Can protective clothing be reused without disinfection? This hydrogel may degrade the poison "in situ"

Nerve agents based on organophosphorus are one of the most toxic chemicals known to man. Recently, the journal Chemical Catalysis under Cell Press published a study online. Scientists at Northwestern University in the United States have developed a hydrogel integrated with zirconium-based metal organic frameworks (MOFs) that can quickly degrade the chemical warfare. Organophosphate nerve agent.

"This research work in the zirconium-organic molecular framework, increased the cross-linking of polyethyleneimine epoxides, and developed a hydrogel that can be maintained under ventilated conditions, which can hydrolyze several typical organophosphates almost instantaneously. Nerve agents, to achieve the detoxification of the contact surface, are all innovations based on the previous experiment of the same kind in 2018, representing a key step towards the production of protective equipment for the instantaneous detoxification of nerve agents under actual conditions." Chinese Academy of Sciences Jiang Tao, a senior engineer at the Biology Research Center of the Institute of Genetics and Developmental Biology, said in an interview with a reporter from Science and Technology Daily.

Toxic mechanism similar to insecticides

Nerve agents are often discolored, so how do organophosphorus-based nerve agents cause harm to humans?

In this regard, Jiang Tao explained that Organophosphates (OPs) are a general term for a class of chemical pesticides, and their main function is to covalently modify the acetylcholinesterase (AChE) of insects, resulting in the ability to hydrolyze acetylcholine by esterase. Inhibition.

"Animal nerve conduction depends on the neurotransmitter between nerve synapses-acetylcholine and its receptor. Under normal circumstances, acetylcholine, which is a neurotransmitter, acts between nerve synapses. Acetylcholine is activated after being secreted by synthetic cells. The acetylcholine receptors on the surface of adjacent cells transmit the signal down and are immediately hydrolyzed by acetylcholinesterase so that the receptor can be activated by the next release of acetylcholine." Jiang Tao said.

Jiang Tao analyzed that if acetylcholinesterase is combined with organophosphorus pesticides, resulting in loss of activity, acetylcholine cannot be removed in time, a large amount of acetylcholine accumulates at the synapse, the acetylcholine receptors in the postsynaptic membrane are continuously activated, and the postsynaptic nerve fibers Be in a state of excitement for a long time. At the same time, the normal nerve impulse conduction at the synapse is blocked, and the poisoned insects will immediately experience high excitement and convulsion of muscles and other tissues, and finally paralyze and die.

In fact, the research on acetylcholinesterase has a history of more than 70 years, and there are more than 20,000 related scientific papers.

"The difference between human acetylcholinesterase and insects is not great enough. Many organophosphorus pesticides are also neurotoxic to humans and may be absorbed by the skin. This also makes people worry about being used in chemical weapons. For example, This is the case with the sarin poison that Nazi Germany tried to put into production during World War II.” Jiang Tao pointed out.

Physical protection is the primary line of defense

In the face of organophosphorus nerve agents, humans usually use physical protection and drugs to detoxify.

Jiang Tao explained that human protection against organophosphorus pesticides is first of all physical protection, such as using gas masks or even full-body protective clothing to prevent the inhalation of poisons and their contact with the skin.

For poisoned higher animals, organophosphorus pesticides first poison the liver and kidneys, and cause severe abdominal pain. At the same time, they can also poison the brain, and then the heart function will also be harmed.

Experts analyze that organophosphorus pesticides can be poisoned by inhalation or absorption through the skin. Among them, accidental poisoning in children is more common, mostly due to accidental consumption of food contaminated by organophosphorus pesticides (including fruits, vegetables, dairy products, grain, and poisoned livestock and aquatic products, etc.); misuse of toys or pesticides contaminated with pesticides Containers; inappropriate use of organophosphorus pesticides to kill mosquitoes, lice, fleas, bed bugs, and cockroaches, as well as to treat skin diseases and deworming; mothers breastfeed their babies without washing hands and changing clothes carefully after using pesticides; packaging organophosphorus pesticides Use plastic bags to make urine pads or use soil-covered trousers to replace urine pads with sandy soil sprayed with organophosphorus pesticides; playing near the fields sprayed with organophosphorus pesticides may cause inhalation poisoning.

