Although we’ve heard of light-activated bactericidal coatings, they usually require uv or high-intensity light. However, a new antibacterial coating can be activated by low-intensity light that is normally used in the office or waiting room. The coating was developed by a team led by scientists at University College London and builds on previous research that consists of tiny chemically modified gold clusters embedded in polymers and a dye called crystalline purple.
Although the latter requires exposure to ultraviolet or very strong light, it has previously been shown to kill harmful bacteria alone. This causes it to produce a chemical reaction type of oxygen – called reactive oxygen, which fatally destroys the DNA and protective membranes of microorganisms.
Both types of light are not particularly useful or eye-damaging, and UV rays are harmful to humans. However, thanks to the addition of gold, when exposed to ambient light, the dye in the new coating is triggered to produce hydrogen peroxide. In laboratory tests, the surface was coated, e. coli or Staphylococcus aureus was inoculated, and then exposed to light with an average strength of only 312 lux – compared with other coatings requiring at least 3000 lux to function. Large numbers of Staphylococcus aureus were killed within six hours, while E. coli was significantly reduced after 24 hours. However, on a control surface coated with a coating containing polymers and dyes but gold- there was no reduction in bacteria.
Professor Asterios Gavrilidis, senior author of the study, said: “Gold clusters in coatings are the key to hydrogen peroxide. Given that these clusters contain only 25 gold atoms, this rare metal is required for a similar coating, which makes our coating attractive for a wide range of applications. “
The paper was published this week in the journal Nature Communications.