Bengaluru: Indian Institute of Science (IISc) researchers have developed a non-invasive technique to measure blood glucose levels using polarised light and sound waves, offering hope for people with diabetes who currently rely on needle pricks.
Researchers at IISc’s department of instrumentation and applied physics employed a technique called photoacoustic sensing to detect glucose concentration without piercing the skin. The method works by shining a laser beam on to tissue, causing it to heat up slightly (less than 1°C). This minimal heating creates vibrations that generate ultrasonic sound waves, which sensitive detectors can measure. Different molecules absorb varying amounts of light at different wavelengths, creating unique “fingerprints” in the emitted sound waves.
As per IISc, the team utilised the fact that glucose is a chiral molecule, meaning it has structural asymmetry that causes polarised light to rotate when interacting with it. They observed that the intensity of sound waves emitted changed when they altered the orientation of polarised light interacting with glucose in solution.
“We don’t actually know why the acoustic signal changes when we change the polarisation state. But we can establish a relationship between glucose concentration and the intensity of acoustic signal at a particular wavelength,” explained Jaya Prakash, assistant professor at IAP and corresponding author of the study published in Science Advances.
The researchers successfully estimated glucose concentration in water and serum solutions, as well as in slices of animal tissue with near-clinical accuracy. They were also able to accurately measure glucose concentration at various depths within tissue. The team conducted a pilot study tracking blood glucose concentrations of a healthy participant before and after meals over three days.
Diagnostics applications
While promising, the technology requires refinement before clinical use. “Currently, the laser source we use has to generate very small nanosecond pulses, so it is expensive and bulky. We need to make it more compact,” said Swathi Padmanabhan, PhD student and first author of the paper.
The researchers believe this technique could potentially work for any chiral molecule by changing the light wavelength. In their study, they also estimated the concentration of naproxen — a common pain medication — in an ethanol solution, suggesting broader applications in healthcare and diagnostics.