A noninvasive method for measuring blood glucose levels, developed at MIT, could save diabetes patients from having to prick their fingers several times a day.

The MIT team used Raman spectroscopy — a technique that reveals the chemical composition of tissues by shining near-infrared or visible light on them — to develop a shoebox-sized device that can measure blood glucose levels without any needles, reports Anne Trafton in MIT News.

In tests in a healthy volunteer, the researchers found that the measurements from their device were similar to those obtained by commercial continuous glucose monitoring sensors that require a wire to be implanted under the skin. While the device presented in this study is too large to be used as a wearable sensor, the researchers have since developed a wearable version that they are now testing in a small clinical study.

“For a long time, the finger stick has been the standard method for measuring blood sugar, but nobody wants to prick their finger every day, multiple times a day. Naturally, many diabetic patients are under-testing their blood glucose levels, which can cause serious complications,” says Jeon Woong Kang, an MIT research scientist and the senior author of the study. “If we can make a noninvasive glucose monitor with high accuracy, then almost everyone with diabetes will benefit from this new technology.”

MIT postdoc Arianna Bresci is the lead author of the new study, which appears today in the journal Analytical Chemistry.

Noninvasive glucose measurement

While most diabetes patients measure their blood glucose levels by drawing blood and testing it with a glucometer, some use wearable monitors, which have a sensor that is inserted just under the skin. These sensors provide continuous glucose measurements from the interstitial fluid, but they can cause skin irritation and they need to be replaced every 10 to 15 days.

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In hopes of creating wearable glucose monitors that would be more comfortable for patients, researchers in MIT’s LBRC have been pursuing noninvasive sensors based on Raman spectroscopy. This type of spectroscopy reveals the chemical composition of tissue or cells by analyzing how near-infrared light is scattered, or deflected, as it encounters different kinds of molecules.

Typically, a Raman spectrum may contain about 1,000 bands. However, the MIT team found that they could determine blood glucose levels by measuring just three bands — one from the glucose plus two background measurements. This approach allowed the researchers to reduce the amount and cost of equipment needed, allowing them to perform the measurement with a cost-effective device about the size of a shoebox.

“By refraining from acquiring the whole spectrum, which has a lot of redundant information, we go down to three bands selected from about 1,000,” Bresci says. “With this new approach, we can change the components commonly used in Raman-based devices, and save space, time, and cost.”

Toward a wearable sensor

In a clinical study performed at the MIT Center for Clinical Translation Research (CCTR), the researchers used the new device to take readings from a healthy volunteer over a four-hour period. As the subject rested their arm on top of the device, a near-infrared beam shone through a small glass window onto the skin to perform the measurement.

Each measurement takes a little more than 30 seconds, and the researchers took a new reading every five minutes.

During the study, the subject consumed two 75-gram glucose drinks, allowing the researchers to monitor significant changes in blood glucose concentration. They found that the Raman-based device showed accuracy levels similar to those of two commercially available, invasive glucose monitors worn by the subject.

Since finishing that study, the researchers have developed a smaller prototype, about the size of a cellphone, that they’re currently testing at the MIT CCTR as a wearable monitor in healthy and prediabetic volunteers. Next year, they plan to run a larger study working with a local hospital, which will include people with diabetes.

The researchers are also working on making the device even smaller, about the size of a watch. Additionally, they are exploring ways to ensure that the device can obtain accurate readings from people with different skin tones.

The research was funded by the National Institutes of Health, the Korean Technology and Information Promotion Agency for SMEs, and Apollon Inc.