Reactivators of acetylcholinesterase inhibited by organophosphorus nerve agents

Morphology Regulation of UiO-66-2I Supporting Systematic Investigations of Shape-Dependent Catalytic Activity for Degradation of an Organophosphate Nerve Agent Simulant

Phosphonate-based nerve agents, as a kind of deadly chemical warfare agent, are a persistent and evolving threat to humanity. Zirconium-based metal-organic frameworks (Zr-MOFs) are a kind of highly porous crystalline material that includes Zr-OH-Zr sites and imitates the active sites of the phosphotriesterase enzyme, representing significant potential for the adsorption and catalytic hydrolysis of phosphonate-based nerve agents. In this work, we present a new Zr-MOF, UiO-66-2I, which attaches two iodine atoms in the micropore of the MOF and exhibits excellent catalytic activity on the degradation of a nerve agent simulant, dimethyl 4-nitrophenyl phosphate (DMNP), as the result of the formation of halogen bonds between the phosphate ester bonds and iodine groups. Furthermore, various morphologies of UiO-66-2I, such as blocky-shaped nanoparticles (NPs), two-dimensional (2D) nanosheets, hexahedral NPs, stick-like NPs, colloidal microspheres, and colloidal NPs, have been obtained by adding acetic acid (AA), formic acid (FA), propionic acid (PA), valeric acid (VA), benzoic acid (BA), and trifluoroacetic acid (TFA) as modulators, respectively, and show different catalytic hydrolysis activities. Specifically, the catalytic activities follow the trend UiO-66-2I-FA (t1/2 = 1 min) > UiO-66-2I-AA-NP (t1/2 = 4 min) ≈ UiO-66-2I-VA (t1/2 = 4 min) > UiO-66-2I-BA (t1/2 = 5 min) > UiO-66-2I-PA (t1/2 = 15 min) > UiO-66-2I-TFA (t1/2 = 18 min). The experimental results show that the catalytic hydrolysis activity of Zr-MOF is regulated by the crystallinity, defect quantity, morphologies, and hydrophilicity of these samples, which synergistically affect the accessibility of catalytic sites and the diffusion of phosphate in the pores of Zr-MOFs.

Reactivation by novel pyridinium oximes of rat serum and skeletal muscle acetylcholinesterase inhibited by organophosphates

The treatment of organophosphate (OP) anticholinesterases currently lacks an effective oxime reactivator of OP-inhibited acetylcholinesterase (AChE) which can penetrate the blood-brain barrier (BBB). Our laboratories have synthesized novel substituted phenoxyalkyl pyridinium oximes and tested them for their ability to promote survival of rats challenged with lethal doses of nerve agent surrogates. These previous studies demonstrated the ability of some of these oximes to promote 24-h survival to rats challenged with a lethal level of highly relevant surrogates for sarin and VX. The reactivation of OP-inhibited AChE in peripheral tissues was likely to be a major contributor to their efficacy in survival of lethal OP challenges. In the present study, twenty of these novel oximes were screened in vitro for reactivation ability for AChE in rat skeletal muscle and serum using two nerve agent surrogates: phthalimidyl isopropyl methylphosphonate (PIMP, a sarin surrogate) and 4-nitrophenyl ethyl methylphosphonate (NEMP, a VX surrogate). The oximes demonstrated a range of 23%-102% reactivation of AChE in vitro across both tissue types. Some of the novel oximes tested in the present study demonstrated the ability to more effectively reactivate AChE in serum than the currently approved oxime, 2-PAM. Therefore, some of these novel oximes have the potential to reverse AChE inhibition in peripheral target tissues and contribute to survival efficacy.

Photoelectrochemical Solution Gated Graphene Field-Effect Transistor Functionalized by Enzymatic Cascade Reaction for Organophosphate Detection

Solution Gated Graphene Field-Effect Transistors (SGGT) are eagerly anticipated as an amplification platform for fabricating advanced ultra-sensitive sensors, allowing significant modulation of the drain current with minimal gate voltage. However, few studies have focused on light-matter interplay gating control for SGGT. Herein, this challenge is addressed by creating an innovative photoelectrochemical solution-gated graphene field-effect transistor (PEC-SGGT) functionalized with enzyme cascade reactions (ECR) for Organophosphorus (OPs) detection. The ECR system, consisting of acetylcholinesterase (AChE) and CuBTC nanomimetic enzymes, selectively recognizes OPs and forms o-phenylenediamine (oPD) oligomers sediment on the PEC electrode, with layer thickness related to the OPs concentration, demonstrating time-integrated amplification. Under light stimulation, the additional photovoltage generated on the PEC gate electrode is influenced by the oPD oligomers sediment layer, creating a differentiated voltage distribution along the gate path. PEC-SGGT, inherently equipped with built-in amplification circuits, sensitively captures gate voltage changes and delivers output with an impressive thousandfold current gain. The seamless integration of these three amplification modes in this advanced sensor allows a good linear range and highly sensitive detection of OPs, with a detection limit as low as 0.05 pm. This work provides a proof-of-concept for the feasibility of light-assisted functionalized gate-controlled PEC-SGGT for small molecule detection.

New Heterostilbene and Triazole Oximes as Potential CNS-Active and Cholinesterase-Targeted Therapeutics

New furan, thiophene, and triazole oximes were synthesized through several-step reaction paths to investigate their potential for the development of central nervous systems (CNS)-active and cholinesterase-targeted therapeutics in organophosphorus compound (OP) poisonings. Treating patients with acute OP poisoning is still a challenge despite the development of a large number of oxime compounds that should have the capacity to reactivate acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). The activity of these two enzymes, crucial for neurotransmission, is blocked by OP, which has the consequence of disturbing normal cholinergic nerve signal transduction in the peripheral and CNS, leading to a cholinergic crisis. The oximes in use have one or two pyridinium rings and cross the brain-blood barrier poorly due to the quaternary nitrogen. Following our recent study on 2-thienostilbene oximes, in this paper, we described the synthesis of 63 heterostilbene derivatives, of which 26 oximes were tested as inhibitors and reactivators of AChE and BChE inhibited by OP nerve agents-sarin and cyclosarin. While the majority of oximes were potent inhibitors of both enzymes in the micromolar range, we identified several oximes as BChE or AChE selective inhibitors with the potential for drug development. Furthermore, the oximes were poor reactivators of AChE; four heterocyclic derivatives reactivated cyclosarin-inhibited BChE up to 70%, and cis,trans-5 [2-((Z)-2-(5-((E)-(hydroxyimino)methyl)thiophen-2-yl)vinyl)benzonitrile] had a reactivation efficacy comparable to the standard oxime HI-6. In silico analysis and molecular docking studies, including molecular dynamics simulation, connected kinetic data to the structural features of these oximes and confirmed their productive interactions with the active site of cyclosarin-inhibited BChE. Based on inhibition and reactivation and their ADMET properties regarding lipophilicity, CNS activity, and hepatotoxicity, these compounds could be considered for further development of CNS-active reactivators in OP poisoning as well as cholinesterase-targeted therapeutics in neurodegenerative diseases such as Alzheimer's and Parkinson's.

