Microneedle Glucose Sensors Keep Monitoring Skin-Deep

For people with diabetes, glucose monitors are a valuable tool to monitor their blood sugar. The current generation of these biosensors detect glucose levels with thin, metallic filaments inserted in subcutaneous tissue, the deepest layer of the skin where most body fat is stored.

Medical technology company Biolinq is developing a new type of glucose sensor that doesn’t go deeper than the dermis, the middle layer of skin that sits above the subcutaneous tissue. The company’s “intradermal” biosensors take advantage of metabolic activity in shallower layers of skin, using an array of electrochemical microsensors to measure glucose—and other chemicals in the body—just beneath the skin’s surface.

Biolinq just concluded a pivotal clinical trial earlier this month, according to CEO Rich Yang, and the company plans to submit the device to the U.S. Food and Drug Administration for approval at the end of the year. In April, Biolinq received US $58 million in funding to support the completion of its clinical trials and subsequent submission to the FDA.

Biolinq’s glucose sensor is “the world’s first intradermal sensor that is completely autonomous,” Yang says. While other glucose monitors require a smartphone or other reader to collect and display the data, Biolinq’s includes an LED display to show when the user’s glucose is within a healthy range (indicated by a blue light) or above that range (yellow light). “We’re providing real-time feedback for people who otherwise could not see or feel their symptoms,” Yang says. (In addition to this real-time feedback, the user can also load long-term data onto a smartphone by placing it next to the sensor, like Abbott’s FreeStyle Libre, another glucose monitor.)

More than 2,000 microsensor components are etched onto each 200-millimeter silicon wafer used to manufacture the biosensors.Biolinq

Biolinq’s hope is that its approach could lead to sustainable changes in behavior on the part of the individual using the sensor. The device is intentionally placed on the upper forearm to be in plain sight, so users can receive immediate feedback without manually checking a reader. “If you drink a glass of orange juice or soda, you’ll see this go from blue to yellow,” Yang explains. That could help users better understand how their actions—such as drinking a sugary beverage—change their blood sugar and take steps to reduce that effect.

Biolinq’s device consists of an array of microneedles etched onto a silicon wafer using semiconductor manufacturing. (Other glucose sensors’ filaments are inserted with an introducer needle.) Each chip has a small 2-millimeter by 2-millimeter footprint and contains seven independent microneedles, which are coated with membranes through a process similar to electroplating in jewelry making. One challenge the industry has faced is ensuring that microsensors do not break at this small scale. The key engineering insight Biolinq introduced, Yang says, was using semiconductor manufacturing to build the biosensors. Importantly, he says, silicon “is harder than titanium and steel at this scale.”

Miniaturization allows for sensing closer to the surface of the skin, where there is a high level of metabolic activity. That makes the shallow depth ideal for monitoring glucose, as well as other important biomarkers, Yang says. Due to this versatility, combined with the use of a sensor array, the device in development can also monitor lactate, an important indicator of muscle fatigue. With the addition of a third data point, ketones (which are produced when the body burns fat), Biolinq aims to “essentially have a metabolic panel on one chip,” Yang says.

Using an array of sensors also creates redundancy, improving the reliability of the device if one sensor fails or becomes less accurate. Glucose monitors tend to drift over the course of wear, but with multiple sensors, Yang says that drift can be better managed.

One downside to the autonomous display is the drain on battery life, Yang says. The battery life limits the biosensor’s wear time to 5 days in the first-generation device. Biolinq aims to extend that to 10 days of continuous wear in its second generation, which is currently in development, by using a custom chip optimized for low-power consumption rather than off-the-shelf components.

The company has collected nearly 1 million hours of human performance data, along with comparators including commercial glucose monitors and venous blood samples, Yang says. Biolinq aims to gain FDA approval first for use in people with type 2 diabetes not using insulin and later expand to other medical indications.