Wireless Implants Knock Out Infection Before Dissolving

Silk – it’s not just for stitches anymore, and remote controls aren’t just for TVs, either.

A team of researchers from Tufts University and the University of Illinois at Champaign-Urbana put them together to develop a resorbable electronic implant that eliminated a staphylococcus aureus infection in mice by delivering heat to infected tissue when triggered by a remote wireless signal.

The technique had previously been demonstrated only in vitro, but the silk and magnesium devices harmlessly dissolved in the test animals, according to a statement from Tufts. The research is published online in the Proceedings of the National Academy of Sciences Early Edition the week of November 24–28, 2014.

The researchers used similar remotely controlled devices to release the antibiotic ampicillin to kill E. coli and s. aureus bacteria during in vitro experiments. They found that the devices enhanced the release of the antibiotic without reducing its activity.

The wireless strategies could help manage post-surgical infection or lead to 'Wi-Fi' drug delivery, predicted two of the scientists, senior author biomedical engineering professor Fiorenzo Omenetto, and Frank C. Doble, an engineering professor at Tufts.

Implantable medical devices typically use non-degradable materials and must eventually be removed or replaced. The new wireless therapy devices can survive mechanical handling during surgery but harmlessly dissolve within minutes or weeks, depending on how the silk protein was processed, according to the paper's first author, Hu Tao, Ph.D., a former Tufts post-doctoral associate who is now on the faculty of the Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences.

Tufts engineering researchers worked with scientists from Beth Israel Deaconess Medical Center in Boston have also developed surgical plates and screws made from pure silk protein for orthopedic use. The plates and screws offer improved bone remodeling and can be absorbed by the body over time, the researchers said.

Scientists have worked for years on a variety of synthetic materials that degrade in the body in a controlled manner. Until recent years, though, only a handful of degradable materials had made their way into FDA master files. That is gradually changing, and biodegradable implants are in ever-greater demand.

To support the abdomen post-surgery, such implants need to last from six to nine months. One company, Novus Scientific, knitted two degradable polymers together to create a surgical mesh that provides such support.

The first of the two polymers, a copolymer of glycolide, lactide, and trimethylene carbonate (TMC), was engineered for fast resorption, offering mechanical strength for two months. The second, a copolymer of lactide and TMC, maintains mechanical strength for six to nine months. The mesh material completely degrades within three years.

The quick-dissolving fiber of Novus’ TIGR Matrix offers strength initially after implantation. Over time, its variable strength and elasticity assist the body in healing itself, according to the company.