4-Amidophenol Quinone Methide Precursors: Effective and Broad-Scope Nonoxime Reactivators of Organophosphorus-Inhibited Cholinesterases and Resurrectors of Organophosphorus-Aged Acetylcholinesterase

Acetylcholinesterase (AChE) inhibition by organophosphorus (OP) compounds poses a serious health risk to humans. While many therapeutics have been tested for treatment after OP exposure, there is still a need for efficient reactivation against all kinds of OP compounds, and current oxime therapeutics have poor blood-brain barrier penetration into the central nervous system, while offering no recovery in activity from the OP-aged forms of AChE. Herein, we report a novel library of 4-amidophenol quinone methide precursors (QMP) that provide effective reactivation against multiple OP-inhibited forms of AChE in addition to resurrecting the aged form of AChE after exposure to a pesticide or some phosphoramidates. Furthermore, these QMP compounds also reactivate OP-inhibited butyrylcholinesterase (BChE) which is an in vivo, endogenous scavenger of OP compounds. The in vitro efficacies of these QMP compounds were tested for reactivation and resurrection of soluble forms of human AChE and BChE and for reactivation of cholinesterases within human blood as well as blood and brain samples from a humanized mouse model. We identify compound 10c as a lead candidate due to its broad-scope efficacy against multiple OP compounds as well as both cholinesterases. With methylphosphonates, compound 10c (250 μM, 1 h) shows >60% recovered activity from OEt-inhibited AChE in human blood as well as mouse blood and brain, thus highlighting its potential for future in vivo analysis. For 10c, the effective concentration (EC50) is less than 25 μM for reactivation of three different methylphosphonate-inhibited forms of AChE, with a maximum reactivation yield above 80%. Similarly, for OP-inhibited BChE, 10c has EC50 values that are less than 150 μM for two different methylphosphonate compounds. Furthermore, an in vitro kinetic analysis show that 10c has a 2.2- and 92.1-fold superior reactivation efficiency against OEt-inhibited and OiBu-inhibited AChE, respectively, when compared to an oxime control. In addition to 10c being a potent reactivator of AChE and BChE, we also show that 10c is capable of resurrecting (ethyl paraoxon)-aged AChE, which is another current limitation of oximes.

Uncharged mono- and bisoximes: In search of a zwitterion to countermeasure organophosphorus intoxication

The current study imposes a new class of organophosphorus (OP)-inhibited cholinesterase reactivators by conceptualizing a family of asymmetric bisoximes with various reactivating scaffolds. Several novel nucleophilic warheads were investigated, putting forward 29 novel reactivating options, by evaluating their nucleophilicity and ability to directly decompose OP compounds. Adopting the so-called zwitterionic strategy, 17 mono-oxime and nine bisoxime reactivators were discovered with major emphasis on the bifunctional-moiety approach. Compounds were compared with clinically used standards and other known experimentally highlighted reactivators. Our results clearly favor the concept of asymmetric bisoximes as leading reactivators in terms of efficacy and versatility. These top-ranked compounds were characterized in detail by reactivation kinetics parameters and evaluated for potential CNS availability. The highlighted molecules 55, 57, and 58 with various reactivating warheads, surpassed the reactivating potency of pralidoxime and several notable uncharged reactivators. The versatility of lead drug candidate 55 was also inspected on OP-inhibited butyrylcholinesterase, revealing a much higher rate compared to existing clinical antidotes.

Screening of efficient salicylaldoxime reactivators for DFP and paraoxon-inhibited acetylcholinesterase

Previously we reported two salicylaldoxime conjugates (L7R3 and L7R5) showing equal or even higher reactivating efficiency for both organophosphorus nerve agent and pesticide inhibited acetylcholinesterase in comparison to obidoxime and HI-6. In this study, L7R3 and L7R5 were selected as lead compounds and refined by employing a fragment-based drug design strategy, and a total of 32 novel salicylaldoxime conjugates were constructed and screened for DFP and paraoxon inhibited acetylcholinesterase. The findings demonstrate that the conjugate L73R3, which contains a 4-nitrophenyl group, exhibited a higher reactivation efficacy against paraoxon-inhibited acetylcholinesterase compared to obidoxime and HI-6. It was confirmed that the combination of a 4-pyridinyl or 4-nitrophenyl peripheral site ligand, a piperazine linker and a methyl or chloro-substituted salicylaldoxime could construct efficient nonquaternary oxime reactivators. The results hold promise for developing a new generation of highly effective antidotes for organophosphate poisoning.

Smart Sensing of Nerve Agents

The recent international scenario highlights the importance to protect human health and environmental quality from toxic compounds. In this context, organophosphorous (OP) Nerve Agents (NAs) have received particular attention, due to their use in terrorist attacks. Classical instrumental detection techniques are sensitive and selective, but they cannot be used in real field due to the high cost, specialized personnel requested and huge size. For these reasons, the development of practical, easy and fast detection methods (smart methods) is the future of this field. Indeed, starting from initial sensing research, based on optical and/or electrical sensors, today the development and use of smart strategies to detect NAs is the current state of the art. This review summarizes the smart strategies to detect NAs, highlighting some important parameters, such as linearity, limit of detection and selectivity. Furthermore, some critical comments of the future on this field, and in particular, the problems to be solved before a real application of these methods, are provided.

Detoxification of V-Nerve Agents Assisted by a Microperoxidase: New Pathway Revealed by the Use of a Relevant VX Simulant

The biocatalyzed oxidative detoxification of the V-series simulant PhX, by mean of the microperoxidase AcMP11, affords the corresponding phosphonothioate as the prominent product instead of the classical P-S and P-O bond cleavage. While PhX is structurally very close to the live agent VX (the methyl group is replaced by a phenyl), assessment with other surrogates missing the nucleophilic amino function displayed more resistance under the same conditions with no phosphonothioate observed. These encouraging results highlight 1) the efficacy of AcMP11 microperoxidase to efficiently detoxify V-series organophosphorus nerve agents (OPNA), and 2) the necessity to use representative alkyl or aryl phosphonothioates simulants such as PhX bearing the appropriate side chain as well as the P-O and P-S cleavable bond to mimic accurately the V-series OPNA to prevent false positive or false negative results.

A pyrene-based chromo-fluorogenic probe for specific detection of sarin gas mimic, diethylchlorophosphate

Nerve agents are becoming serious issues for the healthy and sustainable environment of modern civilization. Therefore, its detection and degradation are of paramount importance to the scientific community. In the present contribution, we have introduced a chromo-fluorogenic pyrene-based  probe, (E)-2-methoxy-3-(pyren-1-ylimino)-3,8a-dihydro-2H-chromen-4-ol (PMCO) to detect sarin stimulant diethylchlorophosphate (DCP) in solution and gaseous phases. On inserting DCP in PMCO solution, a visual colorimetric change from yellow to clear colourless in daylight and highly intensified blue fluorescence was observed instantly under a 365 nm portable UV lamp light. PMCO has outstanding selectivity and high sensitivity with a limit of detection of 1.32 μM in dimethyl sulfoxide (DMSO) medium and 77.5 nM in 20% H2O-DMSO. A handy strained paper strip-based experiment was demonstrated to recognize DCP in a mixture of similar toxic analytes. A dip-stick experiment was performed to identify DCP vapour, and may be used as an effective photonic tool. We also demonstrated real sample analysis utilizing different DCP-spiked water samples and validating DCP detection even in various types of soils such as sand, field, and mud. Therefore, this present study provides an effective chemosensor for instant and on-site detection of toxic nerve agents in dangerous circumstances.

