Losing Your Nerve (Agents)
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In 1938, German chemist Gerhard Schrader was attempting to make pesticides that were more effective. Instead, he accidentally discovered one of the most dangerous weapons of war ever produced: the nerve agent, sarin (Amarasingam, 2017). In the years that followed, German and British governments discovered analogues to the original chemical, and governments began producing stockpiles of such weapons. Since then, nerve agents have been used in terrorist attacks and assassination attempts (Stone, 2020). All nerve agents work the same way, by inhibiting the enzyme acetylcholinesterase. This leads to a buildup of acetylcholine in the central and peripheral nervous system, which can cause a myriad of negative effects on the body. These effects include profuse sweating, vomiting, altered mental state, convulsions, and paralysis of muscles leading to death (CDC, 2018). Since 1993, the production and stockpiling of these weapons has been banned by the Chemical Weapons Convention, and countries were required to destroy their stockpiles. (Mirjana Čolović, 2013).
Unfortunately, destruction techniques for these chemicals are dangerous, unsustainable, and expensive. They require large amounts of water and caustic compounds, such as sodium hydroxide, which degrade the nerve agents using hydrolysis. These compounds are difficult to dispose of safely even after the threat of the nerve gas has been eliminated, adding more unnecessary steps to the stockpile destruction process (CDC, 2018). The British military recently put out a call to solve this problem: they were looking for a material that could isolate and destroy bulk stockpiles of nerve agents and mustard gases. Of the 27 proposals put forth by scientists around the globe, only 2 were selected to receive funding. One of these projects was co-led by Dr. Barry Blight, from the University of New Brunswick, alongside Dr. Simon Holder, from the University of Kent.
Their approach to this problem had two components. First, a styrenic poly high internal phase emulsion (pHIPE) is used to absorb and contain the nerve agent. Second, a metal-organic framework (MOF) catalyzes the hydrolysis reaction used to degrade the nerve agent. A pHIPE is essentially a reverse micelle. Ordinary micelles are formed when a hydrophobic substance is placed in water, resulting in emergence of packets of the substance surrounded by water (think: oil in water). In this case, water is added to a material, polystyrene, and micelles are formed with water on the inside (think: water in oil). The organic phase is then polymerized around the water particles, followed by removal of the water from the material, leaving behind an extremely porous polymer solid. In this project, this meant that the end result was a styrofoam-esque substance containing a large number of tiny pores. Metal-organic frameworks are porous solids themselves, containing metals linked to organic ligands. MOF-808, the compound used in this work, contains Zirconium as the metal. This material is the catalytically active component of the system. It uses water to facilitate the hydrolysis of the nerve agent. The MOF is contained within the pores of the pHIPE, allowing the material to both sequester and neutralize the nerve agents using only ambient humidity.
MOF-808 and pHIPE work together to make a catalytically reusable, easily transportable, and safer option for destroying nerve agent stockpiles.
When asked about his research, Dr. Blight points to the “dichotomy of porosity” as his favourite part of the project.
“MOFS are porous solids, as well as the foam (pHIPE) is a porous solid. I like how the two materials work together with the different pore sizes to facilitate the containment and then the degradation. The containment happens in the big pores [the pHIPE], and the degradation happens in the small pores [MOF-808].”
With interview requests from British news networks, the CBC, and great feedback from peers, it is clear that the project was a success. The team is now working on scaling up the amount of material produced so it can be used on an industrial scale. To do this feasibly, they are first trying to reduce the amount of the expensive MOF-808 necessary to catalyze the reaction, which is the limiting factor in how much can be produced at this time.
To students who are interested in using research to solve real-world problems such as this one, Dr. Blight emphasizes that good scientists need strong work ethic more than good grades.
“The harder you work, the luckier you get. If you work really hard, you’re bound to have a couple of hits on things that work, and then those are the things you pursue until you can’t pursue them anymore. Those successful hits are what drive innovation, and you aren’t going to get innovation without failing a few times or without having to work around problems.”
References
Amarasingam, A. (2017, April 07). A History of Sarin as a Weapon. Retrieved January 11, 2021, from https://www.theatlantic.com/international/archive/2017/04/sarin-syria-assad-chemical-nazi/522039/
CDC. (2018, April 04). Retrieved January 11, 2021, from https://emergency.cdc.gov/agent/vx/basics/facts.asp
Colović, M., Krstić, D., Lazarević-Pašti, T., Bondžić, A., & Vasić, V. (2013, May). Acetylcholinesterase inhibitors: Pharmacology and toxicology. Retrieved January 11, 2021, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3648782/
Stone, Richard. (2020, September 08). How German military scientists likely identified the nerve agent used to attack Alexei Navalny. Retrieved January 11, 2021, from https://www.sciencemag.org/news/2020/09/how-german-military-scientists-likely-identified-nerve-agent-used-attack-alexei-navalny