Dry Blood Spot sample collection for post-exposure monitoring of chemical warfare agents – In vivo determination of phosphonic acids using LC-MS/MS

Development of a molecularly imprinted polymer-based electrochemical sensor for the selective detection of nerve agent VX metabolite ethyl methylphosphonic acid in human plasma and urine samples

This study focuses on the detection of ethyl methyl phosphonic acid (EMPA), a metabolite of the banned organophosphorus nerve agent VX. We developed an electrochemical sensor utilizing the molecularly imprinted polymer (MIP) based on 4-aminobenzoic acid (4-ABA) and tetraethyl orthosilicate for the selective detection of EMPA in human plasma and urine samples. The 4-ABA@EMPA/MIP/GCE sensor was constructed by a thermal polymerization process on a glassy carbon electrode and sensor characterization was performed by cyclic voltammetry and electrochemical impedance spectroscopy. The 4-ABA@EMPA/MIP/GCE sensor demonstrated impressive linear ranges 1.0 × 10-10 M-2.5 × 10-9 M for the standard solution, 1.0 × 10-10 M-2.5 × 10-9 M for the urine sample, and 1.0 × 10-10 M-1 × 10-9 M of EMPA for the plasma sample with outstanding detection limits of 2.75 × 10-11 M (standard solution), 2.11 × 10-11 M (urine), and 2.36 × 10-11 M (plasma). The sensor exhibited excellent recovery percentages ranging from 99.86 to 101.30% in urine samples and 100.62 to 101.08% in plasma samples. These findings underscore the effectiveness of the 4-ABA@EMPA/MIP/GCE as a straightforward, highly sensitive, and selective interface capable of detecting the target analyte EMPA in human plasma and urine samples.

Monitoring Exposure to Five Chemical Warfare Agents Using the Dried Urine Spot Technique and Liquid Chromatography-Mass Spectrometry/Mass Spectrometry-In Vivo Determination of Sarin Metabolite in Mice

Dried urine spot (DUS) is a micro-sample collection technique, known for its advantages in handling, storage and shipping. It also uses only a small volume of urine, an essential consideration in working with small animals, or in acute medical situations. Alkyl-phosphonic acids are the direct and indicative metabolites of organophosphorus chemical warfare agents (OP-CWAs) and are present in blood and urine shortly after exposure. They are therefore crucially important for monitoring casualties in war and terror scenarios. We report here a new approach for the determination of the metabolites of five CWAs in urine using DUS. The method is based on a simple and rapid sample preparation, using only 50 µL of urine, spotted and dried on DBS paper, extracted using 300 µL methanol/water and analyzed via targeted LC-MS/MS. The detection limits for the five CWAs, sarin (GB), soman (GD), cyclosarin (GF), VX and RVX in human urine were from 0.5 to 5 ng/mL. Recoveries of (40-80%) were obtained in the range of 10-300 ng/mL, with a linear response (R2 > 0.964, R > 0.982). The method is highly stable, even with DUS samples stored up to 5 months at room temperature before analysis. It was implemented in a sarin in vivo exposure experiment on mice, applied for the time course determination of isopropyl methylphosphonic acid (IMPA, sarin hydrolysis product) in mice urine. IMPA was detectable even with samples drawn 60 h after the mice's (IN) exposure to 1 LD50 sarin. This method was also evaluated in a non-targeted screening for multiple potential CWA analogs (LC-Orbitrap HRMS analysis followed by automatic peak detection and library searches). The method developed here is applicable for rapid CWA casualty monitoring.

Detection of recombinant Spike protein in the blood of individuals vaccinated against SARS-CoV-2: Possible molecular mechanisms

PURPOSE

The SARS-CoV-2 pandemic prompted the development and use of next-generation vaccines. Among these, mRNA-based vaccines consist of injectable solutions of mRNA encoding for a recombinant Spike, which is distinguishable from the wild-type protein due to specific amino acid variations introduced to maintain the protein in a prefused state. This work presents a proteomic approach to reveal the presence of recombinant Spike protein in vaccinated subjects regardless of antibody titer.

EXPERIMENTAL DESIGN

Mass spectrometry examination of biological samples was used to detect the presence of specific fragments of recombinant Spike protein in subjects who received mRNA-based vaccines.

