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Synthesis of the acetylcholinesterase inhibitor paraoxon (POX) as a carbon-11 positron emission tomography tracer ([11C]POX) and profiling in live rats is reported. Naïve rats intravenously injected with [11C]POX showed a rapid decrease in parent tracer to ∼1%, with an increase in radiolabeled serum proteins to 87% and red blood cells (RBCs) to 9%. Protein and RBC leveled over 60 minutes, reflecting covalent modification of proteins by [11C]POX. Ex vivo biodistribution and imaging profiles in naïve rats had the highest radioactivity levels in lung followed by heart and kidney, and brain and liver the lowest. Brain radioactivity levels were low but observed immediately after injection and persisted over the 60-minute experiment. This showed for the first time that even low POX exposures (∼200 ng tracer) can rapidly enter brain. Rats given an LD50 dose of nonradioactive paraoxon at the LD50 20 or 60 minutes prior to [11C]POX tracer revealed that protein pools were blocked. Blood radioactivity at 20 minutes was markedly lower than naïve levels due to rapid protein modification by nonradioactive POX; however, by 60 minutes the blood radioactivity returned to near naïve levels. Live rat tissue imaging-derived radioactivity values were 10%-37% of naïve levels in nonradioactive POX pretreated rats at 20 minutes, but by 60 minutes the area under the curve (AUC) values had recovered to 25%-80% of naïve. The live rat imaging supported blockade by nonradioactive POX pretreatment at 20 minutes and recovery of proteins by 60 minutes. SIGNIFICANCE STATEMENT: Paraoxon (POX) is an organophosphorus (OP) compound and a powerful prototype and substitute for OP chemical warfare agents (CWAs) such as sarin, VX, etc. To study the distribution and penetration of POX into the central nervous system (CNS) and other tissues, a positron emission tomography (PET) tracer analog, carbon-11-labeled paraoxon ([11C]POX), was prepared. Blood and tissue radioactivity levels in live rats demonstrated immediate penetration into the CNS and persistent radioactivity levels in tissues indicative of covalent target modification.

We have shown that briefly inhaled isoflurane rapidly halts convulsions and protects the central nervous system (CNS) from organophosphate-induced neuronal loss when administered at 5% for 5 min, even as late as 1 h after organophosphate exposure. In the current study we investigated if an injectable form of isoflurane was as effective as inhaled isoflurane. We used a mixture of 10% isoflurane dissolved in an IV-compatible lipid-water emulsion for intravenous administration. Rats with an implanted jugular vein cannula were infused with 1,000 µL of the 10% isoflurane-lipid emulsion (ILE) mixture at a rate of 200 µL per minute, which achieved full anesthesia lasting approximately 10 min. When administered 30 min after a highly lethal dose of the organophosphate insecticide paraoxon (POX), the short-duration administration halted convulsions over the course of the study and prevented the great majority of neuronal loss as shown by Fluoro-Jade B staining (FJB). Our results indicate that injectable isoflurane is very effective for treating organophosphate poisoning, negating the need for vaporizer equipment and enabling intravenous therapy. [ABSTRACT FROM AUTHOR]

The atomically precise gold nanoclusters (AuNCs) and MnO2 nanosheets (MnO2 NSs) were synthesized and characterized as donor and acceptor pairs, respectively. A Förster resonance energy transfer (FRET)-based highly sensitive "turn on–off" fluorescence (FL) response was achieved owing to the strong spectral overlapping between highly bright luminescence of as-synthesized vitamin B1-stabilized gold nanoclusters (VB1–AuNCs) and absorption spectra of manganese oxide nanosheet (MnO2 NS)-based 2D material. The AuNC–MnO2 NSs pair was used as a probe for the assessment of enzymatic activity of acetylcholinesterase (AChE) as an effective alternative to Ellman's reagent. Our work predicts that an abundantly hydrophilic nano gold cluster surface would be a promising material to improve the sensitivity and hydrolytic rate (kcat) of AChE enzymes. The reconciliation and inhibition of AChE for the hydrolysis of acetylthiocholine furnish quantitative turn "on–off" FL signals in the linear range of 0.53–1.6 × 10–8 M of paraoxon. The excellence of this sensor is demonstrated by its exceptionally low limit of detection (LOD) of 1.6 nM and limit of quantification (LOQ) of 4.9 nM values for detection of paraoxon. The applicability of the proposed sensing system was verified using environmental (farm water) and fruit matrixes like tomato, grapes, and apple samples. [ABSTRACT FROM AUTHOR]

CeO2 nanoparticles possess catalytic activity for hydrolysis of organophosphates such as paraoxon and nerve agents used in chemical warfare. Intoxication with these highly toxic compounds can occur directly through inhalation or dermal contact and lead to rapid and severe consequences including death. It is therefore necessary to have effective means of skin decontamination, and CeO2 nanoparticles are promising. In this study, a wide range of CeO2 nanoparticles were synthesized and their efficiency against paraoxon degradation was evaluated. Nanocubes (NC), nanorods (NR), nano-octahedra (NO), and nanopolyhedra (NPO) were studied along with nanoparticles obtained after calcination (NC*, NR*, NO*, and nanotruncated octahedra NTO*). Results show an influence of calcination, specific surface area, and crystal facets with higher activity for {111} facets compared to {100} facets. pH also impacted POX degradation rates, with higher pH accelerating the degradation. In vitro tests using the Franz cell method demonstrated the skin decontamination efficacy of the CeO2 nanoparticles. NC* exhibited lower efficiency, possibly due to smaller surface area and limited {100} facet degradation. The most efficient nanoparticles were NR* and NO* followed by NTO* consistently with their degradation efficiency and specific surface area. Notably, NR* and NO* performed comparably to FE (Fuller's earth), the standard powder skin decontaminant on battlefield. Unlike FE that can only adsorb paraoxon, CeO2 nanoparticles can neutralize it into safer byproducts. This study highlights the interest of CeO2 nanoparticles and the influence of their physicochemical properties on organophosphorus compound degradation and cutaneous decontamination. [ABSTRACT FROM AUTHOR]

Nerve agents, including organophosphorus compounds such as paraoxon, are potent and highly toxic chemicals with grave implications for human health and the environment. In this paper, we present the development of a novel enzyme inhibition-based biosensor for the sensitive and selective detection of paraoxon, which is commonly used as a surrogate for nerve agents. The biosensor employs reduced graphene oxide as a screen-printed electrode surface modification nanomaterial, leading to increased surface electroactivity and, thus, more sensitive detection. The biosensor exhibits a low detection limit of 0.56 pg/ml (limit of detection, LOD) and 1.25 pg/ml (limit of quantification, LOQ), highlighting its high sensitivity for trace-level analysis of nerve agents in complex sample matrices. Our biosensor demonstrates remarkable selectivity for paraoxon, with minimal interference from other non-target chemicals. Stability and repeatability tests reveal that the system maintains its performance integrity over a 45-day period and consistently produces readings with a margin of error of only 5%. Real sample testing in river water, wastewater, and tap water further confirms the biosensor's practical utility, with recovery percentages ranging from 84 to 115%. This biosensor represents a significant advancement in biosensor technology, facilitating the rapid, cost-effective, and reliable detection of toxic substances in real-world scenarios. [ABSTRACT FROM AUTHOR]

