A simple coating could contain the biological bullet that kills the toughest germs.

The polymer coating, developed by biomedical engineer Mary Chan of Singapore's Nanyang Technological University and her colleagues, is already being used on contact lenses by two manufacturers. When used, the coating kills 99 percent of the bacteria and fungi it comes in contact with. It could also be used for medical devices such as catheters, reducing the need for harsh disinfectants and antibiotics, which helps slow the development of resistance in the bacteria that colonize those surfaces.

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The idea came to Chan when she was trying to find a way to combat bacteria on lenses, which are often a source of infections that can damage eyes. For example, Pseudomonas aeruginosa is one bacteria that can actually digest the cornea.

Under a microscope, the structure of the polymer coating resembles a sponge. Positive charges on the surface attract bacteria like a magnetic because their surface has a negative charge. The pores in the polymer then pull the bacteria in, rupturing the organism's cellular walls and killing them. 


Chan has been working on antibacterial coatings for some time. She and a graduate student, Li Peng, built another polymer that was more liquid than solid and killed bacteria without harming human cells. That work was published in the journal Advanced Materials in March. An earlier version of Chan's polymer coating for lenses was first developed last year, with the work published in Nature Materials.

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Nanyang University's press release says that Chan's newest coating could reduce the spread of diseases in hospitals and even kitchens, where bacteria and drug-resistant bugs are a serious problem.