Sprayable coating shields surfaces from viruses and bacteria

Australian researchers say they have created a first-of-its-kind sprayable coating that can prevent the surface spread of infection from bacteria and viruses — including COVID-19 — over a sustained period. Described in the journal Advanced Science, the spray works in two ways: repelling viruses and bacteria through an air-filled barrier, and killing pathogens through microscopic materials if the layer becomes damaged or submerged for extended periods.

Co-lead author Professor Antonio Tricoli, from The University of Sydney, said the spread of viral and bacterial pathogens through contact with surfaces is a leading cause of infection worldwide. Surface contamination also plays a major role in the evolution of antibiotic-resistant bacterial strains.

“Without a barrier, viruses such as coronaviruses can stay on surfaces and remain infectious for up to a week,” Tricoli said. “Other viruses such as reoviruses, which can cause colds or diarrhoea, for instance, can remain on surfaces for several weeks, causing large outbreaks in health and aged care facilities.”

Applied in the same manner as spray paint (albeit in smaller quantities), the new coating is described as an alternative to standard disinfectants, which are becoming less effective and require regular reapplication, and as the only permanent surface layer proven to protect surfaces from contamination by viruses. It is also said to be safer than existing alternatives to disinfectant such as silver nanoparticles, with no harmful side effects and more stable potency.

The spray uses a combination of plastics strong enough to be considered an alternative to bulletproof glass, creating a coating that repels water. Tricoli explained, “Because the pathogens like to be in water, they remain trapped in the droplets and the surface is protected from contamination. If this mechanism fails, a secondary burst release of ions is triggered by carefully designed nanomaterials dispersed in the coating.”

The research team tested the mechanical stability and surface energy of the coating, as well as its ability to resist contamination from bacteria and viruses. Samples were submerged for extended periods of time and the sprayed surfaces were deliberately damaged to test the spray’s resilience against virus and bacteria contamination.

“For this study, we tested metal surfaces; however, in the past we have shown the spray can be applied to any surface, for example, blotting paper, plastic, bricks, tiles, glass and metal,” said co-lead author Professor David Nisbet, Director of The University of Melbourne’s Graeme Clark Institute. “Our coating successfully prevented up to 99.85% and 99.94% of the bacteria strain growth. We also saw an 11-fold reduction in virus contamination.

“The coating has been engineered through a simple and scalable technique with a careful choice of materials to provide ultra-durability. We also believe our explanation of the mechanism behind the antimicrobial and antiviral effects could significantly advance research in anti-pathogen technologies that could see affordable manufacture of an effective surface spray to protect people from viruses and bacteria.”

Nisbet said the coating could be applied to surfaces in public settings such as lift buttons, stair rails, surfaces in hospitals, nursing homes, schools or restaurants, to prevent the spread of common viruses and bacteria. The researchers have established a startup company to progress the technology and make the spray available commercially, potentially within three years.

Image caption: Where the square piece of glass sits lower than the orange liquid, this is the ‘parting of the waters’ effect caused by the surface energy/shield effect of the spray. Image credit: Cesar Nicolas.

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