Intentional and unintentional organophosphorus pesticide exposure is a public health concern. Organothiophosphate compounds require metabolic bioactivation by the cytochrome P450 system to their corresponding oxon analogues to act as potent inhibitors of acetylcholinesterase. It is known that interactions between cytochrome P450 and pesticides include the inhibition of major xenobiotic metabolizing cytochrome P450 enzymes and changes on the genetic level. In this in vitro study, the influence of the pesticides parathion and paraoxon on human cytochrome P450 and associated oxygenases was investigated with a metabolically competent cell line (HepaRG cells). First, the viability of the cells after exposure to parathion and paraoxon was evaluated. The inhibitory effect of both pesticides on cytochrome P450 3A4, which is a pivotal enzyme in the metabolism of xenobiotics, was examined by determining the dose-response curve. Changes on the transcription level of 92 oxygenase associated genes, including those for important cytochrome P450 enzymes, were evaluated. The exposure of HepaRG cells to parathion and paraoxon at concentrations up to 100 µM resulted in a viability of 100 per cent. After exposure for 24 hours, pronounced inhibition of cytochrome P450 3A4 enzyme activity was shown, indicating 50 per cent effective concentrations of 1.2 µM (parathion) and 2.1 µM (paraoxon). The results revealed that cytochrome P450 involved in parathion metabolism were significantly upregulated. Relevant changes of the cytochrome P450 3A4 enzyme activity and significant alteration of genes associated with cytochrome P450 suggest an interference of pesticide exposure with numerous metabolic processes. The major limitations of the work involve the use of a single pesticide and the in vitro model as surrogate to human hepatocytes. The data of this study might be of relevance after survival of acute, life-threatening intoxications with organophosphorus compounds, particularly for the co-administration of drugs, which are metabolized by the affected cytochrome P450. [ABSTRACT FROM AUTHOR]

We have shown that briefly inhaled isoflurane rapidly halts convulsions and protects the central nervous system (CNS) from organophosphate-induced neuronal loss when administered at 5% for 5 min, even as late as 1 h after organophosphate exposure. In the current study we investigated if an injectable form of isoflurane was as effective as inhaled isoflurane. We used a mixture of 10% isoflurane dissolved in an IV-compatible lipid-water emulsion for intravenous administration. Rats with an implanted jugular vein cannula were infused with 1,000 μL of the 10% isoflurane-lipid emulsion (ILE) mixture at a rate of 200 μL per minute, which achieved full anesthesia lasting approximately 10 min. When administered 30 min after a highly lethal dose of the organophosphate insecticide paraoxon (POX), the short-duration administration halted convulsions over the course of the study and prevented the great majority of neuronal loss as shown by Fluoro-Jade B staining (FJB). Our results indicate that injectable isoflurane is very effective for treating organophosphate poisoning, negating the need for vaporizer equipment and enabling intravenous therapy.

The hydrolytic decomposition of the organophosphorus ecotoxicant paraoxon in alkaline micellar solutions of a cationic surfactant with a carbamate fragment (CB-2-16) has been investigated by means of spectrophotometry. The stronger catalytic effect of micellar solutions aged during several days in comparison with freshly prepared ones has been associated with alkaline hydrolysis of the carbamate surfactant and the formation of a mixed system of CB-2-16 with its decomposition product cetyl(2-hydroxyethyl)dimethylammonium bromide (1H NMR spectroscopy data). In the absence of alkali, the decomposition products of the carbamate surfactant have not been detected for more than four months, indicating its hydrolytic stability in a neutral environment. [ABSTRACT FROM AUTHOR]

Kathleen F Pirollo,1 Manish Moghe,1 Miaoyin Guan,1 Antonina S Rait,1 Aibing Wang,1 Sang-Soo Kim,1,2 Esther H Chang,1 Joe B Harford2 1Department of Oncology, Lombardi Comprehensive Cancer Center, Georgetown University Medical Center, Washington, DC, 20057, USA; 2SynerGene Therapeutics, Inc., Potomac, MD, 20854, USACorrespondence: Esther H Chang, Lombardi Comprehensive Cancer Center, Georgetown University, 3970 Reservoir Road N.W., Research Building E420, Washington, DC, 20057, USA, Tel +1 202 687 8418, Email change@georgetown.eduIntroduction: Organophosphates are among the deadliest of known chemicals based on their ability to inactivate acetylcholinesterase in neuromuscular junctions and synapses of the central and peripheral nervous systems. The consequent accumulation of acetylcholine can produce severe acute toxicities and death. Oxime antidotes act by reactivating acetylcholinesterase with the only such reactivator approved for use in the United States being 2-pyridine aldoxime methyl chloride (a.k.a., pralidoxime or 2-PAM). However, this compound does not cross the blood–brain barrier readily and so is limited in its ability to reactivate acetylcholinesterase in the brain.Methods: We have developed a novel formulation of 2-PAM by encapsulating it within a nanocomplex designed to cross the blood–brain barrier via transferrin receptor-mediated transcytosis. This nanocomplex (termed scL-2PAM) has been subjected to head-to-head comparisons with unencapsulated 2-PAM in mice exposed to paraoxon, an organophosphate with anticholinesterase activity.Results and Discussion: In mice exposed to a sublethal dose of paraoxon, scL-2PAM reduced the extent and duration of cholinergic symptoms more effectively than did unencapsulated 2-PAM. The scL-2PAM formulation was also more effective than unencapsulated 2-PAM in rescuing mice from death after exposure to otherwise-lethal levels of paraoxon. Improved survival rates in paraoxon-exposed mice were accompanied by a higher degree of reactivation of brain acetylcholinesterase.Conclusion: Our data indicate that scL-2PAM is superior to the currently used form of 2-PAM in terms of both mitigating paraoxon toxicity in mice and reactivating acetylcholinesterase in their brains.Keywords: lipid nanoparticle, nanodelivery, organophosphate, paraoxon, blood–brain barrier, transcytosis

Organophosphate-based chemical agents (OP), including nerve agents and certain pesticides such as paraoxon, are potent acetylcholinesterase inhibitors that cause severe convulsions and seizures, leading to permanent central nervous system (CNS) damage if not treated promptly. The current treatment regimen for OP poisoning is intramuscular injection of atropine sulfate with an oxime such as pralidoxime (2-PAM) to mitigate cholinergic over-activation of the somatic musculature and autonomic nervous system. This treatment does not provide protection against CNS cholinergic overactivation and therefore convulsions require additional medication. Benzodiazepines are the currently accepted treatment for OP-induced convulsions, but the convulsions become refractory to these GABAA agonists and repeated dosing has diminishing effectiveness. As such, adjunct anticonvulsant treatments are needed to provide improved protection against recurrent and prolonged convulsions and the associated excitotoxic CNS damage that results from them. Previously we have shown that brief, 4-min administration of 3%–5% isoflurane in 100% oxygen has profound anticonvulsant and CNS protective effects when administered 30 min after a lethal dose of paraoxon. In this report we provide an extended time course of the effectiveness of 5% isoflurane delivered for 5 min, ranging from 60 to 180 min after a lethal dose of paraoxon in rats. We observed substantial effectiveness in preventing neuronal loss as shown by Fluoro-Jade B staining when isoflurane was administered 1 h after paraoxon, with diminishing effectiveness at 90, 120 and 180 min. In vivo magnetic resonance imaging (MRI) derived T2 and mean diffusivity (MD) values showed that 5-min isoflurane administration at a concentration of 5% prevents brain edema and tissue damage when administered 1 h after a lethal dose of paraoxon. We also observed reduced astrogliosis as shown by GFAP immunohistochemistry. Studies with continuous EEG monitoring are ongoing to demonstrate effectiveness in animal models of soman poisoning. [ABSTRACT FROM AUTHOR]

Organophosphate-based chemical agents (OP), including nerve agents and certain pesticides such as paraoxon, are potent acetylcholinesterase inhibitors that cause severe convulsions and seizures, leading to permanent central nervous system (CNS) damage if not treated promptly. The current treatment regimen for OP poisoning is intramuscular injection of atropine sulfate with an oxime such as pralidoxime (2-PAM) to mitigate cholinergic over-activation of the somatic musculature and autonomic nervous system. This treatment does not provide protection against CNS cholinergic overactivation and therefore convulsions require additional medication. Benzodiazepines are the currently accepted treatment for OP-induced convulsions, but the convulsions become refractory to these GABAA agonists and repeated dosing has diminishing effectiveness. As such, adjunct anticonvulsant treatments are needed to provide improved protection against recurrent and prolonged convulsions and the associated excitotoxic CNS damage that results from them. Previously we have shown that brief, 4-min administration of 3%-5% isoflurane in 100% oxygen has profound anticonvulsant and CNS protective effects when administered 30 min after a lethal dose of paraoxon. In this report we provide an extended time course of the effectiveness of 5% isoflurane delivered for 5 min, ranging from 60 to 180 min after a lethal dose of paraoxon in rats. We observed substantial effectiveness in preventing neuronal loss as shown by Fluoro-Jade B staining when isoflurane was administered 1 h after paraoxon, with diminishing effectiveness at 90, 120 and 180 min. In vivo magnetic resonance imaging (MRI) derived T2 and mean diffusivity (MD) values showed that 5-min isoflurane administration at a concentration of 5% prevents brain edema and tissue damage when administered 1 h after a lethal dose of paraoxon. We also observed reduced astrogliosis as shown by GFAP immunohistochemistry. Studies with continuous EEG monitoring are ongoing to demonstrate effectiveness in animal models of soman poisoning. [ABSTRACT FROM AUTHOR]

