Wireless implants used to kill bacterial infection
Currently antibiotics are typically taken orally or by injection, and rely on being transported to the site of infection via the blood. Not only do the concentrations of antibiotics vary in different parts of the body, making some areas more difficult to treat but many bacterial infections are developing resistance to many antibiotics currently available. A novel approach using wireless implants to heat up the infected portion of the body appears to kill Staphylococcus aureus, which is known as MRSA (Methicillin-resistant Staphylococcus aureus) when it becomes antibiotic-resistant. The MRSA strain is one of the so-called emerging ‘super-bugs’.
Wireless implants could also help deliver drugs to an infected part of the body that is difficult for antibiotics to reach or to deliver high doses without causing side-effects to other organs or parts of the body. Tolerance to many antibiotics is also of great concern, and often leads to patients not completing the full course of treatment, which in turns help develop antibiotic-resistant strains of bacteria.
Recently, researchers at Tufts University, in collaboration with a team at the University of Illinois at Champaign-Urbana, have demonstrated a resorbable electronic implant that eliminated bacterial infection in mice by delivering heat to infected tissue when triggered by a remote wireless signal. The silk and magnesium devices then harmlessly dissolved in the test animals. The technique had previously been demonstrated only in vitro.
"This is an important demonstration step forward for the development of on-demand medical 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," said senior author Fiorenzo Omenetto, professor of biomedical engineering and Frank C. Doble professor at Tufts School of Engineering. "These wireless strategies could help manage post-surgical infection, for example, or pave the way for eventual ‘wi-fi’ drug delivery."
Researchers at Tufts University School of Engineering have demonstrated for the first time a dissolving electronic implant, made of silk and magnesium, that eliminated bacterial infection in mice by delivering heat to infected tissue when triggered by a remote wireless signal. The devices then harmlessly dissolved. In vitro studies also showed the devices could kill bacteria by releasing antibiotics. This is an important step forward for future development of on-demand medical devices that can be turned on remotely to perform a therapeutic function, such as managing post-surgical infection, and then degrade in the body. Credit: Tufts University.
Implantable medical devices typically use non-degradable materials that have limited operational lifetimes and must eventually be removed or replaced. The new wireless therapy devices are robust enough to survive mechanical handling during surgery but designed to harmlessly dissolve within minutes or weeks depending on how the silk protein was processed, noted 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.
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 "pocket" that protected the electronics and controlled its dissolution time.
Devices were implanted in vivo in S. aureus 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.
The researchers also conducted in vitro experiments in which similar remotely controlled devices released the antibiotic ampicillin to kill E. coli and S. aureus bacteria. The wireless activation of the devices was found to enhance antibiotic release without reducing antibiotic activity.
The research is published online in the Proceedings of the National Academy of Sciences Early Edition the week of November 24-28, 2014.
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