Researchers at the University of California, Berkeley have developed an ultrasound-powered implantable sensor that can measure oxygen levels in tissues deep within the body and transmit these data to an external device. The technology could be useful in monitoring transplant viability or oxygen exposure in preterm infants. It also has potential to be adapted to measure other biochemical markers, such as carbon dioxide concentrations or pH levels.
Oxygen is crucial for living tissues, and poor oxygenation leads to cell death. This process forms the basis for various pathological phenomena, but clinicians can struggle to measure tissue oxygenation, at least in tissues that aren’t near the surface of the body. Current methods to assess tissue oxygenation involve using infrared light, but this can only penetrate a few centimeters at most.
“It’s very difficult to measure things deep inside the body,” said Michel Maharbiz, a researcher involved in the study, in a Berkeley announcement. “The device demonstrates how, using ultrasound technology coupled with very clever integrated circuit design, you can create sophisticated implants that go very deep into tissue to take data from organs.”
The new implants are powered using ultrasonic waves, which can travel long distances through the body. An external probe transmits ultrasonic vibrations through the body, which power the tiny device implanted inside. Data is transmitted back by reflecting these ultrasonic waves while embedding in them data packets on tissue oxygenation levels. This technique allows for bidirectional data exchange with devices deep inside the body.
Oxygen sensing occurs through an on-board LED and optical detector within the impalnt. The device itself is tiny, and the researchers describe it as smaller than a ladybug. So far, they have tested the device by monitoring the oxygen levels in muscle in live sheep.
“One potential application of this device is to monitor organ transplants, because in the months after organ transplantation, vascular complications can occur, and these complications may lead to graft dysfunction,” said Soner Sonmezoglu, another researcher involved in the project. “It could be used to measure tumor hypoxia, as well, which can help doctors guide cancer radiation therapy.”
An important potential application of the new technology involves using it to help manage oxygen levels in premature infants. “In premature infants, for example, we frequently need to give supplemental oxygen but don’t have a reliable tissue readout of oxygen concentration,” said Emin Maltepe, a third researcher involves in the project. “Further miniaturized versions of this device could help us better manage oxygen exposure in our preterm infants in the intensive care nursery setting and help minimize some of the negative consequences of excessive oxygen exposure, such as retinopathy of prematurity or chronic lung disease.”
Study in Nature Biotechnology: Monitoring deep-tissue oxygenation with a millimeter-scale ultrasonic implant