Organophosphorus compounds (OPs) are phosphoric acid derivatives represented by the formula (R2XP=O/S), R as organic groups; however, they need not contain a direct carbonphosphorus bond. The organophosphorus compounds can be categorized into three classes, viz., organophosphates, carbamates nerve agents. The OPs having application as insecticides are generally phosphorothioates (i.e., containing P=S bond). These sulfur analogs are first bioactivated (in vivo) and converted to oxygen analogs responsible for exerting toxic action. These organophosphorus compounds are esters, fluorides, anhydrides, and amides of phosphoric, phosphorothioate, and phosphorodithioic acids. The toxicity of OPs is related to their molecular structure, metabolism in the targeted organisms, concentration, mode of decomposition, application, ingestion in organisms, etc. Exposure to OPs leads to the appearance of neurological symptoms followed by acute poisoning by targeting the target primarily, acetylcholine (AChE). However, secondary targets and other harmful effects besides nerve system problems are also reported. Organophosphates poison insects and other animals, including birds, amphibians, and mammals. These chemicals can have neural effects (Neurotoxicity), non-neuronal effects, or acute toxicity, which may also result in fatality. Their uncontrollable widespread became a significant threat to the environment; thus, corrective measures have been essential to save living beings and the environment from further damage. [ABSTRACT FROM AUTHOR]

Acetylcholinesterase (EC 3.1.1.7), a key acetylcholine-hydrolyzing enzyme in cholinergic neurotransmission, is present in a variety of states in situ, including monomers, C-terminally disulfide-linked homodimers, homotetramers, and up to three tetramers covalently attached to structural subunits. Could oligomerization that ensures high local concentrations of catalytic sites necessary for efficient neurotransmission be affected by environmental factors? Using small-angle X-ray scattering (SAXS) and cryo-EM, we demonstrate that homodimerization of recombinant monomeric human acetylcholinesterase (hAChE) in solution occurs through a C-terminal four-helix bundle at micromolar concentrations. We show that diethylphosphorylation of the active serine in the catalytic gorge or isopropylmethylphosphonylation by the RP enantiomer of sarin promotes a 10-fold increase in homodimer dissociation. We also demonstrate the dissociation of organophosphate (OP)-conjugated dimers is reversed by structurally diverse oximes 2PAM, HI6, or RS194B, as demonstrated by SAXS of diethylphosphoryl-hAChE. However, binding of oximes to the native ligand-free hAChE, binding of high-affinity reversible ligands, or formation of an SP-sarin-hAChE conjugate had no effect on homodimerization. Dissociation monitored by time-resolved SAXS occurs in milliseconds, consistent with rates of hAChE covalent inhibition. OP-induced dissociation was not observed in the SAXS profiles of the double-mutant Y337A/F338A, where the active center gorge volume is larger than in wildtype hAChE. These observations suggest a key role of the tightly packed acyl pocket in allosterically triggered OP-induced dimer dissociation, with the potential for local reduction of acetylcholine-hydrolytic power in situ. Computational models predict allosteric correlated motions extending from the acyl pocket toward the four-helix bundle dimerization interface 25 Å away.

Organophosphate-based chemical agents (OP), including nerve agents and certain pesticides such as paraoxon, are potent acetylcholinesterase inhibitors that cause severe convulsions and seizures, leading to permanent central nervous system (CNS) damage if not treated promptly. The current treatment regimen for OP poisoning is intramuscular injection of atropine sulfate with an oxime such as pralidoxime (2-PAM) to mitigate cholinergic over-activation of the somatic musculature and autonomic nervous system. This treatment does not provide protection against CNS cholinergic overactivation and therefore convulsions require additional medication. Benzodiazepines are the currently accepted treatment for OP-induced convulsions, but the convulsions become refractory to these GABAA agonists and repeated dosing has diminishing effectiveness. As such, adjunct anticonvulsant treatments are needed to provide improved protection against recurrent and prolonged convulsions and the associated excitotoxic CNS damage that results from them. Previously we have shown that brief, 4-min administration of 3%–5% isoflurane in 100% oxygen has profound anticonvulsant and CNS protective effects when administered 30 min after a lethal dose of paraoxon. In this report we provide an extended time course of the effectiveness of 5% isoflurane delivered for 5 min, ranging from 60 to 180 min after a lethal dose of paraoxon in rats. We observed substantial effectiveness in preventing neuronal loss as shown by Fluoro-Jade B staining when isoflurane was administered 1 h after paraoxon, with diminishing effectiveness at 90, 120 and 180 min. In vivo magnetic resonance imaging (MRI) derived T2 and mean diffusivity (MD) values showed that 5-min isoflurane administration at a concentration of 5% prevents brain edema and tissue damage when administered 1 h after a lethal dose of paraoxon. We also observed reduced astrogliosis as shown by GFAP immunohistochemistry. Studies with continuous EEG monitoring are ongoing to demonstrate effectiveness in animal models of soman poisoning.

Organophosphorus insecticides (OPs), acting as serine phosphorylating agents in acetylcholinesterase (AChE), are highly effective neurotoxic insecticides. In our previous research, we found that six herbivorous pests and four ladybirds howed significantly higher AChE LC50 values than seven parasitoids and a predator (Epistrophe balteate), and that there was a significant correlation with the corresponding bimolecular rate constant (Ki) value. The Ki value of pests was much smaller than that of natural enemies and had a higher LC50 value.Then, we speculated that the low sensitivity of the pest AChE to OPs may be associated with its higher recovery and lower aging ability. In this work, the I50 and I90 were calculated, to determine the sensibility of AChE in ten representative species, including Plutella xylostella, Prodenia litura, Musca domestica, and Cavia porcellus, to paraoxon and malaoxon. The enzyme activities were measured at various time points, and kinetic calculations were used to obtain their spontaneous reactivation (Ks) and aging (Ka) constants, which were comprehensively compared. We conclude that the Ka and Ks of the AChE inhibited by OPs showed primarily species-specific correlations, and little correlation with the sensitivity to OPs. The differences in the AChE sensitivity to paraoxon among the ten species were much greater than in the sensitivity to malaoxon. Compared to paraoxon, malaoxon was more selective for Cavia porcellus. Coleoptera insects showed a stronger dephosphorylation ability than other insect groups. The recovery ability of phospho-AChE was stronger in mammals than in insects, which could be related to the low sensitivity of the AChE site of action to OPs. The Ka of the AChE inhibited by malaoxon was larger than that inhibited by paraoxon with the corresponding biomaterials, indicating that the OP type had a substantial relationship with the Ka of the AChE. We further discovered that, when insects were inhibited by OP, the tendency of AChE to undergo aging was greater than that of dephosphorylation. Overall, the study provides valuable information on the action mechanism of various OPs on AChE in several species, which could be used to further research into AChE and the potential dangers that organophosphates pose to animals. [ABSTRACT FROM AUTHOR]