Recent advances in cholinergic mechanisms as reactions to toxicity, stress, and neuroimmune insults

This review presents recent studies of the chemical and molecular regulators of acetylcholine (ACh) signaling and the complexity of the small molecule and RNA regulators of those mechanisms that control cholinergic functioning in health and disease. The underlying structural, neurochemical, and transcriptomic concepts, including basic and translational research and clinical studies, shed new light on how these processes inter-change under acute states, age, sex, and COVID-19 infection; all of which modulate ACh-mediated processes and inflammation in women and men and under diverse stresses. The aspect of organophosphorus (OP) compound toxicity is discussed based on the view that despite numerous studies, acetylcholinesterase (AChE) is still a vulnerable target in OP poisoning because of a lack of efficient treatment and the limitations of oxime-assisted reactivation of inhibited AChE. The over-arching purpose of this review is thus to discuss mechanisms of cholinergic signaling dysfunction caused by OP pesticides, OP nerve agents, and anti-cholinergic medications; and to highlight new therapeutic strategies to combat both the acute and chronic effects of these chemicals on the cholinergic and neuroimmune systems. Furthermore, OP toxicity was examined in view of cholinesterase inhibition and beyond in order to highlight improved small molecules and RNA therapeutic strategies and assess their predicted pitfalls to reverse the acute toxicity and long-term deleterious effects of OPs.

A single post-exposure oxime RS194B treatment rapidly reactivates acetylcholinesterase and reverses acute symptoms in macaques exposed to diethylphosphorothioate parathion and chlorpyrifos insecticides

Millions of individuals globally suffer from inadvertent, occupational or self-harm exposures from organophosphate (OP) insecticides, significantly impacting human health. Similar to nerve agents, insecticides are neurotoxins that target and inhibit acetylcholinesterase (AChE) in central and peripheral synapses in the cholinergic nervous system. Post-exposure therapeutic countermeasures generally include administration of atropine with an oxime to reactivate the OP-inhibited AChE. However, animal model studies and recent clinical trials using insecticide-poisoned individuals have shown minimal clinical benefits of the currently approved oximes and their efficacy as antidotes has been debated. Currently used oximes either reactivate poorly, do not readily cross the blood-brain barrier (BBB), or are rapidly cleared from the circulation and must be repeatedly administered. Zwitterionic oximes of unbranched and simplified structure, for example RS194B, have been developed that efficiently cross the BBB resulting in reactivation of OP-inhibited AChE and dramatic reversal of severe clinical symptoms in mice and macaques exposed to OP insecticides or nerve agents. Thus, a single IM injection of RS194B has been shown to rapidly restore blood AChE and butyrylcholinesterase (BChE) activity, reverse cholinergic symptoms, and prevent death in macaques following lethal inhaled sarin and paraoxon exposure. The present macaque studies extend these findings and assess the ability of post-exposure RS194B treatment to counteract oral poisoning by highly toxic diethylphosphorothioate insecticides such as parathion and chlorpyrifos. These OPs require conversion by P450 in the liver of the inactive thions to the active toxic oxon forms, and once again demonstrated RS194B efficacy to reactivate and alleviate clinical symptoms within 60 mins of a single IM administration. Furthermore, when delivered orally, the Tmax of RS194B at 1-2 h was in the same range as those administered IM but were maintained in the circulation for longer periods greatly facilitating the use of RS194B as a non-invasive treatment, especially in isolated rural settings.

Highly selective and sensitive chromogenic recognition of sarin gas mimicking diethylchlorophosphate

The high-level toxic effects of organophosphate (OP) nerve agents severely threaten national security and public health. Generating trustworthy, accurate methods for quickly identifying these poisonous chemicals is urgently necessary. In this study, we have presented an azine-based colorimetric sensor (HBD) for the highly sensitive and selective identification of poisonous sarin gas surrogate diethylchlorophosphate (DCP). Our introduced sensor shows a purple color in contact with DCP, which is fully reversible upon the addition of triethylamine (TEA). The detection limit of our sensor for the toxic nerve agent mimic DCP is in the μM range. We have fabricated a test kit to verify the capability of HBD for on-the-spot identification of DCP to execute its practical use. To prove that HBD is an effective chemosensor, dip-stick investigation was conducted to detect DCP in the vaporous stage in the presence of different OPs, inorganic phosphates (IPs), and many other deadly analytes. A cellphone-based display method was also undertaken for on-the-spot recognition and measurement of DCP in isolated regions.

AChE activity self-breathing control mechanisms regulated by H2Sn and GSH: Persulfidation and glutathionylation on sulfhydryl after disulfide bonds cleavage

Hydrogen sulfide (H2S), or dihydrogen sulfane (H2Sn), acts as a signal molecule through the beneficial mechanism of persulfidation, known as the post-translational transformation of cysteine residues to persulfides. We previously reported that Glutathione (GSH) could regulate enzyme activity through S-desulfurization or glutathionylation of residues to generate protein-SG or protein-SSG, releasing H2S. However, little is known about the mechanisms by which H2Sn and GSH affect the disulfide bonds. In this study, we provide direct evidences that H2Sn and GSH modify the sulfhydryl group on Cys272, which forms disulfide bonds in acetylcholinesterase (AChE), to generate Cys-SSH and Cys-SSG, respectively. Glutathionylation of disulfide is a two-step reaction based on nucleophilic substitution, in which the first CS bond is broken, then the SS bond is broken to release H2S. H2Sn and GSH controlled self-breathing motion in enzyme catalysis by disconnecting specific disulfide bonds and modifying cysteine residues, thereby regulating AChE activity. Here, we elucidated H2Sn and GSH mechanisms on disulfide in the AChE system and proposed a self-breathing control theory induced by H2Sn and GSH. These theoretical findings shed light on the biological functions of H2Sn and GSH on sulfhydryl and disulfide bonds and enrich the theory of enzyme activity regulation.

Novichok Nerve Agents as Inhibitors of Acetylcholinesterase-In Silico Study of Their Non-Covalent Binding Affinity

In silico studies were performed to assess the binding affinity of selected organophosphorus compounds toward the acetylcholinesterase enzyme (AChE). Quantum mechanical calculations, molecular docking, and molecular dynamics (MD) with molecular mechanics Generalized-Born surface area (MM/GBSA) were applied to assess quantitatively differences between the binding energies of acetylcholine (ACh; the natural agonist of AChE) and neurotoxic, synthetic correlatives (so-called "Novichoks", and selected compounds from the G- and V-series). Several additional quantitative descriptors like root-mean-square fluctuation (RMSF) and the solvent accessible surface area (SASA) were briefly discussed to give-to the best of our knowledge-the first quantitative in silico description of AChE-Novichok non-covalent binding process and thus facilitate the search for an efficient and effective treatment for Novichok intoxication and in a broader sense-intoxication with other warfare nerve agents as well.

Adsorptive stripping voltammetric sensor based on Cd zeolitic imidazole framework-67 for electrochemical detection of sarin simulant

A selective and reliable modified glassy carbon sensor, based on a 1.0% Cd zeolitic imidazole framework-67 modified glassy carbon sensor (GCS2), has been developed for ultrasensitive detection of dimethyl methyl phosphonate (DMMP) in human biological fluid. The synthesis of porous nanoparticles of Cd zeolitic imidazole framework-67 (Cd ZIF-67) was carried out via the hydrothermal method. The resulting Cd ZIF-67 powder emerges with good crystallinity, a rhombic dodecahedral morphology with particle size in the range 300 ~ 500 nm, and a specific surface area of 1780 m2·g-1. Furthermore, the fabricated sensor exhibited superior performance in the detection of DMMP with two linearity ranges of 0.02-2.0 nM and 2.0-9.0 nM and a limit of detection (LOD) of 0.06 pM. The fabricated sensor exhibited good reliability, long-term stability, and repeatability, which are favourable attributes for electroanalytical detection. In addition, the fabricated sensor displayed superior performance without significant interference during the assay of DMMP in a biological fluid (human serum sample) within two linearity ranges of 0.1-1.0 nM and 1.0-6.0 nM and a LOD of 0.03 nM.

