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Selenium Found to Control Staph Bacteria on Implant Material

Thomas Webster (Brown Univ.)

Thomas Webster (Brown Univ.)

Engineers at Brown University in Rhode Island discovered the ability of selenium nanoparticles to control the growth of staph bacteria on a type of plastic often used in medical implants. Doctoral student Qi Wang and biomedical engineering professor Thomas Webster describe their research online this week in the Journal of Biomedical Materials Research A (paid subscription required).

The study aimed to test a method for controlling the growth of bacterial biofilms on medical implants. Biofilms are colonies of bacteria considered difficult to treat and can become resistant to antibiotics.

Selenium is a mineral found naturally in food and easily tolerated by the body in small concentrations. Selenium has also been tested for various therapeutic properties.

Wang and Webster coated pieces of polycarbonate plastic, a material often used in catheters and endotracheal tubes, with selenium nanoparticles grown in larger and smaller sizes. On some of the coated polycarbonate test pieces, the researchers applied and then removed tape, which reduced the coating, a procedure designed to simulate degraded concentrations of selenium.

Using electron and atomic force microscopes, Wang and Webster measured the concentration of nanoparticles and surface areas of selenium exposed to interact with bacteria. The tape test showed that smaller nanoparticles of selenium adhered better to the polycarbonate than larger particles.

In the next stage of the tests, the researchers exposed the coated polycarbonate to cultured Staphylococcus aureus bacteria. The tests compared the ability of selenium to reduce staph bacteria growth on the polycarbonate pieces with or without selenium coatings, larger or smaller nanoparticles, and with or without tape-diminished selenium concentrations.

The results showed the selenium-coated polycarbonate pieces — with larger or smaller nanoparticles, and with or without tape-diminished concentrations — were effective in reducing staph populations after 24, 48, and 72 hours compared to the uncoated polycarbonate. The greatest reductions — 90 percent after 24 hours and 85 percent after 72 hours — in staph bacteria occurred among the full-strength nanoparticles of either size, those not degraded by tape. Among the pieces that had been subjected to tape degradation, those with the smaller nanoparticle coatings proved more effective.

Webster says the next steps will involve animal testing. In the meantime, Axena Technologies, a company in Providence, Rhode Island, has licensed the technology from Brown for commercialization.

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