Wearable Nanotech Could Combat Nerve Agents

Nanoparticles could someday provide a new way to help soldiers fight back against deadly nerve agents on the frontline.

In a new study, Northwestern University scientists developed a nanoparticle-based compound that, when mixed into clothing dyes, could limit the impact of chemicals commonly found in pesticides, insecticides and nerve agents. 

Manufacturers potentially could add the nanoparticles to clothing used by those most at risk, such as farmers’ masks and gloves or soldiers’ uniforms and tactical gear. Or, if someone is exposed to a potentially deadly chemical, they could spray their clothing with water mixed with the compound to deactivate the chemical before its damaging effects take hold.

The study was published recently in the journal ACS Nano.

“Our bioinspired melanins are non-toxic and can be used as an additive in clothing or facemasks and beyond. We previously have shown the ability to use them in dyeing synthetic fabrics,” said Northwestern’s Nathan Gianneschi, a corresponding author on the study. “You could imagine using this approach to make protective clothing or breathing equipment for workers who make or use these materials to provide everyday protection.”

Gianneschi is a co-corresponding author with Omar Farha. Farha is the Charles E. and Emma H. Morrison Professor of Chemistry in the Weinberg College of Arts and Sciences and chair of the Department of Chemistry and professor (by courtesy) of chemical and biological engineering at Northwestern Engineering. Gianneschi is the Jacob and Rosaline Cohn Professor of Chemistry at Weinberg and a professor of materials science and engineering and biomedical engineering at the McCormick School of Engineering.

In the new study, Gianneschi, Farha, and their teams sought to mimic how nature can counteract substances like organophosphorus compounds, the toxic chemicals found in nerve agents and pesticides. Specifically, they explored allomelanin, a renewable, biodegradable pigment that deepens the color of plants and fungi.

To develop the new nanoparticles, the researchers started with synthetic allomelanin. Naturally porous, allomelanin contains a network of tiny pores that can grab and capture harmful chemicals. Then, they added a zirconium cluster, a metal cluster with an ability to catalyze chemical reactions. Working together, the allomelanin absorbed the toxic chemicals and the zirconium destroyed them.

“This intrinsic microporosity is required,” said Sofia Aman, a graduate student in Gianneschi’s lab and the study’s co-first author. “When we tested other melanin-like materials, they didn’t work as well. So, we do need this porosity, and that just makes this allomelanin much more unique and a better substrate.”

For the chemical reaction to work, the environment needs to be entirely basic—reaching a pH of 10 or higher. Instead of adding an external basic compound, the researchers incorporated basic chemical groups onto the nanoparticles’ surface. Then, water activates the particles, enabling them to break down the harmful chemicals. When the organophosphorus compound breaks down, it releases two chemicals—and this is where the danger lies.

While one of the chemicals (dimethyl phosphate) is nontoxic, the second chemical (methyl nitrophenyl) stops enzymes in the blood from breaking down a critical neurotransmitter, acetylcholine. If the enzymes cannot break down acetylcholine, it builds up in the nervous system and prevents the brain from communicating with the rest of the body.

But the new study found researchers can limit exposure, both by decreasing the amount of toxic chemicals and their potency. The allomelanin grabbed hold of the toxic chemical and broke it down and left the nontoxic chemical alone. Within 10 minutes, the toxic byproduct decreased by 50 percent and continued to decrease with more melanin and with sunlight exposure.

“Previously, our group developed catalytic metal-organic frameworks (MOFs), which are exceptionally powerful materials in the absorption and processing of chemical warfare agents,” Farha said. “This work takes those learnings and advances them towards melanin-inspired materials which are inherently adhesive, acting as dyes for various fibers and fabrics. In fact, melanin is nature’s pigment, as well as being an efficient absorbent of small molecules and heavy metal ions in biological organisms. We couple those natural functions with catalysis using a combination of synthetic inorganic chemistry, from my group and biomimetic polymer science from Gianneschi’s team.” 

Researchers also found that melanin had additional natural benefits. Melanin reacts with sunlight and absorbs heat. So, when allomelanin is exposed to sunlight, the detoxification process accelerates.

“We have worked on melanin for over 12 years, trying to learn about its myriad functions in nature and learning how to optimize, develop, and engineer mimetic materials for scalable, translational applications,” Gianneschi said. “This provides us with a treasure trove of approaches and materials to optimize and develop for applications like this. In many ways, it’s a proof of concept for a new direction in how we think about protective materials and coatings design."