Mustard gas, or sulfur mustard, is one of the most harmful chemical warfare agents, causing severe blistering of the skin and mucous membranes upon contact. To enhance battlefield detection of this hazardous substance, chemists at Washington University in St. Louis have secured a $1 million contract from the Defense Threat Reduction Agency (DTRA) to develop a more efficient identification method.
Jennifer Heemstra (left) works in her laboratory with postdoctoral researcher Joseph Ibukun. Image Credit: Sean Garcia/Arts & Sciences
Quick and accurate detection of sulfur mustard is essential for minimizing exposure and mitigating harm, says Jennifer Heemstra, the Charles Allen Thomas Professor of Chemistry in Arts & Sciences and principal investigator of the new DTRA grant.
It is important to be able to detect sulfur mustard because once people are exposed, there is no antidote. Detection is key to preventing exposure, and currently there are not good technologies to do that rapidly in the field.
Jennifer Heemstra, Charles Allen Thomas Professor, Washington University in St. Louis
Mustard gas has been used in warfare since World War I, with documented cases in World War II and the Iran-Iraq conflict of the 1980s. While exposure is rarely fatal, it can cause serious injuries, including permanent eye damage, second- and third-degree burns, and severe respiratory issues. Even outside of active combat, service members, contractors, and civilians handling explosive ordnance may be at risk of exposure.
Current detection methods require costly equipment and complex sample preparation, making them impractical for real-time use in the field. The new research effort aims to change that.
Under the DTRA grant, Heemstra and her collaborators, including M.G. Finn at Georgia Institute of Technology, will develop a streamlined method for detecting vesicants—a broader class of chemical agents that includes sulfur mustard.
We will initially focus on model compounds that act like mustards, but that can be handled safely in the laboratory. This will allow us to test different molecular sensor designs, with the Heemstra lab and ours working together on complementary approaches.
M.G. Finn, Georgia Institute of Technology
The research team includes Joseph Ibukun, a postdoctoral research associate at WashU; Seth Taylor, a postdoctoral research associate at Georgia Tech; and Makenzie Walk, a graduate student at WashU.
Their approach relies on nucleic acid molecular recognition, using biomolecules that bind to specific vesicants and trigger a reaction producing a highly visible fluorescent signal.
Often sensors have a simple, linear output as in, the one molecule you detect produces one molecule of signal on the other end. Here we are planning to generate an amplified output so that for every molecule of toxin, you are generating several signal molecules so that you can detect them with the naked eye.
Jennifer Heemstra, Charles Allen Thomas Professor, Washington University in St. Louis
Her collaborators at Georgia Tech bring specialized expertise in generating amplified signals using dendrimers—synthetic molecules with a precisely structured, branch-like design.
Heemstra said, “For this kind of branched chain molecule, you generate more and more branches with every generation. After one reaction with a toxin molecule, we hypothesize that we can trigger a cascading reaction that will then release dye molecules at the end of each of the branch points.”
While countering weapons of mass destruction is crucial for military personnel, this research has significant implications for civilian safety as well.
Heemstra points to sarin as an example. In warfare, it’s deployed at high doses and can be lethal within minutes. However, certain organophosphate pesticides share a similar structure and biological mechanism, albeit with lower toxicity. Prolonged exposure to these pesticides can lead to chronic organophosphate poisoning.
Heemstra said, “Milder versions of the types of toxins that are used in warfighting and as chemical weapons show up in everyday life. When they are not handled properly, they can be a real threat to society and human health.”