Agents GB Research Articles

Efficacy of the oxime HI-6 dimethanesulphonate in the treatment of guinea-pigs exposed to the nerve agents GB and GD

The bispyridinium oxime HI-6 DMS is in development as an improved therapy for the treatment of patients exposed to organophosphorus nerve agents. The aim of the work described in this paper was to provide non-clinical data to support regulatory approval of HI-6 DMS, by demonstrating efficacy against an oxime-sensitive agent, GB and an oxime-resistant agent, GD. We investigated the dose-dependent protection afforded by therapy including atropine, avizafone and HI-6 DMS in guinea-pigs challenged with GB or GD. We also compared the efficacy of 30 mg.kg−1 of HI-6 DMS to an equimolar dose of the current in-service oxime P2S and the dichloride salt of HI-6 (HI-6 Cl2). In the treatment of GB or GD poisoning there was no significant difference between the salt forms. The most effective dose of HI-6 DMS in preventing lethality following challenge with GB was 100 mg.kg−1; though protection ratios of at least 25 were obtained at 10 mg.kg−1. Protection against GD was lower, and there was no significant increase in effectiveness of HI-6 DMS doses of 30 or 100 mg.kg−1. For GD, the outcome was improved by the addition of pyridostigmine pre-treatment. These data demonstrate the benefits of HI-6 DMS as a component of nerve agent therapy. © Crown copyright (2023), Dstl.

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.

Rhodamine phenol-based fluorescent probe for the visual detection of GB and its simulant DCP

Rhodamine phenol-based fluorescent probes have been synthesized. The probe RBNP demonstrates a rapid response and extreme low limit detection to diethylchlorophosphate and can rapidly and visually detect a real nerve agent GB in vapor.

Molecular Modeling Study of Uncharged Oximes Compared to HI-6 and 2-PAM Inside Human AChE Sarin and VX Conjugates.

The deleterious effects of nerve agents over the enzymes acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) turned these compounds into the most dangerous chemical weapons known. Among the antidotes in use today against these agents, oximes in combination with other drugs are the only treatment with any action. HI-6 and 2-PAM are cationic oximes proved to be effective for the reactivation of AChE inhibited by the nerve agents VX and sarin (GB). However, when it comes to reactivation of AChE inside the central or peripheral nervous systems, charged molecules present low diffusion due to low penetration through the blood–brain barrier. Uncharged oximes appear as an interesting alternative to solve this problem, but the development and enhancement of more efficient uncharged oximes capable of reactivating human AChE is still necessary. Given the limitations for in vivo and in vitro experimental studies with nerve agents, modeling is an important tool that can contribute to a better understanding of factors that may affect the efficiency of uncharged oximes. In order to investigate the interaction and behavior of cationic and uncharged oximes, we performed here molecular docking, molecular dynamics simulations, and binding energies calculations of the known cationic oximes HI-6 and 2-PAM plus four uncharged oximes found in the literature, complexed with human AChE (HssACHE) conjugated with the nerve agents VX and GB. The uncharged oximes showed different behaviors, especially RS194B, which presented stability inside AChE-VX, but presented free binding energy lower than cationic oximes, suggesting that structural alterations could favor its interactions with these complexes. In contrast, HI-6 and 2-PAM showed higher affinities with more negative binding energy values and larger contribution of the amino acid Asp74, demonstrating the importance of the quaternary nitrogen to the affinity and interaction of oximes with AChE-GB and AChE-VX conjugates.

Evaporation of the Nerve Agent GB From Common Matrices: A Model‐System Study

The measurement of a temperature‐dependent volatilization rate of the nerve agent GB (sarin) from various common matrices, using a laboratory‐designed wind tunnel (model system), is described. Small GB droplets are dispersed on the matrices surfaces, and samples are collected from the model system and analyzed utilizing a solid phase extraction/gas chromatography analytical method. Profiles demonstrating the vapor concentrations as a function of time are calculated. The results indicate that asphalt blocks relatively conserve GB, exhibiting a slow‐release mode of action over at least 2 weeks. Nevertheless, using standard decontamination procedures such as super tropical bleach may prevent this secondary evaporation risk. The concentration profile of commercial sidewalk bricks show a moderate decay, probably due to the existence of basic sites in the cement‐containing bricks. Fast clearance of GB is measured from smooth surface tiles, as these porous tiles both adsorb and/or degrade GB droplets very quickly.