RESULTS

The specific PP-Spike fragment was found in 50% of the biological samples analyzed, and its presence was independent of the SARS-CoV-2 IgG antibody titer. The minimum and maximum time at which PP-Spike was detected after vaccination was 69 and 187 days, respectively.

CONCLUSIONS AND CLINICAL RELEVANCE

The presented method allows to evaluate the half-life of the Spike protein molecule "PP" and to consider the risks or benefits in continuing to administer additional booster doses of the SARS-CoV-2 mRNA vaccine. This approach is of valuable support to complement antibody level monitoring and represents the first proteomic detection of recombinant Spike in vaccinated subjects.

Toxic effects and bioaccumulation of pinacolyl methylphosphonate acid in zebrafish following soman exposure to a water environment

Soman has been shown to be highly neurotoxic and can be easily degraded to produce pinacolyl methylphosphonate acid (PMPA). Thus, the perniciousness of PMPA deserved serious attention after soman was exposed to the environment. However, the toxicity of PMPA was not clearly elucidated to date. In this regard, the objective of this study was to determine if PMPA could pose an environmental risk after soman exposure to a water environment. In this study, the toxicity and bioaccumulation assessments of PMPA were carried out on zebrafish. Histological examination was used to assess the toxicity of PMPA in zebrafish and revealed that PMPA has chronic toxicity in view of tissue injury. The contents of PMPA in whole zebrafish and tissues were determined after soman exposure. The result showed that PMPA bioaccumulated in the whole zebrafish and tissue, especially the liver and intestinal tissues. This is the first report showing that the hydrolyzate of a G-series chemical nerve agent could accumulate in organisms. This study offers novel insights into the environmental risk assessments associated with soman exposure to a water environment.

Current Progress for Retrospective Identification of Nerve Agent Biomarkers in Biological Samples after Exposure

Organophosphorus neurotoxic agents (OPNAs) seriously damage the nervous system, inhibiting AChE activity and threatening human health and life. Timely and accurate detection of biomarkers in biomedical samples is an important means for identifying OPNA exposure, helping to recognize and clarify its characteristics and providing unambiguous forensic evidence for retrospective research. It is therefore necessary to summarize the varieties of biomarkers, recognize their various characteristics, and understand the principal research methods for these biomarkers in the retrospective detection of OPNA exposure. Common biomarkers include mainly intact agents, degradation products and protein adducts. Direct agent identification in basic experimental research was successfully applied to the detection of free OPNAs, however, this method is not applicable to actual biomedical samples because the high reactivity of OPNAs promotes rapid metabolism. Stepwise degradation products are important targets for retrospective research and are usually analyzed using a GC–MS, or an LC–MS system after derivatization. The smaller window of detection time requires that sampling be accomplished within 48 h, increasing the obstacles to determining OPNA exposure. For this reason, the focus of retrospective identification of OPNA exposure has shifted to protein adducts with a longer lifetime. Compared to the fluoride-induced reactivation method, which cannot be used for aged adducts, digestive peptide analysis is the more elegant method for detecting various adducts, identifying more active sites, exploring potential biomarkers and excavating characteristic ions. Retrospective identification of biomarkers after OPNA poisoning is of primary importance, providing unambiguous evidence for forensic analysis in actual cases and judgment of chemical accidents. At present, degradation products, the nonapeptide from BChE adducts and Y411 from human serum adducts are used successfully in actual cases of OPNA exposure. However, more potential biomarkers are still in the discovery stage, which may prove inconclusive. Therefore, there is an urgent need for research that screens biomarker candidates with high reactivity and good reliability from the potential candidates. In addition, mass spectrometry detection with high resolution and reactivity and an accurate data processing system in the scanning mode must also be further improved for the retrospective identification of unknown agents.