Comprehensive insight on protein modification by V-type agent: A chemical proteomic approach employing bioorthogonal reaction

Organophosphorus compounds (OPs) such as chemical agents and pesticides are posing critical threats to civilians due to their irreversible phosphonylation of diverse amino acids residues forming different protein adducts. However, traditional analytical approaches are quite limited in capturing the myriad of post-translational events that affect protein functions, especially in identifying the low-abundance OP adducts. Herein a systematic proteomic strategy based on a typical click-enrich-release-identify bioorthogonal operation was firstly developed by employing an alkynyl-tagged V-type agent probe (AVP) and a biotin-based azido-enrichment linker (BTP-N3 ). AVP targeting peptides from human serum albumin (HSA) or plasma were captured by BTP-N3 via CuAAC click reaction, enriched by streptavidin beads, released by selective alkaline hydrolysis of phenacyl ester bond, and subsequently sequenced by LC-MS/MS. This strategy has helped identifying 1115 unique OP adduction sites on 163 proteins in human plasma, and covers lots of OP adducts that cannot be achieved by traditional detection methods. The comprehensive coverage of novel OP substrates provided a general and sensitive approach to retrospective verification and/or dose assessment of toxic OPs.

Starch Assisted the ZnS Buffer Layer in Enhancing the Photoluminescence of ZnSe/ZnS:Mn/ZnS Quantum Dots for Detecting E. Coli and MRSA Bacteria Quickly

In this study, we used a starch paste stabilizer to synthesize ZnSe: Mn/ZnS- Starch and ZnSe/ZnS: Mn/ZnS-starch quantum dot (QDs) in a non-toxic aqueous solvent. The -CH2-OH group of the starch paste promotes dispersibility and improves the compatibility of quantum dots with antibodies, its bonding is observed in the FTIR spectrum. Besides, the Mn-doped ZnS buffer shell with various concentrations (1, 3, 5, 7, and 9%) influence structure, optical, and photoluminescence of QDs properties were investigated in detail. The greatest luminescence intensity is achieved at a molar ratio of 3% Mn2+/Zn2+. Moreover, the ZnS: Mn buffer shell helps to enhance the fluorescence intensity and quantum yield (QY) of the ZnSe/ZnS: Mn/ZnS QDs, which are higher than ZnSe: Mn/ZnS-starch QDs. Through protein A and EDC bridging, ZnSe/ZnS:3%Mn/ZnS- Starch resulted in good signal and sensitivity, with no toxicity to E. coli O157:H7 and MRSA strains.

BODIPY-labelled acetylcholinesterase reactivators can be encapsulated into ferritin nanovehicles for enhanced bioavailability in the CNS

The BODIPY-labelled oxime reactivator was prepared and used to study its biodistribution into central nervous system. The newly synthesized oxime was found to be weak inhibitor of acetylcholinesterase and strong inhibitor of butyrylcholinesterase. Its reactivation ability for organophosphate inhibited acetylcholinesterase was found similar to a parent oxime. The BODIPY-labelled oxime was further encapsulated into recombinant human H-ferritin and evaluated in vitro and in vivo. The oxime or encapsulated oxime were found to be bioaccumulated primarily in liver and kidneys of mice, but some amount was distributed also to the brain, where it was detectable even after 24 h. The BODIPY-labelled oxime encapsulated to human H-ferritin showed better CNS bioaccumulation and tissue retention at 8 and 24 h time points compared to free oxime, although the fluorescence results might be biased due to BODIPY metabolites identified in tissue homogenates. Taken together, the study demonstrates the first utilization of recombinant ferritins for changing the unfavourable pharmacokinetics of oxime reactivators and brings promising results for follow-up studies.

Strategies for enhanced bioavailability of oxime reactivators in the central nervous system

Oxime reactivators of acetylcholinesterase are commonly used to treat highly toxic organophosphate poisoning. They are effective nucleophiles that can restore the catalytic activity of acetylcholinesterase; however, their main limitation is the difficulty in crossing the blood-brain barrier (BBB) because of their strongly hydrophilic nature. Various approaches to overcome this limitation and enhance the bioavailability of oxime reactivators in the CNS have been evaluated; these include structural modifications, conjugation with molecules that have transporters in the BBB, bypassing the BBB through intranasal delivery, and inhibition of BBB efflux transporters. A promising approach is the use of nanoparticles (NPs) as the delivery systems. Studies using mesoporous silica nanomaterials, poly (L-lysine)-graft-poly(ethylene oxide) NPs, metallic organic frameworks, poly(lactic-co-glycolic acid) NPs, human serum albumin NPs, liposomes, solid lipid NPs, and cucurbiturils, have shown promising results. Some NPs are considered as nanoreactors for organophosphate detoxification; these combine bioscavengers with encapsulated oximes. This study provides an overview and critical discussion of the strategies used to enhance the bioavailability of oxime reactivators in the central nervous system.

Boosted Chemical Protective Properties Using Interface Constructed between Ti3C2Tx MXene and Natural Rubber

Rubbers are extensively applied in chemical protective clothing (CPC) due to their eye-catching anti-penetration of chemicals. However, their impermeability, particularly that of natural rubber (NR), is unsatisfactory. In this work, we demonstrate the facile construction of Ti3C2Tx MXene/NR interface using a plant-scale and feasible method combining latex mixing, emulsion flocculation, and flat-plate vulcanisation. The above crafts achieved a homogeneous dispersion of Ti3C2Tx MXene in the NR matrix in a single layer, thereby constructing a strong interfacial interaction between Ti3C2Tx MXene and NR, which induced the formation of a robust three-dimensional (3D) network in the composite. The anti-swelling capacity of the 3D cross-linked network structure and the layered structure of Ti3C2Tx MXene effectively prolonged the permeation path of toxic chemicals. Compared with pure NR, the nanocomposite with 1 wt% of Ti3C2Tx MXene showed substantially enhanced breakthrough times of toluene, dichloromethane, and concentrated sulfuric acid (increased by 140%, 178.6%, and 92.5%, respectively). Furthermore, its tensile strength, elongation at break, and shore hardness increased by 7.847 MPa, 194%, and 12 HA, respectively. Taken together with the satisfactory anti-permeability, tensile strength, elongation at break, and shore hardness, the resulting Ti3C2Tx MXene/NR nanocomposites hold promise for application to long-term and high-strength CPC in the chemical industry and military fields.

Metal-Organic Framework Gels for Adsorption and Catalytic Detoxification of Chemical Warfare Agents: A Review

Chemical warfare agents (CWAs) have brought great threats to human life and social stability, and it is critical to investigate protective materials. MOF (metal-organic framework) gels are a class with an extended MOF architecture that are mainly formed using metal-ligand coordination as an effective force to drive gelation, and these gels combine the unique characteristics of MOFs and organic gel materials. They have the advantages of a hierarchically porous structure, a large specific surface area, machinable block structures and rich metal active sites, which inherently meet the requirements for adsorption and catalytic detoxification of CWAs. A series of advances have been made in the adsorption and catalytic detoxification of MOF gels as chemical warfare agents; however, overall, they are still in their infancy. This review briefly introduces the latest advances in MOF gels, including pure MOF gels and MOF composite gels, and discusses the application of MOF gels in the adsorption and catalytic detoxification of CWAs. Meanwhile, the influence of microstructures (pore structures, metal active site, etc.) on the detoxification performance of protective materials is also discussed, which is of great significance in the exploration of high-efficiency protective materials. Finally, the review looks ahead to next priorities. Hopefully, this review can inspire more and more researchers to enrich the performance of MOF gels for applications in chemical protection and other purification and detoxification processes.