Investigating the breakdown of the nerve agent simulant methyl paraoxon and chemical warfare agents GB and VX using nitrogen containing bases

A range of nitrogen containing bases was tested for the hydrolysis of a nerve agent simulant, methyl paraoxon (MP), and the chemical warfare agents, GB and VX. The product distribution was found to be highly dependant on the basicity of the base and the quantity of water used for the hydrolysis. This study is important in the design of decontamination technology, which often involve mimics of CWAs.

Synthesis and evaluation of a new phthalocyanine as sensor material for sarin detection

A new phthalocyanine material, 2,9,16,23-tetrakis [4-(hexafluoroisopropanol)-anilinomethyl]phthalocyaninato zinc (ZnPcF24N4O4) was designed and synthesized. The chemoselective material was coated on a 300MHz surface acoustic wave (SAW) device using cyclic voltammetry for the detection of sarin (GB) vapor. It was found that the observed frequency shifts were linear to the concentrations of sarin in the range of 0.6–43.4mg/m3 with a high sensitivity of 205.8Hz/mg/m3. The influences of other interfering vapors on the sensor response were also examined. The results showed that the phthalocyanine-based SAW sensor exhibited a fairly fast response, excellent reversibility, linearly sensitivity, and a high selectivity to vapor of the organophosphorus nerve agent GB.

Electroosmotic Water Vapor Transport across Novel, Smart, Functionalized Conducting Polymer Microporous Membranes in Active Mode at Very High Rates, with Concomitant Chemical Warfare (CW) Agent Blocking

Electroosmotic water vapor transport (WVT) across very thin, flexible, functionalized conducting polymer (CP) microporous (μP) membranes at a very high rate is reported. Both passive and active (6 VDC applied) WVT are reported, the latter for the first time ever. WVT occurs with concomitant, effective blocking of chemical warfare (CW) agents, again demonstrated for the first time ever. Initial active liquid||membrane||liquid interface studies demonstrated WVT rates of >1.7 × 10-5g .mm-2s-1, >3 × the highest prior reported values of 5 × 10-6g.mm-2s-1. Subsequent vapor||membrane|| vapor interface studies using industry-standard methods (including ASTM E96B Upright Cup (“WVT”), ASTM F2298 (“Dynamic Moisture Permeation Cell”) and ASTM F1868 (“Sweating Guard Hotplate”) were done at independent, external labs for independent corroboration. These yielded, e.g., WVT values of2564.4 g.m2.d-1 (passive) and3706.7 g.m2d-1 (active), to be compared with the highest (passive) value ever reported previously,984.8 g.m2.d-1 for a μP-Nylon membrane. More than 15 different membrane configurations, porosities and types were studied, including membranes with CP + organophosphate hydrolase (OPH), an enzyme reactive to CW agents. Efficient blocking of the actual CW agents GB, HD, VX is also reported, using the TOP-8-2-501standard. Membranes also passed all Industry-standard durability tests, e.g. ASTM D2261 (Tearing), ASTM D5034 (Breaking), ASTM D3886 (Abrasion), ASTM F392 (Gelbo Flex). Incorporation into smart soldiers’ garments was demonstrated; power consumption was -2. Mechanisms of enhanced WVT and CW agent blocking in the membranes are discussed.

