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.
antibiotic A germ-killing substance, usually prescribed as a medicine (or sometimes as a feed additive to promote the growth of livestock). It does not work against viruses.
bacteria (singular: bacterium) Single-celled organisms. These dwell nearly everywhere on Earth, from the bottom of the sea to inside other living organisms (such as plants and animals).
casing (n.) Some structure that encloses the potentially fragile working parts of a device, such as a cellular phone. It affords those internal parts protection by fully covering, or encasing, them. (in food science) The outer skin or material used to hold — or encase — the meat and other ingredients used to make a sausage.
E. coli (short for Escherichia coli) A common bacterium that researchers often harness to study genetics. Some naturally occurring strains of this microbe cause disease, but many others do not.
infection A disease that can spread from one organism to another. It’s usually caused by some type of germ.
microbe Short for microorganism. A living thing that is too small to see with the unaided eye, including bacteria, some fungi and many other organisms such as amoebas. Most consist of a single cell.
molecule An electrically neutral group of atoms that represents the smallest possible amount of a chemical compound. Molecules can be made of single types of atoms or of different types. For example, the oxygen in the air is made of two oxygen atoms (O2), but water is made of two hydrogen atoms and one oxygen atom (H2O).
MRSA An abbreviation for methicillin-resistant Staphylococcus aureus. Methicillin is a widely used antibiotic. And S. aureus is a bacterium that can cause boils, food poisoning, toxic-shock syndrome and more. These bacteria sicken (and sometimes kill) by releasing potent natural poisons into the body, called toxins.
nanoparticle A small particle with dimensions measured in billionths of a meter.
oxygen A gas that makes up about 21 percent of Earth's atmosphere. All animals and many microorganisms need oxygen to fuel their growth (and metabolism).
particle A minute amount of something.
polymer A substance made from long chains of repeating groups of atoms. Manufactured polymers include nylon, polyvinyl chloride (better known as PVC) and many types of plastics. Natural polymers include rubber, silk and cellulose (found in plants and used to make paper, for example).
polyurethane An often elastic plastic made from crosslinked chains of molecules.
quantum dot A nanoparticle of semiconducting material (meaning one with dimensions measured on the scale of billionths of a meter). It is inserted into cells, organisms or electronic materials, where it can be used as a label (tag) or to turn trigger some function (such as the production of sterilizing chemicals).
semiconductor A material that sometimes conducts electricity. Semiconductors are important parts of computer chips and certain new electronic technologies, such as light-emitting diodes.
Staphylococcus aureus (also known as staph) A species of bacteria that is responsible for a number of serious human infections. It can cause surface abscesses, or boils. If it gets into the bloodstream, where it can be carried throughout the body, it may also cause pneumonia and infections of the joints or bones.
strain (in biology) Organisms that belong to the same species that share some small but definable characteristics. For example, biologists breed certain strains of mice that may have a particular susceptibility to disease. Certain bacteria or viruses may develop one or more mutations that turn them into a strain that is immune to the ordinarily lethal effect of one or more drugs.
ultraviolet light (abbreviated UV light) A type of electromagnetic radiation with a wavelength from 10 nanometers to 380 nanometers. The wavelengths are shorter than that of visible light but longer than X-rays.
World Health Organization An agency of the United Nations, established in 1948, to promote health and to control communicable diseases. It is based in Geneva, Switzerland. The United Nations relies on the WHO for providing international leadership on global health matters. This organization also helps shape the research agenda for health issues and sets standards for pollutants and other things that could pose a risk to health. WHO also regularly reviews data to set policies for maintaining health and a healthy environment.