Researchers at the Indian Institute of Science (IISc), Bengaluru, have developed a painless, needless alternative to traditional blood sugar monitoring methods using photoacoustic sensing, a laser-based technology.
Currently, people with diabetes have to test their glucose levels multiple times a day using invasive methods involving needle pricks, which can be inconvenient and increase the risk of infections. The new technique to measure glucose concentrations has been developed by the scientists from the Department of Instrumentation and Applied Physics (IAP) at IISc.
Photoacoustic sensing involves shining a laser beam on biological tissue, which absorbs the light and experiences a slight increase in temperature (less than 1°C). This leads to expansion and contraction of the tissue, generating ultrasonic sound waves that are detected by sensitive instruments. Different molecules absorb light at different wavelengths, producing unique sound wave patterns. This technique allows for accurate detection without causing damage to the tissue.
In the study, researchers used polarised light to analyse glucose concentrations. Glucose, being a chiral molecule, alters the orientation of oscillation of polarised light. The team found that this change influenced the intensity of the acoustic signal generated by the tissue. By measuring these acoustic signals, the researchers could estimate glucose concentrations with near-clinical accuracy in water and serum solutions, as well as in animal tissue samples.
“We don’t actually know why the acoustic signal changes when we alter the polarisation state, but we can establish a relationship between glucose concentration and acoustic signal intensity at a particular wavelength,” said Jaya Prakash, Assistant Professor at IAP and corresponding author of the study published in Science Advances.
The team also successfully measured glucose levels at varying depths within tissue. Since sound waves do not scatter significantly in tissue, the researchers could obtain precise readings at different layers.
A pilot study was done using the technique to track blood glucose levels in a healthy participant before and after meals over three days. While the current laser source is bulky and expensive, researchers are working on making the setup more compact and practical for clinical applications.
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“This experiment was challenging, especially in setting up the right equipment. The laser we use now generates very small nanosecond pulses, making it costly and cumbersome. Our team is already working on miniaturizing the system for real-world use,” said Swathi Padmanabhan, PhD student and first author of the study.
Beyond glucose detection, the researchers believe the technique could be used to detect other chiral molecules, including commonly used drugs like naproxen, an anti-inflammatory medication.
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