The reactivity of quaternary ammonium- versus potassium- fluorides supported on metal oxides: paving the way to an instantaneous detoxification of chemical warfare agents

The reactions of the chemical warfare agents (CWAs) 2,2'-dichloroethyl sulfide (HD), O-ethyl S-2-(diisopropylamino)-ethyl methylphosphonothioate (VX) and isopropyl methylphosphonofluoridate (GB) with various metal oxide-supported quaternary ammonium fluorides (QAF) and/or potassium fluoride (KF) reagents are described. These active sorbents, which were prepared by a modified procedure, include alumina, silica and titania, enriched with "available" (not bound to the surface) fluoride ions. Alumina-based fluoride reagents were found to be more active than their silica or titania counterparts. QAF/Al(2)O(3) reagents, compared to KF/Al(2)O(3), exhibit an exceptional reactivity toward HD, as demonstrated both in reaction rates and product identity. For example, with TBAF, t(1/2) is 15 min for the formation of the elimination product divinyl sulfide (DVS), while with KF, t(1/2) is 10 h for the formation of the hydrolysis product thiodiglycol (TDG). On the other hand, both sorbents reacted similarly against the nerve agents GB or VX. In order to increase the "available" fluoride content on the solid surface, the mixed active sorbent TBAF/KF/Al(2)O(3) (20/20/60) was developed. On this powder, all three CWAs were degraded instantaneously at the low loading of 1 wt% (t(1/2) < 2 min) and rapidly at the higher loadings of 5-10 wt% (t(1/2) of minutes scale). We assume that the relatively large amount of inorganic fluoride (KF) acts synergistically as a reservoir for the more reactive organic fluorides (TBAF). Moreover, the alumina surface hydroxyl groups may also operate as a water reservoir for the hydrolysis of VX or GB. Therefore, TBAF/KF/Al(2)O(3) might be considered as a promising destructive sorbent for CWAs.

A murine model for sarin exposure using the carboxylesterase inhibitor CBDP

Sub-lethal exposure to sarin (GB), a potent chemical warfare agent, produces long-term neurological deficits in both humans and rodents. However, rodents express much higher levels of carboxylesterase (CaE) than humans and require a much higher dose of GB in rodents to produce neurotoxicity. In mice, the combination of the carboxylesterase inhibitor 2-(o-cresyl)-4H-1:3:2-benzodioxaphosphorin-2-oxide (CBDP) with the organophosphorus (OP) nerve agent GB renders mice more sensitive to OP poisoning. After the reduction in CaE, GB inhibits acetylcholinesterase at doses similar to those in human toxicity. A dose–response curve for GB was determined in male C57BL/6 mice after 1.5 mg/kg CBDP. A functional observational battery (FOB) for behavior was used to determine the dose needed to elicit seizure activity but maintain a mortality of less than 50%. Neuronal cell death was evaluated at 4, 7, 10 and 14 days post-GB exposure. Multiple brain areas were examined using cresyl violet: CA1 and the dentate gyrus of the hippocampus, amygdala and piriform cortex. GFAP staining was then measured as an index of cell death in the dentate gyrus of the hippocampus. The dentate gyrus and CA1 exhibited significant neuronal death indicated by both cresyl violet and GFAP staining. The treated animals also had a significant decrease in tissue and blood acetylcholinesterase, in addition to decreases in plasma CaE. CBDP renders mice more sensitive to the effects of GB exposure and mirrors a human symptomatic exposure dose.

Quantitation of Chemical Warfare Agents Using the Direct Analysis in Real Time (DART) Technique

Direct analysis in real time (DART) is an ion source that permits rapid mass spectrometric detection of gases, liquids, and solids in open air under ambient conditions. It is a unique technology in the field of chemical weapons detectors in that it does not require a vapor pressure, does not require sample preparation, and is nondestructive to the original sample. While the DART technique has had success as a first line instrument of detection, there have been lingering doubts over the technique's quantitative reliability and reproducibility. Here, we demonstrate its capability to produce linear calibration curves (R(2) = 0.99 or better) for the nerve agents GA, GB, and VX as well as the blister agent HD. Independently prepared check standards measured against these curves typically have recovery errors less than 3%. We show the DART instrument response to be linear over roughly 3 orders of magnitude. Furthermore, this study shows that averaging as few as three measurements for each data point is sufficient to produce high quality calibration curves, thus reducing data collection time and providing quicker results.

