Nanoparticle bandages could detect and treat infection

A "self-medicating" bandage could become a mainstay of burns units. Laced with nanoparticles, it detects harmful bacteria in a wound and responds by secreting antibiotics.

"Fifty per cent of all people who die as a result of burn injuries do so as a direct consequence of infection, which is why this research is so important," says Toby Jenkins from the University of Bath, UK, who is developing the bandage with an international team of researchers.

Harmful bacteria cause infections by attacking cells with toxins that dissolve the cell membrane. "Friendly" bacteria, which help the body to function, don't carry this toxic arsenal. This simple difference is the big idea behind Jenkins's smart bandages.

He wondered if pathogenic bacteria could be made the agents of their own destruction by using their toxins to rupture vesicles containing an antimicrobial agent. If this worked, the vesicles could be attached to bandages that would release antibiotics only if a wound became infected.

"This reduces the risk of the evolution of new antibiotic-resistant superbugs such as MRSA," says Jenkins. The vesicles would also contain a dye, so the dressing would change colour if it came in contact with dangerous bacteria, alerting doctors of an infection.

Tested on superbugs

To test the idea, Jenkins attached small capsules containing an antimicrobial chemical called sodium azide to a fabric and exposed them to two of the most common bacteria responsible for infections in hospitals: Staphylococcus aureus and Pseudomonas aeruginosa. He also tested it against a harmless strain of Escherichia coli that doesn't secrete toxins.

As expected, when subjected to the toxic bacteria, the capsules bust, releasing their antimicrobial payload, and the amount of bacteria quickly diminished. There was also a slight decrease of E. coli, which the researchers attribute to a small amount of capsule leakage.

Currently bandages have to be removed if an infection is suspected, which can cause injury to the patient and can slow healing.

"This is an exciting, promising and novel idea. However, a lot of work will be necessary to show that its early promise can translate into clinical benefit," says Jim Gray, a microbiologist at Birmingham Children's Hospital, UK. Jenkins says one of the biggest challenges will be ensuring that vesicles are stable enough for the dressings to be stored without losing effectiveness. He expects it will take around five years to bring the technology to clinical use.

Gray thinks the technology might also be useful in external dressings that are used to fix in place central venous catheters and other medical devices that are inserted into the body. "These devices are an important source of bloodstream infection. Early identification and treatment of infections of the skin at the site of entry of these devices could reduce the risk of bloodstream infection developing," he says.