Although it’s known to kill bacteria, selenium has never been tried as an antibacterial coating for implanted medical devices ... until now, that is. Engineers from Rhode Island’s Brown University have applied coatings of selenium nanoparticles to pieces of polycarbonate – the material used for things like catheters and endotracheal tubes – and then exposed those samples to Staphylococcus aureus bacteria. In some cases, populations of the bacteria were subsequently reduced by up to 90 percent.

The researchers started by growing separate batches of both large and small selenium nanoparticles, then coating polycarbonate samples with them – some samples were coated with only large nanoparticles, while others were coated with only small ones. Within each of those groups, they then applied tape to some samples, then ripped it off. This was done both to test how durable the coatings were, and to see how effective less-dense coatings would perform as compared to ones that were left intact.

Next, they subjected all of the samples – along with untreated control samples – to the bacteria.

It was found that all of the treated samples, of either particle size and whether tape-tested or not, were more effective than the controls at reducing bacteria populations. This was observed at periods of 24, 48 and 72 hours after exposure. Not surprisingly, the samples that had not been tape-tested performed better than those that had. When it came to the samples that had been tape-tested, those that were coated with the smaller particles were shown to have killed more bacteria.

Selenium already occurs naturally as a nutrient in the body, so it is hoped that any nanoparticles shed by coated medical instruments would not be harmful to patients. By contrast, some other antibacterial coatings contain foreign elements such as carbon nanotubes and silver nanoparticles.

The Brown researchers now plan on testing their coating in animals, where the bacteria will have a larger source of food available, but will also be subjected to an immune response. The coating has been licensed to a spin-off company, Axena Technologies.

A paper on the research was published this week in the Journal of Biomedical Materials Research A.