Reactions of Chemical Warfare Agent Simulants in the Common Ion Binary Ionic Liquid 1,2-Dimethyl-3-propylimidazolium/Copper(II) Bis(trifluoromethylsulfonyl)amide

Ionic liquids have the potential for being ideal alternatives for organic solvents in chemical warfare agent reactions and demilitarization processes. They are considered to be an excellent substitute, because of their extraordinarily wide liquid range, low melting points, chemical and thermal stability, high conductivity, and nonvolatility. In addition, many have excellent hydrophobic properties and immiscibility with water and offer the opportunity to isolate the chemical agents and reaction products from the environment. In this report, we describe a two-step process in which chemical warfare simulants are reacted with hydrogen peroxide (H2O2) followed by basic methanol in a common ion binary ionic liquid that consists of 1,2-dimethyl-3-propylimidazolium bis(trifluoromethylsulfonyl)amide and copper(II) bis(trifluoromethylsulfonyl)amide. The chemical agent simulants used in this study are diisopropylfluorophosphate, bis(2-ethylhexyl) phosphite, and 2-chloroethylphenyl sulfide, which simulate agents GB, ...

Aluminium sulfate and sodium aluminate buffer solutions for the destruction of phosphorus based chemical warfare agents

Nerve agents VX and GB (sarin) are sequestered and removed by aluminium sulfate and sodium aluminate mixtures adjusted to pH 4 in solution. The products of hydrolysis are removed with the alum floc below NMR detection limits over time depending and the amount of aluminium molar excess relative to agent. Half-lives for GB decomposition are 3.1 h and 1.1 h, respectively, for a 120 and a 1200 molar excess. For VX, the half-lives are 8.5 d and 2.9 d for a 240 and a 5000 molar aluminium excess. In the case of GB, fluorine is sequestered as the hexafluoroaluminate ion. In the case of VX, no phosphorus containing hydrolysis products including the very toxic S-[2-(diisopropyl-amino)-ethyl]methylphosphonothiolate (EA-2192) are detected in the hydrolysate.

Facile Hydrolysis-Based Chemical Destruction of the Warfare Agents VX, GB, and HD by Alumina-Supported Fluoride Reagents

A facile solvent-free hydrolysis (chemical destruction) of the warfare agents VX (O-ethyl S-2-(diisopropylamino)ethyl methylphosphonothioate), GB (O-isopropyl methylphosphonofluoridate or sarin), and HD (2,2'-dichloroethyl sulfide or sulfur mustard) upon reaction with various solid-supported fluoride reagents is described. These solid reagents include different alumina-based powders such as KF/Al(2)O(3), AgF/KF/Al(2)O(3), and KF/Al(2)O(3) enriched by so-called coordinatively unsaturated fluoride ions (termed by us as ECUF-KF/Al(2)O(3)). When adsorbed on these sorbents, the nerve agent VX quickly hydrolyzed (t(1/2) range between 0.1-6.3 h) to the corresponding nontoxic phosphonic acid EMPA as a major product (>90%) and to the relatively toxic desethyl-VX (<10%). The latter byproduct was further hydrolyzed to the nontoxic MPA product (t(1/2) range between 2.2-161 h). The reaction rates and the product distribution were found to be strongly dependent on the nature of the fluoride ions in the KF/Al(2)O(3) matrix and on its water content. All variations of the alumina-supported fluoride reagents studied caused an immediate hydrolysis of the highly toxic GB (t(1/2) < 10 min) to form the corresponding nontoxic phosphonic acid IMPA. A preliminary study of the detoxification of HD on these catalyst supports showed the formation of the nontoxic 1,4-thioxane as a major product together with minor amounts of TDG and vinylic compounds within a few days. The mechanisms and the efficiency of these processes were successfully studied by solid-state (31)P, (13)C, and (19)F MAS NMR.

