Imagine if there were a remote-control electronic device that could be implanted at an infection site, where it would treat the infection by heating or medicating the affected tissue. While it might be very effective, subsequent infections could result if surgeons went in to remove it, or even if they just left it in place. That's why scientists from Tufts University and the University of Illinois at Champaign-Urbana have developed infection-treating implants that simply dissolve into the body once they've served their purpose.
Each device consists of a silk protein substrate, on top of which a magnesium resistor and power-receiving coil are protected in a waterproof envelope made of more silk.
The scientists implanted the devices at Staphylococcus aureus infection sites in mice. An external transmitter was then used to wirelessly activate their coils, causing them to heat up. This technique was used for two sets of 10-minute heat treatments.
When the treated tissue was examined 24 hours later, there was no sign of infection, plus the surrounding tissue appeared normal. The devices proceeded to dissolve completely within 15 days, leaving no heightened magnesium levels at the implantation site. Depending on how the silk protein is processed, however, the implants could be tweaked to last anywhere from a matter of minutes up to a few weeks.
The researchers also performed in vitro experiments, in which a layer of silk containing the antibiotic ampicillin was added to the top of the devices. When they were activated, the heat caused the medication to be released from the silk, killing both E. coli and S. aureus bacteria.
"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 Tufts professor of biomedical engineering, Fiorenzo Omenetto. "These wireless strategies could help manage post-surgical infection, for example, or pave the way for eventual 'Wi-Fi' drug delivery."
A paper on the research was recently published in the journal Proceedings of the National Academy of Sciences Early Edition.