The ongoing advancement in the synthesis of new nanomaterials has accelerated the rapid development of non-enzymatic pesticide sensors based on electrochemical platforms. This study aims to develop and characterize Nano-ink for applying organophosphorus pesticides using paraoxon residue detection. Multi-walled carbon nanotubes, silicon carbide, and silver nanoparticles were used to create Nano-ink using a green synthesis process in 1:1:0, 1:1:0.5, and 1:1:1 ratios, respectively. These composites were combined with chitosan of varying molecular weights, which served as a stabilizing glue to keep the Nano-ink employed in a functioning electrode stable. By using X-ray powder diffraction, Raman spectroscopy, energy dispersive X-ray spectroscopy, and a field emission scanning electron microscope, researchers were able to examine the crystallinity, element composition, and surface morphology of Nano-ink. The performance of the proposed imprinted working electrode Nano-ink was investigated using cyclic voltammetry and differential pulse voltammetry techniques. The Cyclic voltammogram of Ag NPs/chitosan (medium, 50 mg) illustrated high current responses and favorable conditions of the Nano-ink modified electrode. Under the optimized conditions, the reduction currents of paraoxon using the DPV techniques demonstrated a linear reaction ranging between 0.001 and 1.0 µg/mL (R2 = 0.9959) with a limit of detection of 0.0038 µg/mL and a limit of quantitation of 0.011 µg/mL. It was concluded that the fabricated Nano-ink showed good electrochemical activity for non-enzymatic paraoxon sensing. [ABSTRACT FROM AUTHOR]

In the current work, a novel ZnO-Cu2O heterojunction was synthesized from ZnO nanorods and Cu2O nanoparticles via hydrothermal route and was applied for the first time as a visible light active photocatalyst for decomposition of Paraoxon insecticide. Crystallinity, shape and size of particles, and optical properties of the synthesized heterojunction nanocomposites were evaluated by XRD, FESEM, EDS, Mott-Schottky, photocurrent analysis and UV-Visible spectroscopy analyses. Based on the obtained results the ZnO-Cu2O heterojunction nanocomposite was successfully synthesized and compared to pure ZnO semiconductor has the enhanced photocatalytic efficiency. The nanocomposite with 40% weight percentage of Cu2O has the best photocatalytical activity of 0.0201 min-1, which could be related to the improvement of optical properties (increasing of the visible light harvesting ability) and the reduction of the recombination of the photoinduced electron-hole pairs. In addition, according to the radical trapping tests and Mott-Schottky experiments, superoxide radical was determined as the main oxidizing species for photocatalytic degradation of Paraoxon, and a type II charge transfer process was proposed for the improved photocatalytic activity.

Organophosphorus hydrolase (OPH) is a metalloenzyme that can hydrolyze organophosphorus agents resulting in products that are generally of reduced toxicity. The best OPH substrate found to date is diethyl p-nitrophenyl phosphate (paraoxon). Most structural and kinetic studies assume that the binding orientation of paraoxon is identical to that of diethyl 4-methylbenzylphosphonate, which is the only substrate analog co-crystallized with OPH. In the current work, we used a combined docking and molecular dynamics (MD) approach to predict the likely binding mode of paraoxon. Then, we used the predicted binding mode to run MD simulations on the wild type (WT) OPH complexed with paraoxon, and OPH mutants complexed with paraoxon. Additionally, we identified three hot-spot residues (D253, H254, and I255) involved in the stability of the OPH active site. We then experimentally assayed single and double mutants involving these residues for paraoxon binding affinity. The binding free energy calculations and the experimental kinetics of the reactions between each OPH mutant and paraoxon show that mutated forms D253E, D253E-H254R, and D253E-I255G exhibit enhanced substrate binding affinity over WT OPH. Interestingly, our experimental results show that the substrate binding affinity of the double mutant D253E-H254R increased by 19-fold compared to WT OPH.

Oxime antidotes regenerate organophosphate-inhibited acetylcholinesterase (AChE). Although they share a common mechanism of AChE reactivation, the rate and amount of oxime that enters the brain are critical to the efficacy, a process linked to the oxime structure and charge. Using a platform based on the organophosphate [18 F]-VXS as a positron emission tomography tracer for active AChE, the in vivo distribution of [18 F]-VXS was evaluated after an LD50 dose (250 μg/kg) of the organophosphate paraoxon (POX) and following oximes as antidotes. Rats given [18 F]-VXS tracer alone had significantly higher radioactivity (two- to threefold) in the heart and lung than rats given LD50 POX at 20 or 60 min prior to [18 F]-VXS. When rats were given LD50 POX followed by 2-PAM (cationic), RS194b (ionizable), or monoisonitrosoacetone (MINA) (neutral), central nervous system (CNS) radioactivity returned to levels at or above untreated naive rats (no POX), whereas CNS radioactivity did not increase in rats given the dication oximes HI-6 or MMB-4. MINA showed a significant, pairwise increase in CNS brain radioactivity compared with POX-treated rats. This new in vivo dynamic platform using [18 F]-VXS tracer measures and quantifies peripheral and CNS relative changes in AChE availability after POX exposure and is suitable for comparing oxime delivery and AChE reactivation in rats.

Aptamer-modified Zr-MOFs (UiO-66-APT) were constructed as nanocatalysts for achieving specific hydrolysis of paraoxon. The conjunction mode of the aptamer on the Zr-MOFs affected the binding of the substrates with the catalytic sites, thus leading to different catalytic activities. This study provides a solution for achieving specific catalysis of nanocatalysts, just like that in natural enzymes. [ABSTRACT FROM AUTHOR]

A liquid crystal-based assay (LC) was developed to monitor paraoxon by incorporating a Cu2+ -coated substrate and the inhibitory effect of paraoxon with acetylcholinesterase (AChE). We observed that thiocholine (TCh), a hydrolysate of AChE and acetylthiocholine (ATCh), interfered with the alignment of 5CB films through a reaction between Cu2+ ions and the thiol moiety of TCh. The catalytic activity of AChE was inhibited in the presence of paraoxon due to the irreversible interaction between TCh and paraoxon; consequently, no TCh molecule was available to interact with Cu2+ on the surface. This resulted in a homeotropic alignment of the liquid crystal. The proposed sensor platform sensitively quantified paraoxon with a detection limit of 2.20 ± 0.11 (n = 3) nM within a range of 6 to 500 nM. The specificity and reliability of the assay were verified by measuring paraoxon in the presence of various suspected interfering substances and spiked samples. As a result, the sensor based on LC can potentially be used as a screening tool for accurate evaluation of paraoxon and other organophosphorus compounds. [ABSTRACT FROM AUTHOR]

In this study, a novel conductive polymer comprising biosensor based on poly‐2,2′‐(9,9‐dioctyl‐9 h‐fluorene‐2,7‐diyl)bistiophene (Poly(BT)) and acetylcholinesterase (AChE) was reported for the determination of paraoxon. This practical biosensor allowed to catalyze electrochemical oxidation of acetylthiocholine (+0.6 V vs. Ag reference). The detection range for acetylcholine chloride (AThCl) with Poly(BT)/AChE was found to be 0.025–4 mM. In pesticide analysis, wide linear ranges from 0.5 to 1 μg/L and 1 to 14 μg/L, and a low detection limit of 0.033 μg/L were estimated. Under optimum operating conditions, the developed biosensor was used for pesticide detection in milk and tap water samples, effectively. [ABSTRACT FROM AUTHOR]

Exposure to paraoxon (POX) and leptin (LP) could cause an imbalance between oxidants and antioxidants in an organism, which can be prevented by introduction of exogenous antioxidants such as N-acetylcysteine (NAC). The aim of this study was to evaluate synergic or additive effects of administration of exogenous LP plus POX on the antioxidant status, as well as the prophylactic and therapeutic roles of NAC in various rat tissues. Fifty-four male Wistar rats were divided into nine groups treated with different compounds: Control (no treatment), POX (0.7 mg/kg), NAC (160 mg/kg), LP (1 mg/kg), POX+LP, NAC-POX, POX-NAC, NAC-POX+LP, and POX+LP-NAC. In the last five groups, only the order of administered compounds differed. After 24 h, plasma and tissues were sampled and examined. The results showed that administration of POX plus LP significantly increased biochemical indices in plasma and antioxidant enzymes activities and decreased glutathione content in the liver, erythrocytes, brain, kidney, and heart. In addition, cholinesterase and paraoxonase 1 activities in the POX+LP-treated group were decreased and malondialdehyde level was increased in the liver, erythrocytes, and brain. However, administration of NAC rectified induced changes although not to the same extent. Our study suggests that POX or LP administration engage the oxidative stress system per se; however, their combination did not produce significantly greater effects. Moreover, both prophylactic and therapeutic treatments of rats with NAC supported the antioxidant defense against oxidative damage in tissues, most probably through both its free radical scavenging ability and maintaining intracellular GSH levels. It can therefore be suggested that NAC has particularly protective effects against POX or/and LP toxicity. [ABSTRACT FROM AUTHOR]

