Light could make some hospital surfaces deadly to germs

PHOENIX, Ariz. — Shining light on a new material is all it takes to make its surface toxic to germs. If used on the outside of instruments, on countertops and more, the technology might one day help hospitals limit the spread of infections, including ones that no longer respond to drugs.

Across the world, about one hospital patient in every 10 picks up a new infection while at the health care facility. That’s according to the World Health Organization. “Contaminated hospital surfaces play a key role in spreading those infections,” notes Ethel Koranteng. She’s a chemist in England at University College London.

Her team has just developed a material to make hospital surfaces self-disinfecting. Such technologies are known as “active surfaces.” That’s because they can kill germs directly. They need no additional cleansing or disinfectants.

The new material is instead based on a plastic — a flexible polymer — that can be used as a film. It might be used to cover computer keyboards, for instance. Or, the material might be molded into hard, rigid casings. These might enclose phone handles, bedrails and other easy-to-contaminate surfaces.

Other polymer-based coatings exist that resist germs. But they tend to need a spritz of water to release some germ-killing particles. The new material doesn’t. Simply turning on a room’s lights unleashes its germ-killing properties.

The idea for this is not new. Asian engineers worked on a similar sort of active surface decades ago. But that one needed a good dose of ultraviolet light to work. And that UV light can itself be hazardous to both the skin and eyes. A few years ago, two Hong Kong teens tweaked the idea to develop another UV-triggered system. It disinfects door handles (another major source of germs).

The new covering is made from polyurethane (Paa-lee-YUR-eh-thayn), a type of plastic. Embedded in it are tiny semiconductor nanobits. They’re known as quantum dots. The plastic also contains crystal violet, which is a type of purple dye. The quantum dots absorb energy from the room lighting. They then transfer some of it to the dye particles. This triggers the crystal violet to release a type of high-energy oxygen molecule. And it’s that molecule that kills germs.

In lab tests, the new material killed 99.97 percent of bacteria known as MRSA. That stands for methicillin resistant Staphylococcus aureus (Staf-uh-loh-KOK-us OR-ee-us). MRSA are immune to the germ-killing action of many antibiotics, including methicillin. The new surface was almost as good at killing a dangerous strain of E. coli. These bacteria also resists many antibiotics. What’s more, in each test, the surfaces had hosted higher levels of microbes than typically are found on hospital surfaces.

Koranteng reported her team’s success here, on April 5, at the spring national meeting of the Materials Research Society.