A team at the University of Michigan has developed a coating for frequently touched surfaces that can rapidly kill a wide array of pathogens, including MRSA and SARS-CoV-2. The technology incorporates polyurethane that contains crosslinked compounds from essential oils with wide-spectrum anti-microbial action. The researchers fine-tuned the crosslinking process so that the oils were available to kill microbes but not sufficiently free to evaporate rapidly. Unlike anti-microbial surface coatings that are based on metals, such as copper or zinc, the new coating can kill microbes quite fast, in as little as two minutes. However, the coatings remain effective for as long as six months, when they can be recharged by painting them with some fresh oils.
The ongoing pandemic has highlighted the power of tiny microbes to bring our society to a grinding halt. However, if there is a silver lining, it is that this crisis has inspired numerous new technologies, from impressive mRNA-based vaccines to inexpensive ventilators. One important area of new technological development lies in disinfecting public spaces, such as train stations and airports, along with healthcare facilities where the most vulnerable people are.
This latest technology is a highly effective anti-microbial coating that can provide rapid antimicrobial action and long lasting efficacy. “We’ve never had a good way to keep constantly-touched surfaces like airport touch screens clean,” said Anish Tuteja, a researcher involved in the study. “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.”
These images show the bacterial load on a coated and uncoated computer keyboard, cell phone and cutting board with raw chicken. Images credit: Anish Tuteja
The coating is clear, and consists of polyurethane, a tough sealant that is often a component in varnishes. However, the material also includes antimicrobial compounds derived from essential oils, in this case cinnamon oil and tea tree oil. The nice thing about these components is that they were already classified as safe before use in the coating.
“The antimicrobials we tested are classified as ‘generally regarded as safe’ by the FDA, and some have even been approved as food additives,” said Tuteja. “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 researchers conducted some disgusting experiments to show that their technology can kill bacteria in challenging situations, including smearing surfaces with raw chicken and then testing if any of the microbes left on the surface survived contact with the coating. Thankfully, the coating worked well, so they can put the raw chicken away for now.
Study in journal Matter: Surfaces with instant and persistent antimicrobial efficacy against bacteria and SARS-CoV-2