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Orthopedic implants designed to fight infections

March 9, 2015
by Richard R. Rogoski
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With the number of hip and knee replacements expected to grow among a booming senior demographic, infection caused by antibiotic-resistant bacteria is a real threat. But biomedical engineers at North Carolina State University in Raleigh may have found a way to reduce the risk of super-bug infections associated with joint replacements.

Researchers in the Department of Industrial and Systems Engineering (ISE) are developing a silver-titaniam implant with a small battery that emits a low-intensity charge to release silver ions, known to kill pathogens. Early studies showed a 99 percent decrease in bacteria growth after 24 hours and a germ-free environment after 48 hours.

"Silver has long been known for its anti-bacterial properties, but first it must ionize to be effective," said Dr. Rohan Shirwaiker, ISE assistant professor and adjunct assistant professor of biomedical engineering, in a press release. "The breakthrough was in demonstrating that a little electric current to the silver on the implant releases the ion particles, which attach to bacteria cells and either kill them or prevent them from replicating."

Work on this project at N.C. State has been ongoing since 2007, but the breakthrough study was actually part of a graduate thesis published in 2013 by Anirudh Ramnath Ganapathy, who explained that a major hurdle was to design a system that would release enough silver ions to kill the bacteria but not enough to cause toxicity to the body.