Background and purpose: Exposure to organophosphorus (OP) compounds may contribute to an increased risk of cognitive impairments and induction of oxidative stress. The present study was designed to evaluate the effects of exposure to paraoxon (the active metabolite of insecticide parathion) on cognitive function and oxidative stress biomarkers. Materials and methods: Adult male Wistar rats (n= 56, 7 per group) were used in this study. Corn oil or paraoxon at 0.3, 0.7, or 1 mg/kg were intraperitoneally administrated. After 14 or 28 days, the animals were examined by Morris water maze to determine spatial learning and memory. The effects of paraoxon on hippocampal glutathione (GSH) and malondialdehyde (MDA) levels were also investigated. Results: Escape latency and swimming distance significantly increased in animals that received 1 mg/kg of paraoxon at both time points (P0.05). Exposure to paraoxon 1 mg/kg was associated with decreased GSH and increased MDA levels in the hippocampus. Conclusion: The study showed that exposure to high dose of paraoxon (1 mg/kg) impaired spatial learning and memory independent of any changes in sensorimotor deficit. Induction of oxidative stress plays an important role in development of cognitive impairments caused by exposure to paraoxon.

Acute toxicity of organophosphorus compounds is primarily caused by inhibition of acetylcholinesterase (AChE) at cholinergic synapses. The current study was designed to investigate the effects of paraoxon on histological changes as well as the role of mitochondrion-dependent apoptosis in causing this damage in the rat cerebellum. Adult male Wistar rats were intraperitoneally injected with paraoxon at 0.3, 0.7, or 1 mg/kg. Control animals were injected with corn oil as a vehicle. At 14 or 28 days after intoxication, histological changes and alterations in the expression of apoptosis-related proteins, including Bax, Bcl-2, and caspase-3, were investigated in the cerebellum using cresyl violet staining and western blotting, respectively. Findings showed the decreased thickness of both molecular and granular layers and reduction in the number of Purkinje cells in animals treated with a higher convulsive dose of paraoxon (1 mg/kg). In addition, exposure of rats to 1 mg/kg of paraoxon activated apoptosis pathway confirmed by an increase in Bax and caspase-3 and a decrease in Bcl-2 protein levels. According to our results, cerebellar histological changes and alterations in the expression of apoptosis-related proteins occur following exposure to a high convulsive dose of paraoxon and persist for a long time. [ABSTRACT FROM AUTHOR]

The ongoing advancement in the synthesis of new nanomaterials has accelerated the rapid development of non-enzymatic pesticide sensors based on electrochemical platforms. This study aims to develop and characterize Nano-ink for applying organophosphorus pesticides using paraoxon residue detection. Multi-walled carbon nanotubes, silicon carbide, and silver nanoparticles were used to create Nano-ink using a green synthesis process in 1:1:0, 1:1:0.5, and 1:1:1 ratios, respectively. These composites were combined with chitosan of varying molecular weights, which served as a stabilizing glue to keep the Nano-ink employed in a functioning electrode stable. By using X-ray powder diffraction, Raman spectroscopy, energy dispersive X-ray spectroscopy, and a field emission scanning electron microscope, researchers were able to examine the crystallinity, element composition, and surface morphology of Nano-ink. The performance of the proposed imprinted working electrode Nano-ink was investigated using cyclic voltammetry and differential pulse voltammetry techniques. The Cyclic voltammogram of Ag NPs/chitosan (medium, 50 mg) illustrated high current responses and favorable conditions of the Nano-ink modified electrode. Under the optimized conditions, the reduction currents of paraoxon using the DPV techniques demonstrated a linear reaction ranging between 0.001 and 1.0 µg/mL (R2 = 0.9959) with a limit of detection of 0.0038 µg/mL and a limit of quantitation of 0.011 µg/mL. It was concluded that the fabricated Nano-ink showed good electrochemical activity for non-enzymatic paraoxon sensing.

Fatalities from organophosphate (OP) insecticide result from both occupational and deliberate exposure; significantly impacting human health. Like nerve agents, insecticides are neurotoxins which target and inhibit acetylcholinesterases (AChE) in central and peripheral synapses in the cholinergic nervous system. Post-exposure therapeutic countermeasures generally include administration of atropine with a pyridinium aldoxime e.g. pralidoxime, to reactivate the OP-inhibited AChE. However, commonly used oximes inefficiently cross the bloodbrain barrier and are rapidly cleared and their benefit is debated. Recent findings have demonstrated the ability of a novel zwitterionic, centrally acting, brain penetrating oxime (RS194B) to reverse severe symptoms and rapidly reactivate sarin-inhibited AChE in macaques, but it has not been tested following OP pesticide poisoning. In the present study, the symptoms following a lethal dose of inhaled paraoxon (100ug/kg), were shown to mimic those in insecticide poisoned individuals and were also rapidly reversed in macaques by post-exposure IM administration of 80mg/kg of RS194B. This occurred with a concomitant reactivation of AChE to 40-100% in

Paraoxon is an emerging organophosphate pollutant that is commonly used as a pesticide and a drug, hence increasing the risk of contamination of water supplies. Its intensive use for vector control has led to pollutions in soil and water. Paraoxon is very toxic, with an LD50 of 2 to 30 mg/kg in rats. It can be metabolized in the body from parathion; thus, exposure can lead to serious health effects. In this study, zero valent iron (Fe°/ZVI NPs) nanoparticles were synthesized and investigated for the degradation of Paraoxon, a chemical warfare agent and insecticide, in an aqueous solution. The effects of solution pH, initial pollutant concentration, ZVI NPs dosage and contact time on mineralization efficiency were examined. Batch experiments demonstrated that 15 mg L−1 of Paraoxon was mineralized at degradation efficiencies of 75.9%, 63.9% and 48.9% after three-hour treatment with 6.0, 4.0 and 2.0% w/v Fe°, respectively. The calculated kinetic rate constant kobs was 0.4791 h−1, 0.4519 h−1 and 0.4175 h−1 after treating 10, 15 and 20 mg L−1 of Paraoxon solution with 6.0% w/v Fe, respectively. The degradation dynamics were described by the first-order kinetic law as evidenced by rate constants independent of the initial Paraoxon concentration. The degradation efficiency was strongly dependent on pH, increasing with a decrease in pH, with maximum removal at pH 4. p-nitrophenol was detected as a degradation product, suggesting cleavage of the O-P bond and hydrolysis as possible reaction processes. This study showed that Fe° particles have the potential for degrading Paraoxon. [ABSTRACT FROM AUTHOR]

The enzymatic degradation of pesticides paraoxon (PON) and parathion (PIN) by phosphotriesterase (PTE) has been investigated by QM/MM calculations and MD simulations. In the PTE‐PON complex, Znα and Znβ in the active site are five‐ and six‐coordinated, respectively, while both zinc ions are six coordinated with the Znα‐bound water molecule (WT1) for the PTE‐PIN system. The hydrolytic reactions for PON and PIN are respectively driven by the nucleophilic attack of the bridging‐OH− and the Znα‐bound water molecule on the phosphorus center of substrate, and the two‐step hydrolytic process is predicted to be the rate‐limiting step with the energy spans of 13.8 and 14.4 kcal/mol for PON and PIN, respectively. The computational studies reveal that the presence of the Znα‐bound water molecule depends on the structural feature of substrates characterized by P=O and P=S, which determines the hydrolytic mechanism and efficiency for the degradation of organophosphorus pesticides by PTE. [ABSTRACT FROM AUTHOR]