Novel uncharged triazole salicylaldoxime derivatives as potential acetylcholinesterase reactivators: comprehensive computational study, synthesis and in vitro evaluation

The present study aims to design and synthesise novel uncharged aldoximes and explore their reactivation abilities, structures, descriptors, and mechanisms of action, as well as assessing the interactions and stabilities in the active site of paraoxon-inhibited acetylcholinesterase enzyme using computational studies and in vitro assay. The comprehensive computational studies including quantum chemical, molecular dynamics simulations and molecular docking were conducted on paraoxon-inhibited human acetylcholinesterase to investigate the reactivation ability of the novel aldoximes and compare them with pralidoxime as a reactivator model molecule.

Combination of acetylcholinesterase inhibitors and NMDA receptor antagonists increases survival rate in soman-poisoned mice

Organophosphorus nerve agents pose a global threat to both military personnel and civilian population, because of their high acute toxicity and insufficient medical countermeasures. Commonly used drugs could ameliorate the intoxication and overall medical outcomes. In this study, we tested the drugs able to alleviate the symptoms of Alzheimer's disease (donepezil, huperzine A, memantine) or Parkinson's disease (procyclidine). They were administered to mice before soman intoxication in terms of their: i) protection potential against soman toxicity and ii) influence on post-exposure therapy consisting of atropine and asoxime (also known as oxime HI-6). Their pretreatment effect was not significant, when administered alone, but in combination (acetylcholinesterase inhibitor such as denepezil or huperzine A with NMDA antagonist such as memantine or procyclidine) they lowered the soman toxicity more than twice. These combinations also positively influenced the efficacy of post-exposure treatment in a similar fashion; the combinations increased the therapeutic effectiveness of antidotal treatment. In conclusion, the most effective combination - huperzine A and procyclidine - lowered the toxicity three times and improved the post-exposure therapy efficacy more than six times. These results are unprecedented in the published literature.

Development of a carbon quantum dot-based sensor for the detection of acetylcholinesterase and the organophosphate pesticide

In this study, a proper and reliable fluorometric method is introduced for screening acetylcholinesterase (AChE) and its inhibitors, using carbon quantum dots (CQDs) as the signal reporter. Pure, S-doped, and P-doped CQDs, were synthesized and their recoverable fluorescence quenching properties were observed, when exposed to Hg2+, Cu2+, and Fe3+ quenching ions, respectively. The study on the recovery of their emission showed that after the introduction of another guest substance with a stronger affinity to the quenching ions, their fluorescence is restored. The Design Expert software was employed to compare the performance of the three CQDs, as fluorescent probes, based on their quenching efficiency and the percentage of their emission recovery in the presence of AChE and acetylthiocholine (ATCh). Based on the statistical analysis, among the studied CQDs, S-doped CQD was the most suitable candidate for sensor designing. The detection mechanism for the proposed S-doped CQD-based sensor is as follows: The strong binding of Cu2+ ions to carboxyl groups of S-doped CQD quenches the fluorescence signal. Then, hydrolysis of ATCh into thiocholine (TCh) in the presence of AChE causes fluorescence recovery, due to the stronger affinity of Cu2+ to the TCh, rather than the CQD. Finally, in the presence of malathion and chlorpyrifos inhibitors, AChE loses its ability to hydrolyze ATCh to TCh, so the fluorescence emission remains quenched. Based on the proposed detection technique, the designed sensor showed detection limits of 1.70 ppb and 1.50 ppb for malathion and chlorpyrifos, respectively.

Antidotes in Clinical Toxicology-Critical Review

Poisoning and overdose are very important aspects in medicine and toxicology. Chemical weapons pose a threat to civilians, and emergency medicine principles must be followed when dealing with patients who have been poisoned or overdosed. Antidotes have been used for centuries and modern research has led to the development of new antidotes that can accelerate the elimination of toxins from the body. Although some antidotes have become less relevant due to modern intensive care techniques, they can still save lives or reduce the severity of toxicity. The availability of antidotes is crucial, especially in developing countries where intensive care facilities may be limited. This article aims to provide information on specific antidotes, their recommended uses, and potential risks and new uses. In the case of poisoning, supportive therapies are most often used; however, in many cases, the administration of an appropriate antidote saves the patient's life. In this review, we reviewed the literature on selected antidotes used in the treatment of poisonings. We also characterised the antidotes (bio)chemically. We described the cases in which they are used together with the dosage recommendations. We also analysed the mechanisms of action. In addition, we described alternative methods of using a given substance as a drug, an example of which is N-acetylcysteine, which can be used in the treatment of COVID-19. This article was written as part of the implementation of the project of the Polish Ministry of Education and Science, "Toxicovigilance, poisoning prevention, and first aid in poisoning with xenobiotics of current clinical importance in Poland", grant number SKN/SP/570184/2023.

Chemical, Physical, and Toxicological Properties of V-Agents

V-agents are exceedingly toxic organophosphate nerve agents. The most widely known V-agents are the phosphonylated thiocholines VX and VR. Nonetheless, other V-subclasses have been synthesized. Here, a holistic overview of V-agents is provided, where these compounds have been categorized based on their structures to facilitate their study. A total of seven subclasses of V-agents have been identified, including phospho(n/r)ylated selenocholines and non-sulfur-containing agents, such as VP and EA-1576 (EA: Edgewood Arsenal). Certain V-agents have been designed through the conversion of phosphorylated pesticides to their respective phosphonylated analogs, such as EA-1576 derived from mevinphos. Further, this review provides a description of their production, physical properties, toxicity, and stability during storage. Importantly, V-agents constitute a percutaneous hazard, while their high stability ensures the contamination of the exposed area for weeks. The danger of V-agents was highlighted in the 1968 VX accident in Utah. Until now, VX has been used in limited cases of terrorist attacks and assassinations, but there is an increased concern about potential terrorist production and use. For this reason, studying the chemistry of VX and other less-studied V-agents is important to understand their properties and develop potential countermeasures.

A PET and ESIPT-communicated ratiometric, turn-on chromo-fluorogenic sensor for rapid and sensitive detection of sarin gas mimic, diethylchlorophosphate

Fast and precise identification of toxic G-series nerve agents in the solution and vapor phase is urgently needed to save human beings from unwanted wars and terrorist attacks, which is challenging to execute practically. In this article, we have designed and synthesized a sensitive and selective phthalimide-based chromo-fluorogenic sensor, DHAI, by a simple condensation process that shows ratiometric and turns on chromo-fluorogenic behavior towards Sarin gas mimic diethylchlorophosphate (DCP) in liquid and vapor phases, respectively. A colorimetric change, from yellow to colorless, is observed in the DHAI solution due to the introduction of DCP in daylight. A remarkable cyan color photoluminescence enhancement is noticed in the presence of DCP in the DHAI solution, which is observable to the naked under a portable 365 nm UV lamp. The mechanistic aspects of the detection of DCP by employing DHAI have been revealed by time-resolved photoluminescence decay analysis and ¹H NMR titration investigation. Our probe DHAI exhibits linear photoluminescence enhancement from 0 to 500 μM with a detection limit of nanomolar range from non-aqueous to semi-aqueous media. For practical utility, a DHAI-stained test kit employing Whatman-41 filter paper has been fabricated and used as a portable and displayable photonic device for on-site detection of Sarin gas surrogate, DCP. Also, a dip-stick experiment has been demonstrated to identify the vapor of Sarin gas mimics DCP colorimetrically and fluorometrically. The concentrations of DCP in various water samples have been evaluated with the help of a standard fluorescence curve for real sample analysis.

