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A team of engineers at Tufts University, Medford, MA, in collaboration with a team at the University of Illinois at Champaign-Urbana, demonstrated a resorbable electronic implant that eliminates bacterial infection in mice by delivering heat to infected tissue when triggered by a remote wireless signal. The devices, made of silk and magnesium, then harmlessly dissolved in the test animals.

The researchers say that this is an important step forward in the development of on-demand devices that can be turned on remotely to perform a therapeutic function in a patient and then safely disappear after their use, requiring no retrieval. The technology may also help manage post-surgical infection.

Typically, implantable devices use non-degradable materials with limited operational lifetimes and eventually must be removed or replaced. The new wireless therapy devices can survive mechanical handling during surgery but are designed to harmlessly dissolve within minutes or weeks depending on how the silk protein was processed.

Each fully dissolvable wireless heating device consisted of a serpentine resistor and a power-receiving coil made of magnesium deposited onto a silk protein layer. The magnesium heater was encapsulated in a silk envelope, which protects the electronics and controls its dissolution time.

Devices were implanted in mice with staph-infected tissue and activated by a wireless transmitter for two sets of 10-minute heat treatments. Tissue collected from the mice 24 hours after treatment showed no sign of infection, and surrounding tissues were found to be normal. Devices completely dissolved after 15 days, and magnesium levels at the implant site and surrounding areas were comparable to levels typically found in the body.

In addition, the researchers conducted in vitro experiments in which similar devices released an antibiotic to kill E. coli and S. aureus bacteria. The devices enhanced the antibiotic release without reducing antibiotic activity.

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