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University Develops Antibacterial Coating
A team of engineers and immunologists from the University of Michigan have recently announced the development of a new durable coating capable of killing bacteria and viruses quickly and for long periods of time.
Anish Tuteja, professor of material science and engineering at U-M and co-corresponding author of the study, shared that the coating could be a game changer in traditionally germ-laden public spaces like airports and hospitals.
Other members of the research team include associate professor of materials science and engineering and biomedical engineering Geeta Mehta, a co-corresponding author; and materials science and engineering Ph.D. students Abhishek Dhyani and Taylor Repetto, co-first authors.
“Surfaces with instant and persistent antimicrobial efficacy against bacteria and SARS-CoV-2” has since been published in Matter.
Coating Research
According to the university, the recently developed antibacterial coating proved deadly to SARS-CoV-2 (the virus that causes COVID-19), E. coli, MRSA and a variety of other pathogens.
In further research, the team found that even after months of cleaning and traditional wear and tear on real-world surfaces like keyboards, cell phone screens and chicken-slathered cutting boards, the coating still killed 99.9% of microbes.
“We’ve never had a good way to keep constantly-touched surfaces like airport touch screens clean,” Tuteja 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 clear polyurethane coating, which can be applied by brush or spray methods, uses a combination of antimicrobial molecules derived from tea tree oil and cinnamon oil. The university notes that while tree oil and cinnamon have long been used as effective germ killers, polyurethane is what gives the coating its durability.
“The antimicrobials we tested are classified as ‘generally regarded as safe’ by the FDA, and some have even been approved as food additives,” Tuteja added. “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 real trick to making sure the coating was effective, however, was figuring out how the oils and polyurethane could be combined in such a way that would kill bacteria and viruses without evaporating too quickly.
Because oil molecules need to penetrate their cell walls to kill germs, the oils couldn’t be too constrained within the matrix. In order to have some of the oil molecules free to do their work and others to bind with the polyurethane, the team had to partially cross-link the materials to meet the coating’s desired effectiveness.
“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 a formulation was set, researchers looked into other active ingredients that could be used to kill some of the more troublesome germs. For this portion of the research, the team 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.
As a result, the team was able to find a precise balance of antimicrobial molecules that were effective, safe and inexpensive.
Upon additional durability tests, the team suggests that the coatings could keep killing germs for six months or longer before the oils begin to evaporate. However, when wiped with fresh oils, Tuteja says that the coating can “recharge.”
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. He also adds that the team isn’t “locked into one specific formula” and that they hope to continually tweak the coating for specific applications.
“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 Skodowska-Curie Actions, the National Institutes of Health and the Department of Defense, with raw materials provided by Covestro.
The University of Michigan has since applied for a patent based on this technology.
Other Recent Research
Earlier this summer, a team of Australian researchers developed a sprayable coating capable of preventing the surface spread of infection from bacteria and viruses, including COVID-19.
Developed over a period of five years, the spray coating research was headed by co-lead author University of Sydney’s School of Biomedical Engineering Professor Antonio Tricoli and Director of the University of Melbourne's Graeme Clark Institute, Professor David Nisbet.
Reported to be a first of its kind, the spray is made up of a combination of plastics strong enough to be considered an alternative to bullet-proof glass.
According to the University of Sydney, the developed spray coating provides a more reliable alternative to standard disinfectants, which are becoming less effective and require regular reapplication, but it is the only permanent surface layer proven to protect surfaces from virus contamination.
Researchers note that the coating is also safer than existing alternatives to disinfectants, with no harmful side effects and more stable potency.
In April, Russian researchers from Tomsk State University have developed a paint designed to neutralize common pathogens and reduce nosocomial (hospital-acquired) infections. Supported by a number of governmental programs, including the Priority 2030 program, the new coating is slated to be used on the walls of two Tomsk Region hospitals.
Reportedly enhanced with biocidal nanoparticles, the new paint aims to neutralize a number of common pathogens and reduce nosocomial infections.
According to TSU, the paint Premia has two types of composition. Noted to be equal in effectiveness, only one of the paints has been tested and certified, while the second is an upgraded, cheaper version with the aim of making the paint more available to potential buyers.
In preliminary testing of both versions, developers add that the concentrated nanoparticles proved their effectiveness against a widespread collection of common nosocomial infections.
Pilot testing of the paint will be conducted in Timiryazev Central Regional Hospital and B.I. Alperovich City Clinical Hospital No 3, where biocidal paint is needed due to high risk of infection. In both locations, the paint will be applied in emergency rooms, wards, treatment rooms, relatively clean areas and, in one hospital, a manipulation room.
In the six months following the announcement, scientists planned to take wipe-samples to determine the presence of bacteria and viruses, determine the efficiency of different types of compositions and investigate nanoparticle activity.