MOF-Polymer Mixed Matrix Membranes as Chemical Protective Layers for Solid-Phase Detoxification of Toxic Organophosphates

Zirconium-based metal-organic frameworks (Zr-MOFs) have been demonstrated as potent catalysts for the hydrolytic detoxification of organophosphorus nerve agents and their simulants. However, the practical implementation of these Zr-MOFs is limited by the poor processability of their powdered form and the necessity of water media buffered by a volatile liquid base in the catalytic reaction. Herein, we demonstrate the efficient solid-state hydrolysis of a nerve agent simulant (dimethyl-4-nitrophenyl phosphate, DMNP) catalyzed by Zr-MOF-based mixed matrix membranes. The mixed matrix membranes were fabricated by incorporating MOF-808 into the blending matrix of poly(vinylidene fluoride) (PVDF), poly(vinylpyrrolidone) (PVP), and imidazole (Im), in which MOF-808 provides highly active catalytic sites, the hydrophilic PVP helps to retain water for promoting the hydrolytic reaction, and Im serves as a base for catalytic site regeneration. Impressively, the mixed matrix membranes displayed excellent catalytic performance for the solid-state hydrolysis of DMNP under high humidity, representing a significant step toward the practical application of Zr-MOFs in chemical protective layers against nerve agents.

Dual-Function Detoxifying Nanofabrics against Nerve Agent and Blistering Agent Simulants

The development of functional materials that can detoxify multiple chemical warfare agents (CWAs) at the same time is of great significance to cope with the uncertainty of CWA use in real-world situations. Although many catalysts capable of detoxifying CWAs have been reported, there is still a lack of effective means to integrate these catalytic-active materials on practical fibers/fabrics to achieve effective protection against coexistence of a variety of CWAs. In this work, by a combination of electrospinning and in situ solvothermal reaction, PAN@Zr(OH)₄@MOF-808 nanofiber membranes were prepared for detoxification of both nerve agent and blistering agent simulants dimethyl 4-nitrophenyl phosphate (DMNP) and 2-chloroethyl ethyl sulfide (CEES). Under the catalytic effect of the MOF-808 component, DMNP hydrolysis with a half-life as short as 1.19 min was achieved. Meanwhile, an 89.3% CEES removal rate was obtained within 12 h by adsorption and catalysis of MOF-808 and Zr(OH)₄ components at ambient conditions, respectively. PAN@Zr(OH)₄@MOF-808 nanofiber membranes also showed a superior blocking effect on CEES compared to bare PAN and PAN@Zr(OH)₄ nanofiber membranes. Simultaneous protection against DMNP and CEES showed effective inhibition of both simulants for at least 2 h. The preparation method also imparted intrinsically good interfacial adhesion between the components, contributing to the excellent recycling stability of PAN@Zr(OH)₄@MOF-808 nanofiber membranes. Therefore, the prepared composite nanofabrics have great application potential, which provides a new idea for the construction of broad-spectrum protective detoxification materials.

What do we currently know about Novichoks? The state of the art

Novichok is the name given to the group of nerve agents created stealthily in the later phases of the Cold War by the Soviet Union. Constitute the fourth generation of chemical warfare agents; like other nerve agents, they are organophosphorus compounds designed to be incurable and undetectable. The mechanism of action is based on the non-competitive and irreversible inhibition of acetylcholinesterase. Due to their enormous toxicity, Novichoks have become attractive targets for terrorists. However, little information is known about the identity of nerve agents. Furthermore, these compounds have never been submitted to the Chemical Weapons Convention. Our article aspires to provide a general overview of Novichoks knowledge. As part of this, we reviewed the available literature data to answer the question, what are Novichoks? In addition to the physical and chemical properties of A-agents, synthesis, mechanism of action, and toxicity of nerve agents were also reviewed. We hope that this review will highlight the tremendous threat posed by nerve agents and will inspire further studies on the interdisciplinary aspects of these compounds.

Therapy of Organophosphate Poisoning via Intranasal Administration of 2-PAM-Loaded Chitosomes

Chitosan-decorated liposomes were proposed for the first time for the intranasal delivery of acetylcholinesterase (AChE) reactivator pralidoxime chloride (2-PAM) to the brain as a therapy for organophosphorus compounds (OPs) poisoning. Firstly, the chitosome composition based on phospholipids, cholesterol, chitosans (Cs) of different molecular weights, and its arginine derivative was developed and optimized. The use of the polymer modification led to an increase in the encapsulation efficiency toward rhodamine B (RhB; ~85%) and 2-PAM (~60%) by 20% compared to conventional liposomes. The formation of monodispersed and stable nanosized particles with a hydrodynamic diameter of up to 130 nm was shown using dynamic light scattering. The addition of the polymers recharged the liposome surface (from -15 mV to +20 mV), which demonstrates the successful deposition of Cs on the vesicles. In vitro spectrophotometric analysis showed a slow release of substrates (RhB and 2-PAM) from the nanocontainers, while the concentration and Cs type did not significantly affect the chitosome permeability. Flow cytometry and fluorescence microscopy qualitatively and quantitatively demonstrated the penetration of the developed chitosomes into normal Chang liver and M-HeLa cervical cancer cells. At the final stage, the ability of the formulated 2-PAM to reactivate brain AChE was assessed in a model of paraoxon-induced poisoning in an in vivo test. Intranasal administration of 2-PAM-containing chitosomes allows it to reach the degree of enzyme reactivation up to 35 ± 4%.

Transdermal Delivery of 2-PAM as a Tool to Increase the Effectiveness of Traditional Treatment of Organophosphate Poisoning

For the first time, the efficacy of post-exposure treatment of organophosphate (OP) poisoning was increased by transdermal delivery of acetylcholinesterase (AChE) reactivator pyridine-2-aldoxime methochloride (2-PAM) as a preventive countermeasure. By selecting the optimal ratio of components, classical transfersomes (based on soybean phosphatidylcholine and Tween 20) and modified transfersomes (based on soybean phosphatidylcholine, Tween 20 and pyrrolidinium cationic surfactants with different hydrocarbon tail lengths) were obtained for 2-PAM encapsulation. Transfersomes modified with tetradecylpyrrolidinium bromide showed the best results in encapsulation efficiency and sustained release of 2-PAM from vesicles. Using Franz cells, it was found that the incorporation of surfactants into PC liposomes results in a more prolonged release of 2-PAM through the rat skin. Transfersomes containing 2-PAM, after exhaustive physical and chemical characterization, were embedded in a gel based on Carbopol^® 940. A significantly high degree of erythrocyte AChE reactivation (23 ± 7%) was shown for 2-PAM in unmodified transfersomes in vivo. Preliminary transdermal administration of 2-PAM 24 h before emergency post-exposure treatment of OP poisoning leads to an increase in the survival rate of rats from 55% to 90%.

