Diabetes Forecast

Working Toward a CGM Sensor That Requires Fewer Pricks

Bing Wang, PhD
dzika_mrowka/Getty Images

Bing Wang, PhD

Occupation
Postdoctoral Researcher, University of California–Santa Barbara

Focus
Chemistry

American Diabetes Association Research Funding
Basic Science

When continuous glucose monitors (CGMs) were introduced more than 20 years ago, they represented a huge leap forward in diabetes care. The devices offered people with diabetes a way to monitor their glucose levels in near-real time, without the hassle of pricking their fingers multiple times a day to get a reading from a blood glucose meter.

Research soon showed that CGMs offered people with both type 1 and type 2 diabetes significantly improved blood glucose management. The devices were particularly helpful for kids, simplifying the daily routine of monitoring their blood glucose. Yet two decades later, only 33 percent of Americans with type 1 diabetes use a CGM, along with just 10 percent of people with type 2.

The reasons more people don’t use the devices vary. In a 2018 study published in the journal Clinical Diabetes, researchers found that 37 percent of adult CGM users stopped using them because they had to replace the sensors too often. A similar percentage said they needed to be calibrated too often, requiring frequent, painful finger sticks. Among parents of children with type 1 diabetes, almost 40 percent said their children found CGMs painful to use.

University of California–Santa Barbara chemist Bing Wang, PhD, is looking for ways to change that. He says CGM use could go up, helping people better manage their diabetes, if the devices were easier to use, less obtrusive, and required fewer finger sticks to calibrate.

With the help of a grant from the American Diabetes Association, Wang is searching for ways to tweak cutting-edge CGMs to make them ultra-stable. His hope is to find a sensor setup that won’t need to be calibrated as often, or at all.

With the standard CGM setup, that’s a challenge. Almost all CGMs on the market work the same way: When a beneath-the-skin sensor comes in contact with glucose in the body, a chemical reaction creates an electrical signal. The tiny pulse of electricity, in turn, is carried along a wire to the CGM’s transmitter and transformed into a glucose reading by a tiny computer in the monitor.

Such sensors have become so reliable that many CGMs, including Abbott’s FreeStyle Libre and the Dexcom G6, now come “factory calibrated” and typically don’t need daily finger sticks to fine-tune to the body chemistry of individual users. But because the sensitive chemicals coating the sensor don’t last, the sensors have to be replaced regularly. “Enzyme-based sensors are only effective for two weeks at most,” says Wang. Some need to be replaced as often as weekly. That can get pricey, often costing hundreds of dollars for a month’s supply even if you have insurance coverage.

That’s why Wang is interested in the potential offered by a new type of sensor. First introduced to the market in 2018 under the brand name Eversense, the so-called optical sensor is embedded in a tiny implant that’s inserted just beneath the skin. It relies on chemicals that let off a tiny flash of light when they come into contact with glucose, and it translates the intensity of the light into a glucose reading. The implant (along with its sensors) stays under the skin for as long as six months, charging and communicating via a removable transmitter.

Wang says the Eversense comes with a drawback of its own: Perhaps because of the way the light sensors work or the underlying chemistry of the sensor substances, the manufacturer still recommends that users calibrate the reader every 12 hours using finger sticks and a blood glucose meter.

When he first heard about the Eversense technology, Wang wondered whether the optical sensor could be tweaked. “How can we reduce or remove the requirement for the finger stick?” he asks. “In other words, how can we make the optical sensor more stable?”

He hopes to identify a chemical reporter that won’t need to be calibrated as often, or at all. The work is a long way from human application, but it could be an important building block for future generations of sensors. “It’s still fundamental research,” he says. “I’m changing the optical properties of the reporter and monitoring what happens.”

Wang’s work is inspired by a colleague whose daughter has type 1 diabetes, and he says easier-to-use CGMs would benefit people with type 2 as well. He’s hopeful his research will someday make a difference that people with diabetes can feel every day. “It’s important to reduce the panic around finger sticks for these kids,” he says. “If we don’t need finger sticks, we’d reduce the pain and fear associated with CGMs.”

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