Background and purpose: Exposure to organophosphorus (OP) compounds may contribute to an increased risk of cognitive impairments and induction of oxidative stress. The present study was designed to evaluate the effects of exposure to paraoxon (the active metabolite of insecticide parathion) on cognitive function and oxidative stress biomarkers. Materials and methods: Adult male Wistar rats (n= 56, 7 per group) were used in this study. Corn oil or paraoxon at 0.3, 0.7, or 1 mg/kg were intraperitoneally administrated. After 14 or 28 days, the animals were examined by Morris water maze to determine spatial learning and memory. The effects of paraoxon on hippocampal glutathione (GSH) and malondialdehyde (MDA) levels were also investigated. Results: Escape latency and swimming distance significantly increased in animals that received 1 mg/kg of paraoxon at both time points (P<0.001 and P<0.05, respectively). In the probe test, animals intoxicated with paraoxon 1 mg/kg spent less time in the target zone and had lower swimming distance and swimming speed compared with the control group. No significant difference was observed in the performance of paraoxon-intoxicated animals in the water maze with visible platform compared with the control group (P>0.05). Exposure to paraoxon 1 mg/kg was associated with decreased GSH and increased MDA levels in the hippocampus. Conclusion: The study showed that exposure to high dose of paraoxon (1 mg/kg) impaired spatial learning and memory independent of any changes in sensorimotor deficit. Induction of oxidative stress plays an important role in development of cognitive impairments caused by exposure to paraoxon. [ABSTRACT FROM AUTHOR]

Organophosphate (OP) nerve agents and pesticides trigger a common mechanism of neurotoxicity resulting from critical targeting and inhibition of acetylcholinesterases (AChE) in central and peripheral synapses in the cholinergic nervous system. Therapeutic countermeasures have thus focused on either administering an oxime post-exposure, that can rapidly reactivate OP-inhibited AChE, or by preventing OP poisoning through administering pre-exposure treatments that scavenge OPs before they inhibit their physiological AChE targets. While several pyridinium aldoxime antidotes are currently approved, their utility is impaired due to their inability to cross the blood-brain barrier (BBB) efficiently. The present study utilized a macaque (Ma) model to demonstrate the efficacy of a novel zwitterionic and centrally acting oxime RS194B to reactivate sarin- and paraoxon-inhibited macaque AChE and butyrylcholinesterase (BChE) in vitro and to further assess the capacity of RS194B to effect a reversal of clinical symptoms following sarin inhalation in vivo. In vitro, oxime reactivation of MaAChE and MaBChE was shown to be comparable to their human orthologs, while the macaque studies indicated that IM administration of 62.5 mg/kg of RS194B and 0.28 mg/kg atropine after continuous exposure to 49.6 μg/kg sarin vapor, rapidly reactivated the inhibited AChE and BChE in blood and reversed both early and advanced clinical symptoms of sarin-induced toxicity following pulmonary exposure within 1 h. The rapid cessation of autonomic and central symptoms, including convulsions, observed in macaques bodes well for the use of RS194B as an intra- or post-exposure human treatment and validates the macaque model in generating efficacy and toxicology data required for approval under the FDA Animal rule.

The search for effective ways of paraoxon (POX) degradation becomes an extremely urgent problem, which can be solved by creating effective bioscavengers in the form of three-dimensional macrocycles. In this work, supramolecular interactions in an aqueous medium were studied between (4-sulfobutyl)-β-cyclodextrin, the hydrophobic cavity of which is capable of binding POX, and viologen calix[4]resorcinol, the cationic groups of which are able to facilitate the nucleophilic attack on the phosphorus atom of the pesticide. A complex of physicochemical methods revealed the nature of the interactions between these cyclodextrin and calix[4]resorcinol, as a result of which the spontaneous formation of nanoparticles occurs. The kinetics of POX hydrolysis reaction using these nanoparticles was studied at room temperature in aqueous Tris-buffer medium by spectrophotometric method. Pure cyclodextrin does not exhibit catalytic activity in the POX hydrolysis, but its presence in a mixture with calix[4]resorcinol leads to a fivefold increase in the hydrolysis rate constant compared to pure calix[4]resorcinol. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • This research introduces a novel electrochemical sensor for detecting ethyl paraoxon, a hazardous pesticide, in food samples. The sensor utilizes sodium titanate nanoribbons (MNR) derived from titanium carbide (Ti 3 C 2) MXene, marking the first report of such an application for MXene derivatives. • The MNRs were synthesized through a facile hydrothermal method, and their structure and composition were confirmed using various techniques like powder XRD, FE-SEM, EDS, HR-TEM, and SAED. • The research then explores the electrochemical properties of the MNRs for ethyl paraoxon detection using cyclic voltammetry (CV), linear sweep voltammetry (LSV), and differential pulse voltammetry (DPV). • The developed sensor demonstrates impressive performance with a remarkably low limit of detection (LOD) of 0.22 nM, a wide detection range spanning from 0.69 nM to 174.03 nM, and a high sensitivity of 0.707 µA/nM/cm2. Furthermore, the sensor effectively detects ethyl paraoxon even in complex matrices like vegetable extracts from tomatoes and beans. • This research paves the way for utilizing MXene-derived nanoribbons for practical applications in food safety monitoring. The facile synthesis, excellent sensitivity, and ability to detect pesticides in real-world samples make this sensor a promising candidate for ensuring food quality. This study reports the development of MXene (Ti 3 C 2 T x) derived sodium titanate nanoribbon-based electrochemical sensor for pesticide detection. Titanium Carbide (Ti 3 C 2) MXene-derived sodium titanate nanoribbon (MNR) was obtained by facile hydrothermal synthesis and characterized by powder X-ray Diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray analysis (EDS) and, high-resolution transmission electron microscopy (HR-TEM). The synthesized water-dispersed MNR was stabilized with Nafion and deposited on the surface of glassy carbon electrodes (GCE), which provide a symmetrical uniform electrode surface. Further, the electrodes were electrochemically characterized with cyclic voltammetry (CV), differential pulse voltammetry (DPV), linear sweep voltammetry (LSV), and electrochemical impedance spectroscopy (EIS). The electrochemical sensing of ethyl paraoxon was carried out in 0.1 M phosphate buffer (PB) by CV, LSV, and DPV. The developed electrochemical sensor exhibited a limit of detection (LOD) of 0.22 nM, a very wide detection range from 0.69 nM to 174.03 nM, and a reliable sensitivity of 0.707 µA/nM/cm2. Moreover, the developed sensor was also employed for the detection of ethyl paraoxon in real samples (vegetable extract spiked with the pesticide). The results suggest that the developed MNR-based sensor would be a potential approach for efficient and accurate detection of ethyl paraoxon in ambient samples, with minimal interference. [ABSTRACT FROM AUTHOR]

The nanosized MgO (Mw‐MgO) was synthesized from Mg(OH)2 gel precursor via a microwave‐assisted sol‐gel hydrothermal method. Compared with the commercial MgO, the optimum Mw‐MgO was obtained by the calcining temperature at 500 °C, and the grain size was about 8.31 nm with a higher surface area of 213.5 m2/g. Meanwhile, such as‐prepared Mw‐MgO showed an excellent performance towards paraoxon degradation, and the maximum degradation amount was up to 43.62 mg/g@90 min at room temperature. The kinetic degradation trend was consistent with the pseudo‐second‐order model (R2>0.99). The degradation mechanism of such Mw‐MgO was also revealed by using nitro blue tetrazolium (NBT) as a probe. [ABSTRACT FROM AUTHOR]

