Polyurethane locks in the antimicrobial power of tea tree and cinnamon oils; the new technology could start making public spaces safer within a year
From: University of Michigan
August 26, 2020 -- 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."
The study was funded by
the Office of Naval Research, with additional support from the University of
Michigan, Marie Skłodowska-Curie Actions, the National Institutes of Health and
the Department of Defense, with raw materials provided by Covestro.
The University of
Michigan has applied for a patent based on this technology. Tuteja and the
University of Michigan have a financial interest in Hygratek.
https://www.sciencedaily.com/releases/2022/08/220826113318.htm
No comments:
Post a Comment