Smart sutures send wireless status reports from wound sites

A diagram showing how the smart sutures work(Credit: Tufts University)

Flexible electronics that work with the body have been advancing quickly, doing everything from measuring our blood oxygen levels through our skin to monitoring our muscles using a tattoo. Now, a team of researchers from Tufts University has taken flexible electronics to their next logical step, embedding them in sutures that can monitor the body from the site of the stitching and broadcast their findings to a Bluetooth-enabled device.

The sutures are made from a variety of materials that are able to absorb and channel bodily fluids. "We have a suite of threads," Tuft's Sameer Sonkusale told Gizmag. "Cotton coated with carbon nanotubes, cotton coated with graphitic carbon, and threads electroplated with copper, platinum or silver." He also said that his team invented stretchable polyurethane threads covered with carbon nanotubes.

Once stitched in place in both mice and tissues samples in a lab dish, the threads were able to collect data on their surroundings including the pressure, stress and temperature at the suture site. They were also able to measure the pH and glucose levels, which can be key markers in determining how well a site is healing and whether or not infection has set in.

Sonkusale said, for example, that the electrical resistance of polyurethane threads coated with carbon nanotubes changes with strain induced on them. By tracking that resistance, it's possible to gauge how well a wound is closing and this marker was used in the study to monitor wound closure in mice. Similarly, the resistance in metallic threads changes based on temperature, so by monitoring them, it's possible to know if a wound site is extra hot, which would be a sign of infection. This component of the work is similar to previous research done with temperature-sensing sutures.

In the studies, the threads were attached to a circuit board that measured about the size of half a credit card, which was located on the skin of the mice. That board, using Bluetooth, was able to send data to a smartphone and a computer. Sonkusale, who directs Tuft's Nano Lab, told us that there is no reason why the circuit board couldn't be shrunk down in future iterations of the system and be the size of a single silicon chip.

"The ability to suture a thread-based diagnostic device intimately in a tissue or organ environment in three dimensions adds a unique feature that is not available with other flexible diagnostic platforms," said Sonkusale. "We think thread-based devices could potentially be used as smart sutures for surgical implants, smart bandages to monitor wound healing, or integrated with textile or fabric as personalized health monitors and point-of-care diagnostics."

The work of Sonkusale and his team was published online today in the journal Microsystems & Nanoengineering.

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