Biosensors containing cholinesterase are analytical devices suitable for the assay of neurotoxic compounds. In the research on biosensors, a new platform has appeared some years ago. It is the digital photography and scoring of coloration (photogrammetry). In this paper, a colorimetric biosensor is constructed using 3D-printed multiwell pads treated with indoxylacetate as a chromogenic substrate and gold nanoparticles with the immobilized enzyme butyrylcholinesterase. A smartphone camera served for photogrammetry. The biosensor was tested for the assay of carbofuran and paraoxon ethyl as two types of covalently binding inhibitors: irreversible and pseudoirreversible. The biosensor exerted good sensitivity to the inhibitors and was able to detect carbofuran with a limit of detection for carbofuran 7.7 nmol/l and 17.6 nmol/l for paraoxon ethyl. A sample sized 25 μl was suitable for the assay lasting approximately 70 minutes. Up to 121 samples can be measured contemporary using one multiwell pad. The received data fully correlated with the standard spectrophotometry. The colorimetric biosensor exerts promising specifications and appears to be competitive to the other analytical procedures working on the principle of cholinesterase inhibition. Low-cost, simple, and portable design represent an advantage of the assay of the biosensor. Despite the overall simplicity, the biosensor can fully replace the standard spectroscopic methods. [ABSTRACT FROM AUTHOR]

Introduction: Oganophosphorus compounds (OP) bind to acetylcholinesterase (AChE) and inactivate it. In the synaptic cleft, undestroyed and accumulated acetylcholine produce the acute cholinergic effects. The aim of this study was to determine the frequency, speed of onset and intensity of certain signs of paraoxon poisoning depending on dose and outcome of poisoning. Methods: The study was conducted in adult Wistar rats. The median lethal dose (LD50) of paraoxon as well as protective ratio (PR) of atropine (10 mg/kg intramuscularly) was determined. Clinical signs of poisoning were observed: fasciculations, tremor, seizures, ataxia, piloerection, lacrimation, exophthalmos, bizzare/stereotypic behaviour and dyspnoea. The time from paraoxon injection to the first appearance of the sign of poisoning was recorded as well as the intensity of poisoning with evaluation at 10 time intervals throughout the 4 h observational period. Results: The LD50 of paraoxon was 0.33 mg/kg (subcutaneously) and PR of atropine was 2.73. Dose-dependent, piloerection occurred more often (p = 0.009) and at higher intensity (p = 0.016) at higher doses. Fasciculations, tremor, seizures and ataxia occurred significantly earlier at higher doses of paraoxon (p = 0.015, 0.002, 0.021 and 0.016, respectively), as well as the intensity of seizure, tremor and fasciculation. Piloerection (p = 0.002) and seizures occurred more frequently (p = 0.009) in non-survivors. Fasciculations, tremor, seizures and ataxia occurred significantly earlier and at higher intensity in non-survivors (p < 0.001, for all parameters), as well as dyspnoea (p = 0.009 and p = 0.048). In atropine-protected rats, nicotinic effects persevered, so they were the prognostic parameter of the severity of the poisoning. Conclusion: Seizures and fasciculations followed by tremor were strong prognostic parameters of the probability of lethal outcome of paraoxon poisoning. Also, the mentioned poisoning signs were with their intensity and speed of occurrence in a clear positive correlation with the administered dose of paraoxon. Even at high doses of paraoxon, atropine blocked the muscarinic (but not nicotinic) effects and somewhat mitigated the CNS toxic effects.

The hydroxyl oxygen of the catalytic triad serine in the active center of serine hydrolase acetylcholinesterase (AChE) attacks organophosphorus compounds (OPs) at the phosphorus atom to displace the primary leaving group and to form a covalent bond. Inhibited AChE can be reactivated by cleavage of the Ser-phosphorus bond either spontaneously or through a reaction with nucleophilic agents, such as oximes. At the same time, the inhibited AChE adduct can lose part of the molecule by progressive dealkylation over time in a process called aging. Reactivation of the aged enzyme has not yet been demonstrated. Here, our goal was to study oxime reactivation and aging reactions of human AChE inhibited by mipafox or a sarin analog (Flu-MPs, fluorescent methylphosphonate). Progressive reactivation was observed after Flu-MPs inhibition using oxime 2-PAM. However, no reactivation was observed after mipafox inhibition with 2-PAM or the more potent oximes used. A peptide fingerprinted mass spectrometry (MS) method, which clearly distinguished the peptide with the active serine (active center peptide, ACP) of the human AChE adducted with OPs, was developed by MALDI-TOF and MALDI-TOF/TOF. The ACP was detected with a diethyl-phosphorylated adduct after paraoxon inhibition, and with an isopropylmethyl-phosphonylated and a methyl-phosphonylated adduct after Flu-MPs inhibition and subsequent aging. Nevertheless, nonaged nonreactivated complexes were seen after mipafox inhibition and incubation with oximes, where MS data showed an ACP with an NN diisopropyl phosphoryl adduct. The kinetic experiments showed no reactivation of activity. The computational molecular model analysis of the mipafox-inhibited hAChE plots of energy versus distance between the atoms separated by dealkylation showed a high energy demand, thus little aging probability. However, with Flu-MPs and DFP, where aging was observed in our MS data and in previously published crystal structures, the energy demand calculated in modeling was lower and, consequently, aging appeared as a more likely reaction. We document here direct evidence for a phosphorylated hAChE refractory to oxime reactivation, although we observed no aging.

Abstract Background Excessive inflammation might activate and injure the blood-brain barrier (BBB), a common feature of many central nervous system (CNS) disorders. We previously developed an in vitro BBB injury model in which the organophosphate paraoxon (PX) affects the BBB endothelium by attenuating junctional protein expression leading to weakened barrier integrity. The objective of this study was to investigate the inflammatory cellular response at the BBB to elucidate critical pathways that might lead to effective treatment in CNS pathologies in which the BBB is compromised. We hypothesized that caspase-1, a core component of the inflammasome complex, might have important role in BBB function since accumulating evidence indicates its involvement in brain inflammation and pathophysiology. Methods An in vitro human BBB model was employed to investigate BBB functions related to inflammation, primarily adhesion and transmigration of peripheral blood mononuclear cells (PBMCs). Caspase-1 pathway was studied by measurements of its activation state and its role in PBMCs adhesion, transmigration, and BBB permeability were investigated using the specific caspase-1 inhibitor, VX-765. Expression level of adhesion and junctional molecules and the secretion of pro-inflammatory cytokines were measured in vitro and in vivo at the BBB endothelium after exposure to PX. The potential repair effect of blocking caspase-1 and downstream molecules was evaluated by immunocytochemistry, ELISA, and Nanostring technology. Results PX affected the BBB in vitro by elevating the expression of the adhesion molecules E-selectin and ICAM-1 leading to increased adhesion of PBMCs to endothelial monolayer, followed by elevated transendothelial-migration which was ICAM-1 and LFA-1 dependent. Blocking caspase-8 and 9 rescued the viability of the endothelial cells but not the elevated transmigration of PBMCs. Inhibition of caspase-1, on the other hand, robustly restored all of barrier insults tested including PBMCs adhesion and transmigration, permeability, and VE-cadherin protein levels. The in vitro inflammatory response induced by PX and the role of caspase-1 in BBB injury were corroborated in vivo in isolated blood vessels from hippocampi of mice exposed to PX and treated with VX-765. Conclusions These results shed light on the important role of caspase-1 in BBB insult in general and specifically in the inflamed endothelium, and suggest therapeutic potential for various CNS disorders, by targeting caspase-1 in the injured BBB.

In this study; Nano enzyme system based sensor system has been developed for detection of nerve agents used in chemical weapons production. The chemical substances forming the nerve agents are included in the group of organophosphorus compounds. Paraoxon was used as the organophosphorus compound. Paraoxon molecule irreversibly inhibits the acetylcholinesterase enzyme (AChE). In this respect, it is preferred because of its similarity to nerve agents. In the sensor system, nano enzyme system synthesized according to photosensitive cross-linking method with ruthenium based amino acid monomers was used as sensor layer. The fluorescence spectrum of the obtained nano enzyme was taken and observed to show fluorescence. As a result of the analyzes, working conditions were determined as wavelength of 300 nm and pH of 7,4. The fluorescence intensities of the paraoxon samples, which ranged from 0.01 ppm to 200 ppm, were measured after interaction with the nano-enzyme at 300 nm wavelength and 7.4 pH. Calibration graph is drawn by using the obtained data. According to the experimental results, the LOD value of the sensor system based on the Nano AChE enzyme was calculated as 6,0x10-8 M, and the LOQ was calculated as 6,98x10-8M.

