“Measurement of blood flow is critical in many medical specialties, so a wireless biodegradable sensor could impact multiple fields, including vascular, transplant, reconstructive and cardiac surgery,” said Dr Paige Fox, assistant professor of surgery.
Monitoring the success of surgery on blood vessels is challenging, as the first sign of trouble often comes too late. By that time, the patient often needs additional surgery that carries risks similar to the original procedure. The new sensor could let doctors keep tabs on a healing vessel from afar, creating opportunities for earlier interventions.
The sensor wraps snugly around the healing vessel, where blood pulsing past pushes on the sensor’s inner surface. As the shape of that surface changes, it alters the sensor’s capacity to store electric charge, which doctors can detect remotely from a device located near the skin but outside the body. That device solicits a reading by pinging the antenna of the sensor, similar to an ID card scanner. In the future, this device could come in the form of a stick-on patch or be integrated into other technology, like a wearable device or smartphone.
The researchers first tested the sensor in an artificial setting where they pumped air through an artery-sized tube to mimic pulsing blood flow. Dr Yukitoshi Kaizawa, a former postdoctoral scholar at Stanford, also implanted the sensor around an artery in a rat. Even at such a small scale, the sensor successfully reported blood flow to the wireless reader. At this point, the researchers were only interested in detecting complete blockages, but they did see indications that future versions of the sensor could identify finer fluctuations of blood flow.
The sensor is a wireless version of technology that chemical engineer Zhenan Bao has been developing to give prostheses a delicate sense of touch.
“This one has a history,” said Bao, the K K Lee professor. “We were always interested in how we can utilise these kinds of sensors in medical applications, but it took a while to find the right fit.”
The researchers had to modify their existing sensor’s materials to make it sensitive to pulsing blood but rigid enough to hold its shape. They also had to move the antenna to a location where it would be secure, not affected by the pulsation, and redesign the capacitor so it could be placed around an artery.
“It was a very exacting project and required many rounds of experiments and redesign,” said postdoctoral scholar Levent Beker. “I’ve always been interested in medical and implant applications, and this could open up a lot of opportunities for monitoring or telemedicine for many surgical operations.”
The idea of an artery sensor began to take shape when Clementine Boutry, then a postdoctoral scholar in the Bao lab, reached out to Anaïs Legrand, then a postdoctoral scholar in the Fox lab, and connected those groups — along with the lab of James Chang, MD, the Johnson and Johnson Professor in Surgery. (Boutry is the paper’s other lead author.)
The researchers are now finding the best way to affix the sensors to the vessels and refining their sensitivity. They are also looking forward to what other ideas will come as interest grows in this interdisciplinary area.
“Using sensors to allow a patient to discover problems early on is becoming a trend for precision health,” Bao said. “It will require people from engineering, from medical school and data people to really work together, and the problems they can address are very exciting.”
