Diabetics can forget the needles, it’s all about non-invasive spectroscopy

A study out of MIT suggests that measuring the chemical composition of skin could be used to monitor blood glucose levels.

Diabetics must measure their blood sugar levels multiple times a day to ensure they are not getting too high or too low. Studies have shown that more than half of patients don’t test often enough, in part because of the pain and inconvenience of the needle prick.

Published in Science Advances Researchers at MIT have discovered a potential alternative to the needle pricks, Raman spectroscopy. This is a non-invasive technique that reveals the chemical composition of tissue, such as skin, by shining near-infrared light on it. MIT scientists have now taken a vital step towards making this technique practical for patient use.

The scientists have been able to show that they can use it to directly measure glucose concentrations through the skin. Until now, glucose levels had to be calculated indirectly, based on a comparison between Raman signals and a reference measurement of blood glucose levels.

Whilst the work is still in its early stages and more work is needed to develop the technology into a user-friendly device, this advance shows that a Raman-based sensor for continuous glucose monitoring could be feasible.

Peter So, the study’s senior author and a professor of biological and mechanical engineering at MIT, explains: “Today, diabetes is a global epidemic, if there were a good method for continuous glucose monitoring, one could potentially think about developing better management of the disease.”

Underneath the skin

Raman spectroscopy can be used to identify the chemical composition of tissue by analysing how near-infrared light is scattered, or deflected, as it encounters different kinds of molecules.

MIT’s Laser Biomedical Research Center has been working on Raman-spectroscopy-based glucose sensors for more than 20 years. The near-infrared laser beam used for Raman spectroscopy can only penetrate a few millimetres into the tissue, so one key advance was to devise a way to correlate glucose measurements from the fluid that bathes skin cells, known as interstitial fluid, to blood glucose levels.

However, another key obstacle remained: The signal produced by glucose tends to get drowned out by the many other tissue components found in the skin.

Jeon Woong Kang, the study’s lead author, a research scientist at MIT and Yun Sang Park, and a research staff member at Samsung Advanced Institute of Technology explains: “When you are measuring the signal from the tissue, most of the strong signals are coming from solid components such as proteins, lipids, and collagen. Glucose is a tiny, tiny amount out of the total signal. Because of that, so far we could not actually see the glucose signal from the measured signal.”

Along with So and Kang, Sung Hyun Nam of the Samsung Advanced Institute of Technology, Seoul and have developed ways to calculate glucose levels indirectly by comparing Raman data from skin samples with glucose concentrations in blood samples taken at the same time.

However, their new approach to measuring glucose levels requires frequent calibration, and the predictions can be thrown off by the movement of the subject or changes in environmental conditions.

During their new study, the MIT team developed a new approach that allows them to see the glucose signal directly. Their technique entails shining and near-infrared light onto the skin at a 60-degree angle but collects the resulting Raman signal from a fibre perpendicular to the skin. This results in a stronger overall signal because the glucose Raman signal can be collected while the unwanted reflected signal from the skin surface is filtered out.

The researchers tested the system in pigs and found that after 10 to 15 minutes of calibration, they could get accurate glucose readings for up to an hour. They verified the readings by comparing them to glucose measurements taken from blood samples.

So explains: “This is the first time that we directly observed the glucose signal from the tissue in a transdermal way, without going through a lot of advanced computation and signal extraction.”

Development and monitoring

Although the research is well underway, further development of the technology does need to happen before the Ramen spectroscopy could be used by diabetics. The researchers now plan to work on shrinking the device, which is about the size of a desktop printer, so that it could be portable, in hopes of testing such a device on diabetic patients.

In the long term, they hope to create a wearable monitor that could offer continuous glucose measurements.