Rapid, in situ detection of chemical warfare agent simulants and hydrolysis products in bulk soils by low-cost 3D-printed cone spray ionization mass spectrometry

Chemical warfare agents (CWAs) are toxic chemicals that have been used as disabling or lethal weapons in war, terrorist attacks, and assasinations. The Chemical Weapons Convention (CWC) has prohibited the use, development, production, and stockpiling of CWAs since its initiation in 1997, however, the threat of deployment still looms. Detection of trace CWAs post-deployment or post-remediation, in bulk matrices such as soil, often requires lengthy sample preparation steps or extensive chromatographic separation times. 3D-printed cone spray ionization (3D-PCSI), an ambient ionization mass spectrometric (MS) technique, provides a rapid, simple, and low-cost method for trace CWA analysis in soil matrices for both in-laboratory and in-field detection. Described here is the utilization of conductive 3D-printed cones to perform both rapid sampling and ionization for CWA simulants and hydrolysis products in eight solid matrices. The analysis of trace quantities of CWA simulants and hydrolysis products by 3D-PCSI-MS coupled to both a commercial benchtop system and a field-portable MS system is detailed. Empirical limits of detection (LOD) for CWA simulants on the benchtop MS ranged from 100 ppt to 750 ppb and were highly dependant on solid matrix composition, with the portable system yielding similar spectral data from alike matrices, albeit with lower sensitivity.

Poisoning by organophosphorus nerve agents and pesticides: An overview of the principle strategies and current progress of mass spectrometry-based procedures for verification

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Evidence of poisoning with organophosphorus (OP) nerve agents requires biomedical verification.

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OP nerve agents undergo common biotransformation pathways producing valuable biomarkers.

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Internationally accepted methods target remaining poison, hydrolysis products and protein-adducts.

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Mass spectrometry-based methods provide optimum selectivity and sensitivity for identification.

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Methods, strategies, current proceedings, quality criteria and real cases of poisoning are presented.

Intoxication by organophosphorus (OP) poisons, like nerve agents and pesticides, is characterized by the life-threatening inhibition of acetylcholinesterase (AChE) caused by covalent reaction with the serine residue of the active site of the enzyme (phosphylation). Similar reactions occur with butyrylcholinesterase (BChE) and serum albumin present in blood as dissolved proteins. For forensic purposes, products (adducts) with the latter proteins are highly valuable long-lived biomarkers of exposure to OP agents that are accessible by diverse mass spectrometric procedures. In addition, the evidence of poison incorporation might also succeed by the detection of remaining traces of the agent itself, but more likely its hydrolysis and/or enzymatic degradation products. These relatively short-lived molecules are distributed in blood and tissue, and excreted via urine. This review presents the mass spectrometry-based methods targeting the different groups of biomarkers in biological samples, which are already internationally accepted by the Organisation for the Prohibition of Chemical Weapons (OPCW), introduces novel approaches in the field of biomedical verification, and outlines the strict quality criteria that must be fulfilled for unambiguous forensic analysis.

Instantaneous monitoring of free sarin in whole blood by dry blood spot-thermal desorption-GC-FPD/MS analysis

Dry blood spot (DBS), a micro whole-blood sampling technique, enables rapid and self-blood collection; it is stable and economical. Currently, DBS filters require various sample preparation procedures specifically tailored for the target compounds, which are followed by GC-MS or LC-MS analysis. However, the small amounts of blood make the approach analytically challenging, mostly in terms of sensitivity and quantification. Herein, we introduce a new DBS concept for GC-compatible volatile to semi-volatile compounds in which DBS is directly coupled with thermal desorption analysis, thus eliminating time consuming treatments. Furthermore, to stabilize the target compound over the sampling DBS substrate, a commercial filter based on an extremely efficient trapping adsorption phase, styrene-divinylbenzene (SDVB), is first used. The performance of the new SDVB-DBS concept was demonstrated herein for monitoring the most volatile chemical warfare agent, sarin, which might be present in blood and the detection of which is usually challenging due to its rapid metabolism. This study encompasses adequate sampling and analysis method parametrization and validation, leading to a detection sensitivity of 100 pg sarin per 30 µL whole blood in 5-day-old samples, with a linear dynamic range of two orders of magnitude, adequate precision, and acceptable accuracy. Applying the method to an in-vivo mouse intranasal exposure experiment (3LD₅₀ GB) enabled the successful detection of 25-90 ng mL^-1 free sarin in blood samples drawn 2 min after exposure. The method's performance clearly emphasizes the potential of the new concept in "freezing the clock" for reactive whole blood media in pharmacokinetics and pharmacodynamics studies, as well as in applications in which informative and reliable monitoring of unstable target compounds and biomarkers is desired.