Material that kills deadly bacteria even in the dark

In a breakthrough, researchers at University College London (UCL) have developed a new antibacterial material which has potential for cutting hospital-acquired infections.

The combination of two simple dyes with nanoscopic particles of gold is deadly to bacteria when activated by light - even under modest indoor lighting.

In a first for this type of substance, it also shows impressive antibacterial properties in total darkness.

Hospital-acquired infections are a major issue for modern medicine. It is difficult to eliminate these infections unless you can make the hospital environment more hostile to microbes.

Surfaces such as door handles, medical equipment, keyboards, pens and so on are an easy route for germs to spread, even onto freshly-cleaned hands.

"There are certain dyes that are known to be harmful to bacteria when subjected to bright light," explained Ivan Parkin, head of UCL chemistry.

The light excites electrons in them, promoting the dye molecules to an excited triplet state and ultimately produces highly reactive oxygen radicals that damage bacteria cell walls.

"Our project tested new combinations of these dyes along with gold nanoparticles, and simplified ways of treating surfaces which could make the technology easier and cheaper to roll out," Sacha Noimark from UCL added.

In lab tests, despite contaminating the surface with far more bacteria than you would ever see in a hospital setting, the entire sample under light was dead in three to six hours depending on the type of bacteria, Noimark noted.

The bigger surprise was the sample which was left in the dark.

This is the first time a light-activated antimicrobial surface has had any kind of effect in the dark.

"That sample too showed significant reductions in bacterial load, albeit over longer timescales of about three to 18 hours," the researchers said in the study published in the journal Chemical Science.