Anti-COVID spray

Sprayable coating prevents spread of pathogens including Covid-19

Image credit: Cesar Nicolas, University of Melbourne

A sprayable coating that can prevent the surface spread of infection from bacteria and viruses, including Covid-19, over a sustained period has been developed by University of Sydney researchers.

The spray works by repelling viruses and bacteria through an air-filled barrier as well as killing pathogens through microscopic materials if the layer becomes damaged or submerged for extended periods. It uses a combination of plastics strong enough to be considered an alternative to bullet-proof glass.

A 2020 study showed that Covid-19 could survive for up to 28 days on surfaces such as mobile phone screens and banknotes.

The coating provides a reliable alternative to standard disinfectants, which are becoming less effective and require regular reapplication, and is safer than existing alternatives to disinfectant, the researchers said.

Testing has shown it has no harmful side effects and more stable potency – unlike the next most promising non-disinfectant agent that kills bacteria, silver nanoparticles.

The authors said the coating could be applied to surfaces in public settings such as lift buttons, stair rails, surfaces in hospitals, nursing homes, schools and restaurants, to prevent the spread of common viruses and bacteria.

Anti-COVID spray

Image credit: Cesar Nicolas, University of Melbourne

The spread of viral and bacterial pathogens through contact with surfaces is a leading cause of infection worldwide and 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. 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,” said Professor Antonio Tricoli, a researcher on the project.

“Like a lotus leaf, the surface spray creates a coating that repels water. 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 of ions is triggered by carefully designed nanomaterials dispersed in the coating.”

The team tested the mechanical stability and surface energy of the coating as well as its ability to resist contamination from bacteria and viruses by subjecting it to high concentrations of both.

The samples were submerged for extended periods of time and the sprayed surfaces were deliberately damaged to test the spray’s resilience against their contamination.

“We have identified the mechanical processes underpinning how the spray works and quantified its effectiveness in different environments,” said Professor David Nisbet.

“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. Our coating successfully prevented up to 99.85 per cent and 99.94 per cent of the bacteria strain growth. We also saw an 11-fold reduction in virus contamination.”

The spray is applied in the same manner as spray paint, although smaller quantities are needed.

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