A rapid in vitro assay for evaluating the effects of acetylcholinesterase inhibitors and reactivators in the rat basolateral amygdala

We established a novel brain slice assay to test the ability of acetylcholinesterase (AChE) reactivators to prevent ACh-induced M1 muscarinic acetylcholine receptor (mAChR) dependent hyperexcitability observed after exposure to the organophosphate (OP)-based AChE inhibitor and sarin surrogate 4-nitrophenyl isopropyl methylphosphonate (NIMP). Whole-cell patch clamp recordings were used to evaluate the response of pyramidal neurons in the rat basolateral amygdala (BLA) to brief (1 min) bath application of ACh (100 μM), either in control conditions, or after exposure to NIMP ± an AChE reactivator. Bath application of ACh produced atropine- and pirenzepine-sensitive inward currents in voltage clamped BLA pyramidal neurons, and increased the frequency of spontaneous EPSCs, suggesting robust activation of M1 mAChRs. Responses to ACh were increased ~3–5 fold in slices that had been preincubated in NIMP, and these effects were reversed in a concentration dependent manner by exposure to a commercially available AChE reactivator. The current work outlines a simple assay that can be used to evaluate the efficacy of both known and novel AChE reactivators in an area of the limbic system that likely contributes to seizures after acute exposure to OP-based AChE inhibitors.

Visible-Light-Initiated Multicomponent Reactions of α-Diazoesters to Access Organophosphorus Compounds

A simple visible-light-initiated strategy has been established for the construction of organophosphorus compounds via aerobic multicomponent reaction of α-diazoesters, cyclic ethers, and P(O)H compounds under air. A number of phosphonates and phosphinates could be efficiently isolated in moderate to good yields without the use of photosensitizers and metal reagents. This multicomponent reaction has advantages of mild condition, simple operation, eco-friendly energy, good functional-group tolerance, and gram-scale synthesis.

Controllable synthesis of conjugated microporous polymer films for ultrasensitive detection of chemical warfare agents

Nerve agents, one of the most toxic chemical warfare agents, seriously threaten human life and public security. The high toxicity of nerve agents makes the development of fluorescence sensors with suitable limit of detection challenging. Here, we propose a sensor design based on a conjugated microporous polymer film for the detection of diethyl chlorophosphate, a substitute of Sarin, with low detection limit of 2.5 ppt. This is due to the synergy of the susceptible on-off effect of hybridization and de-hybridization of hybrid local and charge transfer (HLCT) materials and the microporous structure of CMP films facilitating the inward diffusion of DCP vapors, and the extended π-conjugated structure. This strategy provides a new idea for the future development of gas sensors. In addition, a portable sensor is successfully integrated based on TCzP-CMP films that enables wireless, remote, ultrasensitive, and real-time detection of DCP vapors.

Antiseizure and Neuroprotective Efficacy of Midazolam in Comparison with Tezampanel (LY293558) against Soman-Induced Status Epilepticus

Acute exposure to nerve agents induces status epilepticus (SE), which can cause death or long-term brain damage. Diazepam is approved by the FDA for the treatment of nerve agent-induced SE, and midazolam (MDZ) is currently under consideration to replace diazepam. However, animal studies have raised questions about the neuroprotective efficacy of benzodiazepines. Here, we compared the antiseizure and neuroprotective efficacy of MDZ (5 mg/kg) with that of tezampanel (LY293558; 10 mg/kg), an AMPA/GluK1 receptor antagonist, administered 1 h after injection of the nerve agent, soman (1.2 × LD50), in adult male rats. Both of the anticonvulsants promptly stopped SE, with MDZ having a more rapid effect. However, SE reoccurred to a greater extent in the MDZ-treated group, resulting in a significantly longer total duration of SE within 24 h post-exposure compared with the LY293558-treated group. The neuroprotective efficacy of the two drugs was studied in the basolateral amygdala, 30 days post-exposure. Significant neuronal and inter-neuronal loss, reduced ratio of interneurons to the total number of neurons, and reduction in spontaneous inhibitory postsynaptic currents accompanied by increased anxiety were found in the MDZ-treated group. The rats treated with LY293558 did not differ from the control rats (not exposed to soman) in any of these measurements. Thus, LY293558 has significantly greater efficacy than midazolam in protecting against prolonged seizures and brain damage caused by acute nerve agent exposure.

An efficient multi-enzyme cascade platform based on mesoporous metal-organic frameworks for the detection of organophosphorus and glucose

An efficient colorimetric detection platform based on multi-enzyme cascade has been developed for detection of organophosphorus. Firstly, the dual-enzyme platform was prepared and applied for sensitive glucose detection (detection limit 0.32 μM). And then three enzymes, including acetylcholinesterase, horseradish peroxidase and choline oxidase were encapsulated in cruciate flower-like zeolitic imidazolate framework-8 (CF-ZIF-8) through one-step co-precipitation to construct detection platform with acetylcholine chloride as substrate. The acephate inhibited the activity of acetylcholinesterase, obstructed the cascade reaction and reduced the production of H₂O₂, resulting in the changes of color intensity for the colorimetric detection. With suitable size and porous structure, CF-ZIF-8 provided a good microenvironment for guaranteeing the activity and spatial proximity of enzymes. The multi-enzyme platform displayed great performances with the detection limit of 0.23 nM for acephate. It was applied to the detection of acephate in Chinese cabbage and romaine, verifying the practicability of this platform.

Zirconium Metal-Organic Polyhedra with Dual Behavior for Organophosphate Poisoning Treatment

Organophosphate nerve agents and pesticides are extremely toxic compounds because they result in acetylcholinesterase (AChE) inhibition and concomitant nerve system damage. Herein, we report the synthesis, structural characterization, and proof-of-concept utility of zirconium metal-organic polyhedra (Zr-MOPs) for organophosphate poisoning treatment. The results show the formation of robust tetrahedral cages [((n-butylCpZr)3(OH)3O)4L6]Cl6 (Zr-MOP-1; L = benzene-1,4-dicarboxylate, n-butylCp = n-butylcyclopentadienyl, Zr-MOP-10, and L = 4,4'-biphenyldicarboxylate) decorated with lipophilic alkyl residues and possessing accessible cavities of ∼9.8 and ∼10.7 Å inner diameters, respectively. These systems are able to both capture the organophosphate model compound diisopropylfluorophosphate (DIFP) and host and release the AChE reactivator drug pralidoxime (2-PAM). The resulting 2-PAM@Zr-MOP-1(0) host-guest assemblies feature a sustained delivery of 2-PAM under simulated biological conditions, with a concomitant reactivation of DIFP-inhibited AChE. Finally, 2-PAM@Zr-MOP systems have been incorporated into biocompatible phosphatidylcholine liposomes with the resulting assemblies being non-neurotoxic, as proven using neuroblastoma cell viability assays.

Pharmacokinetics of three novel pyridinium aldoxime acetylcholinesterase reactivators in female rats

A platform of novel lipophilic substituted phenoxyalkyl pyridinium oximes was invented to reactivate organophosphate-inhibited acetylcholinesterase. This platform has provided superior efficacy in rats to the current standard of care, 2-PAM, for survival of lethal doses of nerve agent surrogates as well as evidence of brain penetration and neuroprotection. The pharmacokinetics of three of these novel oximes in female rats was studied for comparison to previous data in male rats. Compared to the published half-life of 2-PAM (less than 2 h), the lead novel oxime, Oxime 20, displayed a plasma half-life of about 5 h in both sexes of rats following intramuscular administration. Very few sex differences in pharmacokinetic parameters were apparent. Oxime 20 displayed an increase in brain concentration to plasma concentration over the initial 2 h following intramuscular administration in male rats, with a plateau at 1 h; there were no differences in brain concentrations between the sexes at 2 h. Hepatic metabolism of Oxime 20 was higher in rat microsomes than in human microsomes. The relatively long plasma half-life is likely an important factor in both the enhanced survival and the neuroprotection previously observed for Oxime 20. The metabolism data suggest that the clearance of Oxime 20 could be slower in humans than was observed in rats, which might allow less frequent administration than 2-PAM for therapy of organophosphate acute toxicity. Therefore, the pharmacokinetic data combined with our earlier efficacy data suggest that Oxime 20 has potential as a superior therapeutic for nerve agent poisoning.

