University of Minnesota engineers are studying whether a coating made out of a tree extract could be applied to masks to increase their protectiveness against the corona­virus that causes COVID-19.

The study led by Boya Xiong, a U assistant professor of engineering, was inspired by the antimicrobial and antiviral properties of proteins from Moringa oleifera, a tree native to India that is grown in domestic gardens because its seeds can be consumed as vegetables and its leaves brewed as tea.

The research goal is to crush the seeds and mix them with water to form a coating that can be applied to masks, because the proteins appear to bind specifically with the coronavirus in a way that will trap it, Xiong said.

"We hope that having this layer of protein on the textile would enhance the removal of virus in the droplets or aerosols coming from people talking, inhaling or coughing."

The federally funded study is the latest do-it-yourself concept explored at the U, where an anesthesiologist last year made a makeshift ventilator out of a toolbox and $150 in parts, and an apparel designer this year created a mask design out of vehicle filters that could be assembled in the event of a supply shortage.

U engineers also worked with the Minnesota Orchestra on ways to protect musicians from infection during performances and simulated how viral buildup can occur based on airflow patterns in elevators, stores and classrooms.

Mask-wearing has been one of the touchiest and most politically divisive strategies in the COVID-19 pandemic, with debates over school mask-wearing requirements provoking arguments and confrontations at local government and school board meetings.

Mask-wearing rates fall along political lines but have plummeted overall in Minnesota following the end of an indoor mask mandate in May. More than 90% of Minnesotans wore masks in public most or all the time in February, but that rate dropped below 20% in July before rebounding above 45% this month, according to survey data published by Carnegie Mellon University's COVIDcast website.

While some studies have questioned whether masks have reduced viral transmission in the pandemic, federal and state health officials encourage their use in counties with high transmission levels and K-12 schools.

A recent U and Mayo Clinic study used two particle-emitting mannequins to find that masks worked best as source control — preventing wearers from spreading viral particles to others — but that risks were lowest when both parties were wearing them.

Two studies published last week by the Centers for Disease Control and Prevention also showed that the odds of school outbreaks were higher in schools with no mask requirements. However, those studies might not have proved cause and effect, because it's possible that schools with mask mandates take COVID-19 risks more seriously and have other methods of infection control in place, said Michael Osterholm, director of the U's Center for Infectious Disease Research and Policy.

"So often, masks are markers for all of the other things that are going on," he said.

Proper fit also has been a concern with even the most effective masks, which need to fit snugly over the nose and below the chin to reduce viral transmission. Xiong said solutions to all those problems are needed but could only be aided by an easy way to make masks work better.

"We all hope that this COVID will be gone," she said, "but I think the bigger reality probably ... is that this will be more like a really bad flu and there will be more outbreaks where people still need to wear masks."

Xiong has studied the tree extract protein for five years, discovering its antiviral qualities and testing how it removes bacterial and viral particles from water.

Challenges ahead include finding simple ways to charge masks before the coating is applied so the proteins bind to the fibers in a way that can capture viral particles.

Breathability will be studied as well, but Xiong said the proteins from the coating are tiny and shouldn't clog the pores in the masks that allow air intake.

Jeremy Olson • 612-673-7744