Capacity of oximes to bind and reactivate nerve agent‐inhibited butyrylcholinesterase

Butyrylcholinesterase (BuChE) has promise as a stoichiometric prophylactic to protect against organophosphorus (OP) nerve agent poisoning. With an appropriate oxime, BuChE could be rapidly reactivated, making it quasi‐catalytic and enhance its protective efficacy. We examined the capacity of oximes known to be effective with acetylcholinesterase (2‐PAM, HI‐6, MMB‐4, TMB‐4, HS‐6, DAM and MINA) at different concentrations (10 mM – 10 μM) to reactivate BuChE inhibited by the nerve agents GA, GB, GF or VX. Only HI‐6 and HS‐6 were able to reactivate OP‐inhibited BuChE (GB and GF only) at a rate sufficiently fast to afford improved in vivo protective efficacy over enzyme alone. Thermodynamic parameters for the interaction of 2‐PAM and HI‐6 with BuChE were determined by isothermal titration calorimetry. Both interactions were found to have similar ΔG values (~ −5 kcal/mole). The binding of HI‐6 was exclusively enthalpically‐driven, while that of 2‐PAM had favorable entropic and enthalphic components. The results suggest that the tested oximes are inadequate to reactivate BuChE rapidly enough to make it an efficient quasi‐catalytic scavenger in vivo.This work was funded by DTRA.

Reactive desorption electrospray ionization for selective detection of the hydrolysis products of phosphonate esters

Reactive desorption electrospray ionization (reactive DESI) is demonstrated to be a rapid and sensitive method for the direct detection of alkyl methylphosphonic acids, the hydrolysis products and metabolites of the chemical warfare (CW) agents VX (S-2-diisopropylaminoethyl-O-ethyl methylphosphonothiolate) and GB (sarin, isopropylmethyl phosphonofluoridate). Rapid and sensitive detection of these compounds is readily achieved by performing DESI from a solid surface; detection specificity is enhanced by implementation of a heterogeneous ion/molecule reaction using boric acid in the spray solvent. The reagent ion H(2)BO(3) (-) generated in the spray readily reacts with condensed-phase alkyl MPA to form anionic adducts. The specificity of this chemical reaction, together with the characteristic fragmentation patterns of the reaction products, supplies a highly discriminatory detection method for methylphosphonic acid (MPA), ethylphosphonic acid (EMPA) and isopropyl methylphosphonic acid (IMPA) in complex matrices.

Detection of organophosphorous nerve agents using liquid crystals supported on chemically functionalized surfaces

Abstract We report use of thin films of the nematic liquid crystal E7 supported on chemically functionalized surfaces to indicate the presence of vapors of the organophosphorous nerve agents sarin (GB), soman (GD), tabun (GA) and VX. The surfaces were prepared by the deposition of metal perchlorate salts onto carboxylic acid-terminated self-assembled monolayers. When using surfaces prepared from aluminum perchlorate salts, the nematic film of E7 underwent a transition from a perpendicular orientation to a tilted or planar orientation upon exposure to vapors of GB, GD, GA or VX generated from a small drop of agent placed on a piece of filter paper. The orientational transition of the liquid crystal was readily apparent as an optical signal that was visible to the naked eye. The agent VX, which has the lowest vapor pressure of these organophosphorous nerve agents (∼140 ppb), was reported by the liquid crystal within 60 s. The agents GB, GD, and GA, which have higher vapor pressures, triggered responses in the liquid crystal that were evident within 15 s, 15 s, and 60 s, respectively. By preparing surfaces from perchlorate salts of aluminum(III), zinc(II) and iron(III) it was possible to distinguish between GB, VX and either GD or GA, thus demonstrating the feasibility of designing surfaces patterned with metal salts to detect and positively identify chemical warfare agents.

