The breakthrough, based on a technique called photoacoustic sensing, can change the way glucose level is monitored.

For millions of people with diabetes, checking blood glucose levels is a painful yet daily necessity as it requires pricking the skin several times a day, which is inconvenient and poses risk of infection. However, scientists at the Indian Institute of Science (IISc) have developed a painless alternative, using light and sound instead of needles.

This breakthrough, based on a technique called photoacoustic sensing, can change the way glucose level is monitored.

‘Photoacoustic sensing’ is a method wherein a laser is beamed on to biological tissues. When the tissue absorbs the light, it heats up slightly – by less than 1 degree Celsius – causing it to expand and contract.

This tiny movement generates ultrasonic sound waves, which can be detected by specialised instruments. Since different molecules absorb light in unique ways, they create distinct “fingerprints” in the emitted sound waves, allowing scientists to identify and measure specific substances in the body – without ever needing to break the skin.

To make this technique work for glucose detection, the IISc team used polarised light – light waves vibrating in only one direction. This is similar to how sunglasses reduce glare by filtering out certain light waves. Glucose, like many biological molecules, is chiral – meaning it rotates polarised light when it interacts with it.

The researchers found that this rotation affected the intensity of the sound waves produced, revealing a way to measure glucose levels accurately.

“We do not 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 the acoustic signal at a particular wavelength,” Jaya Prakash, Assistant Professor at IISc’s Department of Instrumentation and Applied Physics, and the study’s corresponding author, explained.

As glucose concentration increases, it rotates the polarised light more, and this change is reflected in the strength of the sound waves. By analysing these signals, the researchers precisely estimated glucose levels – without needing a blood sample.

To prove the method, the team tested in different environments, starting from measuring the glucose levels in water and serum solutions, then on to slices of animal tissues, achieving near-clinical accuracy. The team could measure glucose at different depths within the tissue – a key requirement for practical medical use.

“If we know the speed of sound in the tissue, we can use the time series data to map our acoustic signals to the depth at which they are coming from,” Swathi Padmanabhan, a PhD student and first author of the study, said, adding that unlike light, which scatters inside the body, sound wave travels in a more predictable manner, allowing for clearer and more precise measurements from deeper layers of tissue.

Human trials

The researchers, following successful trials in different environments, conducted a pilot study on a healthy human participant, monitoring blood glucose level before and after meals over three days. The results showed that the technique could track glucose changes in real time.

However, researchers mentioned that scaling up the technology for widespread use comes with challenges. The current set-up requires a laser that produces extremely short nano-second pulses, which makes it bulky and expensive.

“Finding the right set-up to do this was very challenging. We need to make it more compact to put it to clinical use, and have already started work on this,” Swathi said.

The researchers believe their technique is not limited to glucose monitoring as many commonly used drugs are also chiral molecules, meaning the same method can be used to measure medication levels in the body. To test this idea, they measured the concentration of naproxen, a popular painkiller and anti-inflammatory drug, in ethanol solution, and succeeded.

source/content: newindianexpress.com (headline edited)