A surgeon-engineer at the University of Washington is helping to design a rice-grain-sized sensor that will sit in a tear drain and monitor biomarkers.
‘We tear all the time, not just when we cry, and our tears are actually very similar to blood,’ said Tueng Shen, a UW Medicine eye surgeon and bioengineer. ‘Just like saliva and sweat, tear film carries biomarkers – proteins, molecules and other substances that indicate what is happening inside the body.’
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Shen is guiding the design of a microscopic wireless biosensor that would sit in a tear duct – a space roughly one to two millimetres across – and continuously monitor the fluid for signs of disease. The idea is funded through ARPA-H, the Advanced Research Projects Agency for Health, a US federal office focused on health innovation.
In the project’s proof-of-concept phase, the sensor will focus on two targets: inflammation and blood-sugar levels. Inflammation, measured through a molecule called IL-6, is relevant to a range of conditions, including dry eye disease. Glucose levels in tears correspond to blood-sugar levels in the body, Shen said, suggesting that the device might be a non-invasive way to track whether a chronic condition such as diabetes is well managed.
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‘We could sample the tear components minute by minute, pretty much continuously,’ Shen explained.’ That stands in contrast to blood draws, which capture the body’s information only in a single moment.
The tiny implanted sensor will be programmed to identify specific proteins or molecules. It will need to detect, power and wirelessly transmit health data for an ARPA-H directed span of at least six months. The team is exploring whether the sensor could harvest energy from the body itself.
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It’s a lot of capability to build into something the size of a grain of rice. The idea ‘pushes our engineering limits’, Shen acknowledged. ‘But I’m excited because if we can do this in a space as small as a tear duct, we can use the same technology in a much bigger space like the skin or the intestine. I see this as a broad health-monitoring platform if we can make this test work.’
The device will be manufactured using 3D-printing techniques developed by Northwestern University, one of three partner institutions on the project, alongside UW and the Massachusetts Institute of Technology.
The design is modelled on a plug commonly placed in the eye’s lower tear duct, or tear drain, as a therapy for dry eye. Because those plugs are well tolerated by patients and can remain in place for roughly six months, the research team is targeting the same lifespan for the biosensor. The insertion procedure would require no surgery and minimal anaesthesia.