Dyes used to create light-activated antibacterial coating – that also works in the dark
By Ben Coxworth
March 28, 2014
Hospital-acquired infections are a major health threat, and have prompted the development of preventative measures incorporating things like blue light and selenium nanoparticles. One of the latest such developments is a light-activated antimicrobial surface coating made from silicone, dye and gold. For some reason, it also works in the absence of light.
Created at University College London, the coating incorporates crystal violet and methylene blue dyes, along with gold nanoparticles. When the dyes are exposed to light, the electrons in them become excited. This in turn results in the production of "highly reactive oxygen radicals," which destroy the cell walls of bacteria.
To make the material, an organic solvent was used to swell the silicone, which allowed the methylene blue and gold to diffuse throughout it. The dye- and gold-infused silicone was then dipped in a bath of crystal violet, causing a layer of that dye to bond to its surface.
In lab tests, the coating was shown to have "the most potent bactericidal effect ever observed in such a surface" when exposed even just to a regular fluorescent light bulb, killing all the bacteria placed upon it within three to six hours.
What was surprising, however, was that it also killed microbes when contaminated with them and left in the dark – it just took longer, up to 18 hours. It's reportedly the first time that a light-activated antibacterial substance has shown such good no-light performance. Exactly how it was able to do so is still being investigated.
Additionally, the coating is said to be relatively inexpensive to manufacture, and resists being worn off of surfaces when they're being cleaned. It could end up being used on items ranging from medical equipment to a hospital's door handles, keyboards or other frequently-touched objects.
Source: University College London