Materials

Practical antibacterial coating is activated by ambient light

Practical antibacterial coatin...
The coating has been successfully used to eradicate E. coli bacteria
The coating has been successfully used to eradicate E. coli bacteria
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The coating has been successfully used to eradicate E. coli bacteria
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The coating has been successfully used to eradicate E. coli bacteria

While we've already heard about light-activated germ-killing coatings, they generally require either ultraviolet or high-intensity light. A new one, however, works with regular low-intensity light, as might be found in offices or waiting rooms.

Developed via a collaboration led by scientists at University College London – and drawing upon a previous study –the antibacterial coating is made up of tiny clusters of chemically-modified gold embedded within a polymer, along with a dye known as crystal violet.

The latter has previously been shown to kill harmful bacteria on its own, although it requires exposure to either UV or very bright light. This causes it to produce chemically-reactive types of oxygen, called reactive oxygen species, which lethally damage the microbes' DNA and protective membranes.

Neither type of light is particularly practical or unobtrusive to use in public spaces, plus ultraviolet light is harmful to humans. Thanks to the addition of the gold, though, the dye in the new coating is triggered to produce hydrogen peroxide – which is a reactive oxygen species – when exposed to ambient light.

In lab tests, surfaces were covered with the coating, inoculated with either E. coli or S. aureus bacteria, and then exposed to light with an average intensity of just 312 lux – by contrast, other coatings require at least 3,000 lux in order to work. A significant number of the S. aureus were killed off within six hours, with a similar reduction in E. coli occurring after 24 hours.

On control surfaces, in which a coating was applied that contained the polymer and the dye but no gold, there was no reduction in bacteria.

"The gold clusters in our coating are key to generating the hydrogen peroxide," says Prof. Asterios Gavriilidis, senior author of a paper on the study. "Given the clusters contain only 25 atoms of gold, very little of this precious metal is required compared to similar coatings, making our coating attractive for wider use."

The paper was published this week in the journal Nature Communications.

Source: University College London

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