Detection Of Organophosphate Nerve Agents Research Articles

Portable liquid crystal droplet array in the capillary for rapid and sensitive detection of organophosphate nerve agents

In this study, we report formation of the liquid crystal (LC) droplet array in the capillary and demonstrate its application in rapid, sensitive, and label-free detection of the dimethyl methylphosphonate (DMMP) vapor for the first time. When Cu(ClO4)2-doped LC droplets encounter DMMP, the optical response of the LC changes from the dark appearance to the bright appearance in 90 s. It is caused by the stronger coordination interaction of Cu(ClO4)2 with the phosphoryl group of DMMP than the nitrile group of 4-cyano-4′-pentylbiphenyl (5CB). The limit of detection reaches as low as 2.0 ppb. Interestingly, the optical response of the LC droplets changes from the bright appearance to the dark appearance in 10 min after putting the LC sensors in fresh air. Noteworthy, the LC droplets also show excellent performance even after used for 12 times and still work very well after the storage at room temperature for 2 weeks. Overall, this portable, low-cost, and reusable LC sensing platform has remarkable sensitivity, high selectivity, excellent reversibility, and very good stability, which makes it very promising in the detection of the organophosphate nerve agents.

Selective detection of organophosphate nerve agents using microplasma device

A newly designed microplasma device can detect two parts of the nerve agent components simultaneously which enhances the selectivity in analysis.

Automated detection of organophosphate warfare gases (nerve agents) in air based on micro-SIA – lab-on-valve system

Summary Equipment for fast and accurate detection of organophosphate nerve agents is developed and tested. The method is based on the spectrophotometric monitoring of the enzyme activity of butyrylcholinesterase after its contact with air in a special absorption unit (a “scrubber”) developed for the purpose. The scrubber was made from a glass tube filled with glass beads (diam. 3 mm) and filled with approx. 5 ml of butyrylcholinesterase in a phosphate buffer of pH 7.4. The air sample was bubbled through this solution for 20 s at a flow rate of 80 l hour −1 . Thereafter 8 μl of the enzyme solution were aspirated into the micro-SIA-LOV analyzer and the activity of the enzymes were evaluated by using Ellman's reagent, i.e. 2.5 mmol l −1 butyrylthiocholine iodide and 0.25 mmol 5,5′-dithiobis (2-nitrobenzoic acid). The absorbance of the coloured reaction product was measured at 412 nm after the reaction time of 60 s. The residue of the absorption liquid was washed away from the absorber and the system was washed with the enzyme solution prior to next analysis. The contaminated air caused partial inhibition of the enzyme activity of the absorption liquid. The activity of the contaminated sample was compared with the activity of the unaffected enzyme (blank measurement). The analysis was controlled by two PCs. The effect of the concentration of analyte in the absorption liquid on the enzyme activity was tested for 10 −5 –10 −9 mol l −1 sarin. A single analysis (including the absorption step) took

Colorimetric Detection of Warfare Gases by Polydiacetylenes Toward Equipment‐Free Detection

AbstractRationally designed polydiacetylene (PDA) molecules have been developed for rapid, selective, sensitive, and convenient colorimetric detection of organophosphate (OP) nerve agents, a mass destruction weapon. Oxime (OX) functionality was incorporated into diacetylene molecules to utilize its strong affinity toward organophosphates. The diacetylene molecules having an OX functional group (OX‐PDA) were self‐assembled to form PDA liposomes in an aqueous solution. Upon exposure to organophosphate nerve agent simulants, OX at the OX‐PDA liposome surface interacts with nerve agent simulants, which results in intraliposomal repulsive stress due to steric repulsion between OP‐occupied OX units at the liposome surface as well as interliposomal aggregation induced by increased hydrophobicity of the liposome surface via OP‐OX complex formation. The resulting intra‐ and interliposomal stress causes disturbance of the conjugated backbone of OX‐PDA, producing color change as a label‐free and sensitive sensory signal. The effects of molecular structure on selectivity and sensitivity of OX‐PDA liposome solution, OX‐PDA liposome‐embedded agarose gels, and OX‐PDA liposome‐coated cellulose acetate membranes were systematically investigated. The optimized OX‐PDA liposome in the solid state showed selective and rapid optical transition upon exposure down to 160 ppb of diisopropylfluorophosphate (DFP), a nerve agent simulant. The results provide an insightful molecular design principle of PDA‐based colorimetric sensor and suggest portable sensory patches for rapid, selective, sensitive, and convenient colorimetric detection of organophosphate nerve agents.

A novel organophosphorus hydrolase-based biosensor using mesoporous carbons and carbon black for the detection of organophosphate nerve agents

To detect organophosphate chemicals, which are used both as pesticides and as nerve agents, a novel biosensor based on organophosphorus hydrolase was developed. By using mesoporous carbon (MC) and carbon black (CB) as an anodic layer, the sensitivity of the sensor to p-nitrophenol (PNP), which is the product of the organophosphorus hydrolase reaction, was greatly improved. The MC/CB/glass carbon (GC) layer exhibited an enhanced amperometric response relative to a carbon nanotube (CNT)-modified electrode because it promoted electron transfer of enzymatically generated phenolic compounds (p-nitrophenol). The well-ordered nanopores, many edge-plane-like defective sites (EDSs), and high surface area of the MC resulted in increased sensitivity, and allowed for nanomolar-range detection of the analyte paraoxon. Thus, MCs are suitable for use in real-time biosensors. Under the optimized experimental conditions, the biosensor had a detection limit of 0.12μM (36 ppb) and a sensitivity of 198nA/μM for paraoxon.

Acetylcholinesterase: Converting a vulnerable target to a template for antidotes and detection of inhibitor exposure

Applications of recombinant DNA technology, chemical synthesis on biological templates and fluorescence detection of organophosphorylation provide unexplored avenues for development of antidotes and approaches for remote detection of organophosphate nerve agents and pesticides. We discuss here how acetylcholinesterase (AChE), through appropriate mutations, becomes more susceptible to oxime reactivation. Since the reaction between organophosphate and the mutated enzyme remains rapid, regeneration of active enzyme by oxime becomes the rate-limiting step in the process to complete a catalytic cycle for generation of active enzyme. Accordingly, “Oxime-assisted Catalysis” by AChE provides a potential means for catalyzing the hydrolysis of organophosphates in plasma prior to their reaching the cellular target site. In turn, AChE, when conjugated with organophosphate, is employed as a template for ‘click-chemistry, freeze-frame’ synthesis of new nucleophilic reactivating agents that could potentially prove useful in AChE reactivation at the target site as well as in catalytic scavenging of organophosphates in plasma. Finally, substituted AChE molecules can be conjugated to fluorophores giving rise to shifts in emission spectra for detection of dispersed organophosphates. Since external reagents do not have to be added to detect the fluorescence change, the modified enzyme would serve as a remote sensor.

Capillary Electrophoresis Microchips for Separation and Detection of Organophosphate Nerve Agents

A miniaturized analytical system for separating and detecting toxic organophosphate nerve agent compounds, based on the coupling of a micromachined capillary electrophoresis chip with a thick-film amperometric detector, is described. Factors influencing the on-chip separation and detection processes have been optimized. Using a MES buffer (20 mM, pH 5.0) running buffer, a 72-mm-long separation channel, and a separation voltage of 2000 V, baseline resolution is observed for paraoxon, methyl parathion, fenitrothion, and ethyl parathion in 140 s. Such miniaturization and speed advantages are coupled to submicromolar detection limits and good precision. Applicability to spiked river water samples is demonstrated, and the implications for on-site environmental monitoring and rapid security screening/warning are discussed.