order kinetic model (R2 > 0.99) fits the experimental degradation data better. The enhanced degradation effect of MgO@C-600 was verified due to the generations of more superoxide radical (·O 2 -) and hydroxyl radical (·OH) active sites. A photothermal effect was also observed in the MgO@C-700 sample. The removal efficiency increased 8-fold after being exposed to near-infrared (NIR) radiation at 808 nm compared to the non-irradiating sample. Because of their ease of manufacture, low cost, and high removal effectiveness, MgO@C nanocomposites could be a suitable adsorbent choice for eliminating organophosphorus hazardous contaminants. [Display omitted] Serial mesoporous MgO@C hybrid nanocomposites with relatively small dimensions and high specific surface areas are generated using a microwave-assisted hydrothermal and calcination process at various calcination temperatures. Such MgO@C nanocomposites show (photothermally) enhanced capacities for eliminating organophosphorus hazardous contaminants. ● Mg(OH) 2 @TEG precursors were obtained via a facile microwave-assisted sol-gel-hydrothermal process. ● Serial mesoporous MgO@C hybrid nanocomposites with featured morphology were obtained under varied calcination temperatures. ● The MgO@C demonstrates (photothermally) enhanced paraoxon toxin removal capability due to the abundant •O 2 - and •OH sites. [ABSTRACT FROM AUTHOR]

Highlights: [•] Reactivation process involves a trigonal bipyramidal structure. [•] The rate-determining step of reactivation process was provided. [•] The H2Oθ-Glu pathway is more feasible for aging process. [•] The electrostatic influences of surrounding amino acids were exhibited. [ABSTRACT FROM AUTHOR]

Highlights: [•] Enzymatically-produced thiocholine modulates the seeded growth of gold nanorods. [•] Acetylcholinesterase activity can be correlated with different nanoparticle shapes. [•] Subnanomolar detection of paraoxon and other nerve gas analogs is achieved. [ABSTRACT FROM AUTHOR]

Abstract: Density functional theory calculations have been used to explore the intrinsic reactivity for the methanolysis of paraoxon (native) and the analogous reactions with sulfur substitutions at key oxygen positions (bridging O2′, O2″, O5′ and nonbridging OP) in the gas phase and in solution. P-path involving the nucleophilic attack at the phosphorus atom and C-path involving the attack at the beta carbon atom are taken into account for the series of reactions. The reactions proceed through the SN2-type mechanism for both of the two pathways. It is found that except for the reaction of sulfur substitution at O5′ position the P-path is more favorable than the C-path kinetically. The products of the C-path are more accessible than the P-path thermodynamically, except for the reaction of sulfur substitution at the leaving (O2′ or O2″) position. The bond-forming is more advanced than the bond-breaking for all of the P-paths, while the bond-breaking is more advanced for all of the C-paths. The calculations provide a comprehensive data set, which are consistent with the previous experimental and theoretical studies and allow interpretation of measured thio effects. [Copyright &y& Elsevier]

The plasmid encoding His-tagged organophosphorus hydrolase (OPH) cloned fromSphingobium fuliginiswas modified to be transferred back to this bacterium. The replication function ofS. amienseplasmid was inserted at downstream of OPH gene, andS. fuliginiswas transformed with this plasmid. The transformant produced larger amount of active OPH with His-tag thanE. coli. [ABSTRACT FROM AUTHOR]

The article provides information on the study of the cell death type and the use of acetylcholinesterase activity in neurotoxicity induced by paraoxon in cultured rat hippocampal neurons. It shows that the neuropathological and morphological modifications induced by paraoxon are both dose and time-dependent. It mentions that dose and vulnerability duration likewise post-exposure time are significant to identify the cholinergic or non-cholinergic effects of paraoxon and type of cell death.

The toxicity of cholinesterase-inhibiting compounds (e.g., carbamates and organophosphates) is due to a decrease in acetylcholine metabolism, which results in a continuous stimulation of cholinergic receptors (muscarinic and nicotinic) that can be fatal. The goal of this study was to evaluate the protective effect of atropine (muscarinic receptor antagonist) against paraoxon-induced toxicity to Daphnia magna using its survival rate for the detection of environmental contamination by cholinesterase-inhibiting compounds. As expected, paraoxon was lethal to D. magna in a concentration-dependent manner. Noteworthy, the pretreatment of these organisms with atropine dramatically increased their survival against paraoxon. These results indicate that muscarinic stimulation plays an important role in paraoxon-induced lethality in D. magna. Therefore, simply by using the survival of atropine-treated and nontreated D. magna, water contamination by cholinesterase-inhibiting compounds may be rapidly and specifically detected. [Copyright &y& Elsevier]

Cerium oxide (CeO 2) prepared by annealing of carbonate precursor was tested for degradation of paraoxon methyl (PO) and the relationships between its properties (specific surface area, crystallite size, number of hydroxyl groups) and the catalytic activity were investigated. Lewis and Brönsted acidity surface sites were identified by adsorption of specific probe molecules (pyridine, acetonitrile, and acetone) using Fourier-transform infrared spectroscopy (FTIR). The abundance of Lewis type sites was recognized while Brönsted type sites were present to a lesser extent. The highest catalytic activity had the sample annealed at 500 °C that was highly crystalline, but the sample retained high surface area and a suitable number of surface hydroxyl groups established to be in the range 0.165–0.190 mmol g−1. Furthermore, the annealing has a negligible effect on the point of zero charge (PZC) but significantly affected the Brunauer-Emmett-Teller surface area (BET), crystallite size and number of surface hydroxyl groups that significantly affected also the degradation efficiency. Nevertheless, it was found that the amount of residual carbonate species on the CeO 2 surface may also have a crucial influence on its catalytic activity. [Display omitted] • CeO 2 catalytic activity was correlated with various surface properties. • Lewis and Brönsted sites were described by FTIR using several probe molecules. • Surface hydroxyl groups have major influence on CeO 2 catalytic activity. • Simple titration method was used for evaluation of acid-base surface properties. • The CeO 2 catalyst was tested for paraoxon methyl degradation. [ABSTRACT FROM AUTHOR]

There is nearly universal exposure to organophosphorus ester insecticides and aromatic amines. Previously we reported that specific aromatic amines and paraoxon induced enhanced mutagenic responses in several S. typhimurium tester strains. In this study we demonstrated that paraoxon could alter the genotoxic potency of mammalian activated m-phenylenediamine (mPDA) and the dietary carcinogens 2-amino-3-methylimidazo-(4,5-f)quinoline (IQ) and 2-amino-l-methyl-6-phenylimidazo(4,5-b)pyridine (PhIP) as measured in S. typhimurium and in human lymphocytes. Paraoxon alone was not genotoxic in any of the assays. All threearomatic amines exhibited paraoxon-mediated mutagenic synergy when assayed with S. typhimurium strain YG1024. However, using the single cell gel electrophoresis (Comet) assay with lymphocytes, a paraoxon concentration-dependent genotoxic synergy was induced with mPDA. A bimodal response was observed with lymphocytes treated with a constant amount of IQ or PhIP and with 1 to 500 Mu M paraoxon. At low paraoxon concentrations a significant increase in the comet tail moment value was induced when compared with the cells treated with IQ or PhIP alone. At higher paraoxon concentrations a significant antigenotoxic response was observed. These data demonstrate that an environmental agent such as paraoxon, can induce both genotoxic synergy and antigenotoxicity in human cells depending on its concentration. This result raisesthe concern of the environmental effects of organophosphorus ester insecticides under realworld conditions where people are exposed to a multitude of genotoxic agents. [ABSTRACT FROM AUTHOR]