Copper-Catalyzed Phosphorylation of N,N-Disubstituted Hydrazines: Synthesis of Multisubstituted Phosphorylhydrazides as Potential Anticancer Agents

An efficient copper-catalyzed aerobic oxidative cross-dehydrogenative coupling reaction for the synthesis of multisubstituted phosphorylhydrazides from N,N-disubstituted hydrazines and hydrogen phosphoryl compounds is accomplished. The reaction proceeds under mild conditions without the addition of any external oxidants and bases. This work reported here represents a direct P(═O)-N-N bond formation with the advantages of being operationally simple, good functional group tolerance, and high atom and step economy. Furthermore, the selected compounds exhibit potential inhibitory activity against tumor cells, which can be used in the field of screening of anticancer agents as new chemical entities.

A New Class of Bi- and Trifunctional Sugar Oximes as Antidotes against Organophosphorus Poisoning

Recent events demonstrated that organophosphorus nerve agents are a serious threat for civilian and military populations. The current therapy includes a pyridinium aldoxime reactivator to restore the enzymatic activity of acetylcholinesterase located in the central nervous system and neuro-muscular junctions. One major drawback of these charged acetylcholinesterase reactivators is their poor ability to cross the blood-brain barrier. In this study, we propose to evaluate glucoconjugated oximes devoid of permanent charge as potential central nervous system reactivators. We determined their in vitro reactivation efficacy on inhibited human acetylcholinesterase, the crystal structure of two compounds in complex with the enzyme, their protective index on intoxicated mice, and their pharmacokinetics. We then evaluated their endothelial permeability coefficients with a human in vitro model. This study shed light on the structural restrains of new sugar oximes designed to reach the central nervous system through the glucose transporter located at the blood-brain barrier.

Charged pyridinium oximes with thiocarboxamide moiety are equally or less effective reactivators of organophosphate-inhibited cholinesterases compared to analogous carboxamides

The organophosphorus antidotes, so-called oximes, are able to restore the enzymatic function of acetylcholinesterase (AChE) or butyrylcholinesterase (BChE) via cleavage of organophosphate from the active site of the phosphylated enzyme. In this work, the charged pyridinium oximes containing thiocarboxamide moiety were designed, prepared and tested. Their stability and pK_a properties were found to be analogous to parent carboxamides (K027, K048 and K203). The inhibitory ability of thiocarboxamides was found in low µM levels for AChE and high µM levels for BChE. Their reactivation properties were screened on human recombinant AChE and BChE inhibited by nerve agent surrogates and paraoxon. One thiocarboxamide was able to effectively restore function of NEMP- and NEDPA-AChE, whereas two thiocarboxamides were able to reactivate BChE inhibited by all tested organophosphates. These results were confirmed by reactivation kinetics, where thiocarboxamides were proved to be effective, but less potent reactivators if compared to carboxamides.

Ultrathin graphdiyne nanosheets confining Cu quantum dots as robust electrocatalyst for biosensing featuring remarkably enhanced activity and stability

There is an urgent need for developing electrochemical biosensor based on the acetylcholinesterase (AChE) inhibition to real-time analysis of organophosphorus pesticides (OPs), but it is suffered from the sluggish electrode kinetics and high oxidation potential toward signal species. Herein, a nanocomposite of ultrafine Cu quantum dots (QD) uniformly loaded on three-dimensional ultrathin graphdiyne (GDY) nanosheets (denoted as Cu@GDY) was synthesized via a one-step strategy, which showing high-density of active sites with persistent stability. Then an AChE biosensor based on Cu@GDY was fabricated to detect OPs, and the results revealed that the Cu@GDY nanocomposite can significantly amplifies electrochemical signal and reduces the oxidation potential for OPs. The strong interaction between active site of Cu@GDY and thiocholine signal species caused rapid analyte aggregation and decreased the reaction activation energy of thiocholine electro-oxidation. Benefiting from the excellent catalytic activity of Cu@GDY nanocomposite and reasonable regulation of enzyme inhibition kinetics, the biosensor achieved rapid and sensitive detection of OPs with a detection limit of 1 μg L^-1 for paraoxon. Furthermore, the biosensor demonstrated great reproducibility, good stability and high recovery rate for OPs detection in real samples. Cu@GDY based sensor also displayed high catalytic activities and good selectivity to the non-enzymatic detection of glucose in alkaline medium. Cu@GDY offers a versatile and promising platform for sensors and biosensors featuring remarkably enhanced activity and stability, and can be applied to many other fields as desirable electrocatalyst.

Solid-state degradation and visual detection of the nerve agent GB by SA@UiO-66-NH2@PAMAM hydrogel

A new sodium alginate (SA) composite hydrogel for rapid solid-state degradation of organophosphorus derivatives and can be used to monitor hydrolysis of nerve agent GB.

Layer-by-Layer Integration of Zirconium Metal-Organic Frameworks onto Activated Carbon Spheres and Fabrics with Model Nerve Agent Detoxification Properties

We report the controlled synthesis of thin films of prototypical zirconium metal-organic frameworks [Zr₆O₄(OH)₄(benzene-1,4-dicarboxylate-2-X)₆] (X = H, UiO-66 and X = NH₂, UiO-66-NH₂) over the external surface of shaped carbonized substrates (spheres and textile fabrics) using a layer-by-layer method. The resulting composite materials contain metal-organic framework (MOF) crystals homogeneously distributed over the external surface of the porous shaped bodies, which are able to capture an organophosphate nerve agent simulant (diisopropylfluorophosphate, DIFP) in competition with moisture (very fast) and hydrolyze the P-F bond (slow). This behavior confers the composite material self-cleaning properties, which are useful for blocking secondary emission problems of classical protective equipment based on activated carbon.

Agile Detection of Chemical Warfare Agents by Machine Vision: a Supramolecular Approach

The supramolecular detection by image analysis of a simulant chemical warfare agent on a solid device containing a selective molecular sensor based on a BODIPY scaffold is reported. The recognition properties were investigated in solution, demonstrating high affinity (log K 6.60) and sensitivity (LOD 10 ppt). A test strip also confirmed the sensing properties in gas phase. Image analysis of the solid device allows quantitative information about the simulant to be obtained, recovering the sensor almost 5 times and thus confirming the goal of the supramolecular approach.

Caged Oxime Reactivators Designed for the Light Control of Acetylcholinesterase Reactivation†

Despite its promising role in the active control of biological functions by light, photocaging remains untested in acetylcholinesterase (AChE), a key enzyme in the cholinergic family. Here, we describe synthesis, photochemical properties and biochemical activities of two caged oxime compounds applied in the photocontrolled reactivation of the AChE inactivated by reactive organophosphate. Each of these consists of a photocleavable coumarin cage tethered to a known oxime reactivator for AChE that belongs in an either 2-(hydroxyimino)acetamide or pyridiniumaldoxime class. Of these, the first caged compound was able to successfully go through oxime uncaging upon irradiation at long-wavelength ultraviolet light (365 nm) or visible light (420 nm). It was further evaluated in AChE assays in vitro under variable light conditions to define its activity in the photocontrolled reactivation of paraoxon-inactivated AChE. This assay result showed its lack of activity in the dark but its induction of activity under light conditions only. In summary, this article reports a first class of light-activatable modulators for AChE and it offers assay methods and novel insights that help to achieve an effective design of caged compounds in the enzyme control.