The preparation of MgO nanoparticles with relatively small sizes and highly active surface areas is still a great challenge nowadays. The principal objective of this work was to investigate and optimize the calcined conditions of MgO with smaller sizes and higher surface areas, which contributed to its better degradation ability towards paraoxon pollutants. Firstly, the aerogel Mg(OH)2 nanosheets with an increased surface area of 349.0 m2/g was prepared via a combined sol–gel-hydrothermal method. Then the calcined MgO nanoparticles with different morphology, size dimensions, and specific surface areas were obtained at different calcination temperatures from 400 to 800 °C. The optimized average grain size of MgO obtained at 600 °C was achieved to 8.7 ± 3.2 nm with a relatively high surface area up to 231.4 m2/g. Meanwhile, such as-prepared MgO nanoparticles showed an excellent performance towards paraoxon degradation, and the maximum degradation amount of paraoxon-ethyl was up to 57.8 mg/g@90 min at room temperature. The kinetics of degradation was consistent with the pseudo-second-order model (R2 > 0.99). Such excellent degradation capacity was derived from more generations of superoxide radical (•O2−) sites as revealed by using the nitro blue tetrazolium (NBT) as a probe. The results indicated that the MgO nanoparticles reported herein could be an effective candidate for the environmental remediation of organophosphorus toxin pollutants due to their facile scale-up, low cost, eco-friendly characteristic, and high removal efficiency. [ABSTRACT FROM AUTHOR]

Background: Identification of modifiable risk factors that affect cognitive decline is important for the development of preventive and treatment strategies. Status of paraoxonase 1 (PON1), a high-density lipoprotein-associated enzyme, may play a role in the development of neurological diseases, including Alzheimer's disease.Objective: We tested a hypothesis that PON1 status predicts cognition in individuals with mild cognitive impairment (MCI).Methods: Individuals with MCI (n = 196, 76.8-years-old, 60% women) participating in a randomized, double-blind placebo-controlled trial (VITACOG) were assigned to receive a daily dose of folic acid (0.8 mg), vitamin B12 (0.5 mg) and B6 (20 mg) (n = 95) or placebo (n = 101) for 2 years. Cognition was analyzed by neuropsychological tests. Brain atrophy was quantified in a subset of participants (n = 168) by MRI. PON1 status, including PON1 Q192R genotype, was determined by quantifying enzymatic activity of PON1 using paraoxon and phenyl acetate as substrates.Results: In the placebo group, baseline phenylacetate hydrolase (PhAcase) activity of PON1 (but not paraoxonase activity or PON1 Q192R genotype) was significantly associated with global cognition (Mini-Mental State Examination, MMSE; Telephone Inventory for Cognitive Status-modified, TICS-m), verbal episodic memory (Hopkins Verbal Learning Test-revised: Total Recall, HVLT-TR; Delayed Recall, HVLT-DR), and attention/processing speed (Trail Making A and Symbol Digits Modalities Test, SDMT) at the end of study. In addition to PhAcase, baseline iron and triglycerides predicted MMSE, baseline fatty acids predicted SDMT, baseline anti-N-Hcy-protein autoantibodies predicted TICS-m, SDMT, Trail Making A, while BDNF V66M genotype predicted HVLT-TR and HVLT-DR scores at the end of study. B-vitamins abrogated associations of PON1 and other variables with cognition.Conclusion: PON1 is a new factor associated with impaired cognition that can be ameliorated by B-vitamins in individuals with MCI. [ABSTRACT FROM AUTHOR]

Accidents with toxic industrial chemicals and threats posed by chemical warfare agents, as organophosphorus nerve agents and blistering agents, has become an increasing concern over the last decades. Intoxication is not only due to inhalation but dermal route can also be important and can quickly lead to death. It is therefore crucial to have suitable means of personal protection and decontamination. Some are already commercially available but often present drawbacks. Efforts have been made to develop new systems and several studies have shown the interest of metallic nanoparticles. The challenge remains to entrap the particles in an adapted matrix to limit their diffusion in the immediate environment, while preserving the bare particles decontamination efficacy. In this study, an easy to handle peelable gel, incorporating CeO 2 nanoparticles has been developed for efficient skin decontamination against toxic chemicals. The main objective has been to make it suitable in any context of application (battlefield or civil exposure). Nano-octahedra (NO) CeO 2 particles synthetized in this study have been able to increase the degradation of paraoxon, a simulant warfare agent in liquid media. NO have then been incorporated in a peelable gel, the formulation has been optimized through design of experiments and its physico-chemical properties characterized. Even after incorporation to the gel, NO retained their neutralization properties. The formulation efficiency towards neutralization and skin decontamination have been evaluated in vitro on Franz diffusion cells. The interest of the peelable gel have been clearly demonstrated with a decrease by about 5-fold of the quantity of POX absorbed into the skin and a decrease of 3–4-fold in the viable skin, which was much higher than the use of cotton or nanoparticles as powder. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • A dual-detection paper-based device (PAD) for selective OPs analysis was presented. • LDI-MS, complementary to colorimetry, enables selective and trace analysis of OPS. • LDI-MS enhances the sensitivity with a 5 ppb LOD of OPs. A dual detection platform including colorimetry and LDI-MS was implemented with a 3D paper-based analytical device (PAD) for highly selective and sensitive detection of organophosphates (OPs). The colorimetric approach based on the inhibition assay of acetylcholinesterase (AChE) activity by OPs was employed for preliminary testing/screening of the presence of OPs and performing quantitative analysis of total OPs. Limit of detections (LODs) from colorimetric assay were 0.006 and 0.01 mg L−1 for dichlorvos and paraoxon, respectively, which were sufficient to monitor the OPs at the maximum residues levels (MRLs). However, LDI-MS as a complementary detection technique was further exploited to differentiate the type of OPs and quantify the amount of individual OPs at trace concentrations. With LDI-MS, the detection sensitivity was enhanced with extremely low LODs of 5 µg/L for both dichlorvos and paraoxon. This dual detection platform has shown its performance for determination of dichlorvos and paraoxon in cabbage, broccoli and grape with satisfied accuracy and precision. [ABSTRACT FROM AUTHOR]

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]

Properties of paraoxon, such as poor water solubility, low rate of natural decomposition, ability to accumulate in soil and wastewater, lead to the fact that paraoxon is found in various agricultural products and textiles. In this regard, the search for effective ways of paraoxon degradation becomes an extremely urgent problem, which can be solved by creating catalysts by mimicking paraxonase. In this work, a complex of physicochemical methods was used to study the supramolecular interactions of sodium alginate, which has a calcium-binding ability similar to paraxonase, with viologen calix[4]resorcinol and to reveal the nature of the intermolecular interactions between them resulting in the spontaneous formation of nanoparticles. Before proceeding to the investigation of the binding ability of obtained nanoparticles to paraoxon, the encapsulating effect of nanoparticles on a number of model substrates of different solubility (doxorubicin hydrochloride, quercetin and oleic acid) was studied. The kinetics of paraoxon hydrolysis reaction using these nanoparticles was studied at room temperature in an aqueous medium by spectrophotometric method. The rate of this reaction increases with increasing concentration of stable nanoparticles having hydrophobic domains that ensure paraoxon immobilization. The results obtained allow considering the supramolecular polysaccharide/calixarene system as an effective biomimetic catalyst. [Display omitted] • Sodium alginate and viologen calixarene self-assemble into nanoparticles. • Calixarene orders the polymer into stable and spherical nanoparticles. • Alginate–calixarene nanoparticles encapsulate hydrophilic and hydrophobic cargos. • Alginate–calixarene nanoparticles decompose paraoxon under mild conditions. [ABSTRACT FROM AUTHOR]