Therefore, Jiang Tao said that the pesticide authority of the Chinese government has banned the use of highly toxic organophosphorus pesticides in an orderly manner.

"After organophosphorus pesticides are poisoned, detoxification can be done as soon as possible with drugs such as pralidoxime. It can remove the organophosphorus modified part from the acetylcholine ester, and roughly restore the quantity and activity of acetylcholine ester. However, the human acetylcholine ester is The complexes covalently modified by phosphorus compounds will undergo further irreversible structural changes over time. This change is called aging. After aging, the acetylcholinesterase cannot recover its activity. If the organophosphorus pesticides are less toxic, the dosage is limited, and the tissues are not. Necrosis, the body is not dead, and it can be completely replaced by the expression of new enzyme molecules from the cells and gradually return to normal." Jiang Tao said.

In 2018, a project involving US Army chemical and biological experts reported for the first time that it systematically studied the effectiveness of the solvolysis of organophosphorus compounds using MOFs.

"The results show that the use of organic framework methanol gel with zirconium as the central metal can solvate several organophosphorus compounds that simulate chemical weapons (chemical warfare agents) without consuming this zirconium-organic framework compound, which is originally used as a structure. The zirconium-organic framework of the framework actually acts as a catalyst for the solvolysis of organophosphorus at the same time, which should be regarded as an unexpected gain.” Jiang Tao said.

New materials are easy to use on protective clothing

This year, Northwestern University’s Institute of Chemistry and International Nanotechnology, the U.S. Army’s Combat Capability Development Command Chemical Biology Center, and Northwestern University’s Department of Chemistry and Biological Engineering jointly published a paper entitled "Zirconium-based Metal-Organic Framework Hydrogel Composite Material Nearly Instant Catalytic hydrolysis of organophosphate nerve agents."

Unlike the existing powdered MOF absorbent material, this hydrogel material does not require the addition of water, so it is more convenient to use on protective masks or clothing. Omar Farha, a professor of chemistry at Northwestern University and the corresponding author of the paper, said: “The use of chemical weapons in recent global conflicts reflects the urgent need for personal protective equipment and the urgency of mass destruction of chemical weapons stockpiles. In this work, we will MOFs and amine-containing cross-linked hydrogels are integrated into the fabric to establish an appropriate microenvironment, which in turn promotes the rapid degradation of nerve agents and provides real-time protection."

Although MOFs have previously proven their ability to quickly decompose organophosphorus preparations and similar analogues in the laboratory, it has been proved that these powder adsorbents are difficult to integrate directly into protective cloths. When the neurotoxin binds to the zirconium 6 cluster, it usually deactivates the powder and fiber composite catalyst. This shortcoming requires the use of alkaline solutions to regenerate the catalytic sites of MOFs, which will not prevent MOFs from being used to eliminate stored chemical weapons, but will hinder their use in protective equipment.

To overcome this challenge, Farha and colleagues designed a MOF-based fabric composite system that uses water in an amine-based hydrogel to break down nerve agents.

"The protective clothing containing this kind of hydrogel on the surface can hydrolyze the organophosphorus warfare agent it comes into contact with, which means that the surface protective clothing does not need to be disinfected, and it can be reused only by ensuring the moisture in the gel. This is compared with the usual protective clothing. The clothes must be disinfected and thoroughly cleaned and verified before they can be reused, which has certain advantages.” Jiang Tao explained.

"The research originated from the chemistry of metal-organic compounds, and has continued to grow since the 1960s. It has branched out into metal-organic compounds, transition metal organic compounds, metal cluster compounds, transition metal cluster compounds, metal-organic framework compounds, etc., From pure basic research, new molecular products with practical significance or potential functions have been developed.” Jiang Tao pointed out that this shows an important feature of scientific and technological development. When conducting basic research, I don’t know what will be discovered tomorrow, let alone the future development. What else will it bring? Scientists study and upgrade the structure of a molecule, which will also bring unexpected new functions. Science and technology complement each other, and continue to obtain theoretical and innovative results.

Source: Stdaily

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