Development and Application of Acute Exposure Guideline Levels (AEGLs) for Chemical Warfare Nerve and Sulfur Mustard Agents

Acute exposure guideline levels (AEGLs) have been developed for the chemical warfare agents GB, GA, GD, GF, VX, and sulfur mustard. These AEGLs were approved by the National Advisory Committee for Acute Exposure Guideline Levels for Hazardous Substances after Federal Register publication and comment, and judged as scientifically valid by the National Research Council Committee on Toxicology Subcommittee on AEGLs. AEGLs represent general public exposure limits for durations ranging from 10 min to 8 h, and for three levels of severity (AEGL-1, AEGL-2, AEGL-3). Mild effects are possible at concentrations greater than AEGL-1, while life-threatening effects are expected at concentrations greater than AEGL-3. AEGLs can be applied to various civilian and national defense purposes, including evacuation and shelter-in-place protocols, reentry levels, protective clothing specifications, and analytical monitoring requirements. This report documents development and derivation of AEGL values for six key chemical warfare agents, and makes recommendations for their application to various potential exposure scenarios. This submission was sponsored by a contractor of the U.S. government under contract DE-AC05-00OR22725. Accordingly, the U.S. government retains a nonexclusive, royalty-free license to publish or reproduce these documents, or to allow others to do so, for U.S. government purposes. These documents may be freely distributed and used for noncommercial, scientific and educational purposes.

Direct Sampling of Chemical Weapons in Water by Photoionization Mass Spectrometry

The vulnerability of water supplies to toxic contamination calls for fast and effective means for screening water samples for multiple threats. We describe the use of photoionization (PI) mass spectrometry (MS) for high-speed, high-throughput screening and molecular identification of chemical weapons (CW) threats and other hazardous compounds. The screening technology can detect a wide range of compounds at subacute concentrations with no sample preparation and a sampling cycle time of approximately 45 s. The technology was tested with CW agents VX, GA, GB, GD, GF, HD, HN1, and HN3, in addition to riot agents and precursors. All are sensitively detected and give simple PI mass spectra dominated by the parent ion. The target application of the PI MS method is as a routine, real-time early warning system for CW agents and other hazardous compounds in air and in water. In this work, we also present comprehensive measurements for water analysis and report on the system detection limits, linearity, quantitation accuracy, and false positive (FP) and false negative rates for concentrations at subacute levels. The latter data are presented in the form of receiver operating characteristic curves of the form of detection probability P(D) versus FP probability P(FP). These measurements were made using the CW surrogate compounds, DMMP, DEMP, DEEP, and DIMP. Method detection limits (3sigma) obtained using a capillary injection method yielded 1, 6, 3, and 2 ng/mL, respectively. These results were obtained using 1-microL injections of water samples without any preparation, corresponding to mass detection limits of 1, 6, 3, and 2 pg, respectively. The linear range was about 3-4 decades and the dynamic range about 4-5 decades. The relative standard deviations were generally <10% at CW subacute concentrations levels.

Chemical warfare agent detection using MEMS-compatible microsensor arrays

Microsensors have been fabricated consisting of TiO/sub 2/ and SnO/sub 2/ sensing films prepared by chemical vapor deposition (CVD) on microelectromechanical systems array platforms. Response measurements from these devices to the chemical warfare (CW) agents GA (tabun), GB (sarin), and HD (sulfur mustard) at concentrations between 5 nmol/mol (ppb) and 200 ppb in dry air, as well as to CW agent simulants CEES (chloroethyl ethyl sulfide) and DFP (diisopropyl fluorophosphate) between 250 and 3000 ppb, are reported. The microsensors exhibit excellent signal-to-noise and reproducibility. The temperature of each sensor element is independently controlled by embedded microheaters that drive both the CVD process (375/spl deg/C) and sensor operation at elevated temperatures (325/spl deg/C-475/spl deg/C). The concentration-dependent analyte response magnitude is sensitive to conditions under which the sensing films are grown. Sensor stability studies confirm little signal degradation during 14 h of operation. Use of pulsed (200 ms) temperature-programmed sensing over a broad temperature range (20/spl deg/C-480/spl deg/C) enhances analyte selectivity, since the resulting signal trace patterns contain primarily kinetic information that is unique for each agent tested.