There may soon be a new weapon in our
centuries-old battle against germs: the first durable coating that can quickly
kill bacteria and viruses and keep on killing them for months at a time.
Developed by a team of University of
Michigan engineers and immunologists, it proved deadly to SARS-CoV-2 (the virus
that causes COVID-19), E. coli, MRSA and a variety of other pathogens. It
killed 99.9% of microbes even after months of repeated cleaning, abrasion and
other punishment on real-world surfaces like keyboards, cell phone screens and
chicken-slathered cutting boards.
The coating could be a game changer in
traditionally germ-laden public spaces like airports and hospitals, according
to Anish Tuteja, a professor of material science and engineering at U-M and
co-corresponding author of the paper published in Matter.
“We’ve never had a good way to keep
constantly-touched surfaces like airport touch screens clean,” he said.
“Disinfectant cleaners can kill germs in only a minute or two but they dissipate
quickly and leave surfaces vulnerable to reinfection. We do have long-lasting
antibacterial surfaces based on metals like copper and zinc, but they take
hours to kill bacteria. This coating offers the best of both worlds.”
The coating, which is clear and can be
brushed or sprayed on, gets its durability and germ-killing power by combining
tried-and-true ingredients in a new way. It uses antimicrobial molecules
derived from tea tree oil and cinnamon oil, both used for centuries as safe and
effective germ killers that work in under two minutes. The coating’s durability
comes from polyurethane, a tough, varnish-like sealer that’s commonly used on
surfaces like floors and furniture.
“The antimicrobials we tested are
classified as ‘generally regarded as safe’ by the FDA, and some have even been
approved as food additives,” Tuteja said. “Polyurethane is a safe and very
commonly used coating. But we did do toxicity testing just to be sure, and we
found that our particular combination of ingredients is even safer than many of
today’s antimicrobials.”
The results of the study’s durability
tests suggest that the coating could keep killing germs for six months or
longer before its oil begins to evaporate and reduce its disinfectant power.
But even then, Tuteja says it can be recharged by wiping it with fresh oil; the
new oil is reabsorbed by the surface, starting the cycle again.
Tuteja estimates that the technology
could be commercially available within a year; it has been licensed to
Hygratek, a spinoff company that Tuteja founded with assistance from U-M
Innovation Partnerships.
The key challenge was to combine the oil
and polyurethane in a way that let the oil molecules do their germ-killing work
while preventing them from evaporating quickly. The research team — including
associate professor of materials science and engineering and biomedical
engineering Geeta Mehta, a co-corresponding author; and materials science and
engineering PhD students Abhishek Dhyani and Taylor Repetto, co-first authors —
found a possible solution in cross-linking, a well-known process that uses
heating to link materials together at the molecular level. The smaller oil
molecules readily combined with the cross-linking polymer molecules, forming a
stable matrix.
But to kill germs, the oil molecules
need to penetrate their cell walls, which they can’t do if they’re tightly
tethered into the matrix. Eventually, they found a middle ground by partially
cross-linking the materials — enough to keep some of the oil molecules free to
do their work, but keeping others bound tightly to the polyurethane.
“There was some trial and error, but we
eventually found that cross-linking only some of the oil did what we needed,”
Tuteja said. “The free oil tends to stay with the oil that’s cross-linked into
the matrix, helping the coating last longer.”
Once the basic recipe was set, the
researchers set about finding a combination of active ingredients that would
kill a wide variety of the germs that trouble humans most. To identify a
representative sample of microbes, they worked with co-corresponding authors
Christiane E. Wobus, an associate professor of microbiology and immunology, and
J. Scott VanEpps, an associate professor of emergency medicine, both at the U-M
Medical School. Ultimately, they found a precise balance of antimicrobial
molecules that were effective, safe and inexpensive.
Tuteja emphasizes that they’re not
locked into one specific formula; the team’s understanding of individual
ingredients’ properties enables them to tweak the formula for specific
applications or rebalance the antimicrobial agents to kill specific germs.
“It’s never our goal just to develop a one-off coating, but instead to develop a library of underlying material properties to draw from,” Tuteja said. “If we can understand those properties, then we can develop coatings to meet the needs of specific applications.”
Source: https://news.umich.edu/durable-coating-kills-covid-virus-other-germs-in-minutes/
Source: Durable
coating kills COVID virus, other germs in minutes – Scents of Science
(myfusimotors.com)
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