Traditionally, diabetics have relied on finger pricks or adhesive microneedles for blood sampling to measure and monitor their blood sugar levels. These methods are not only painful but can also cause itching, inflammation, and infections.
Researchers at TMOS, the Australian Research Council’s Center of Excellence for Transformative Metaoptical Systems, have taken a significant step towards eliminating this discomfort. Their RMIT University team has discovered new aspects of the infrared signature of glucose and used this information to develop a miniaturized optical sensor with a diameter of just 5 mm, which could one day be used for continuous, non-invasive glucose monitoring in diabetes treatment.
Non-invasive glucose monitoring has been a goal for almost 30 years due to its importance in pain-free monitoring. Optical techniques for glucose measurement have been reported, but they require complex optical instrumentation usually found in labs, making them unsuitable for regular patient use.
The main challenge in affordable, portable optical glucose testing has been the miniaturization and filtering of glucose signals from water absorption peaks in the near-infrared spectrum (NIR). Fundamentally, it is nearly impossible to accurately distinguish between water and glucose in the blood. Until now.
In a unique study published in Advanced Sensor Research this week, the team identified four infrared peaks in glucose that allow for selective and sensitive identification in aqueous and biological environments. The team aims to collaborate with academic and industrial partners to continue this work and conduct preclinical and clinical research that would pave the way for the development of wearable optical glucose sensors.
The team has developed a miniaturized glucose sensor based on a 1600-1700 nm wavelength band, Bluetooth-enabled, and powered by a button battery, allowing for continuous glucose monitoring. This compact sensor has demonstrated its performance in detecting glucose levels in the human body in blood plasma ranging from 50 to 400 mg/dl, with detection limits and sensitivity comparable to larger, lab-based sensors. Due to its small size, it could one day be integrated into smartwatches and other pain-free wearable health trackers.
Until now, there has been no consensus on the unique spectroscopic signature of glucose, mainly because the OH bonds targeted in near-infrared spectroscopy (NIR) for glucose detection are also abundant in water. This similarity makes it difficult to distinguish between glucose and water signals, especially in complex biological fluids and tissues. We optimized the spectroscopy setup and analyzed the transmission to identify glucose-specific peaks. Our discovery finally provides the necessary information to advance miniaturized optical glucose measurement, and we have developed a device prototype that aims to lay the foundation for a groundbreaking non-invasive glucose sensor.
Mingjie Yang, Lead Author, RMIT PhD candidate
The device prototype uses a surface-mounted light-emitting diode (SMD-LED) and circuits made of thin-layered copper-coated polyimide (Cu/PI) with a thickness of only 110 micrometers, developed using laser structuring technology. The millimeter-scale and lightweight design of this device make it significantly smaller than traditional benchtop spectrophotometers. Additionally, the flexible, patch-like design offers the future potential of direct reading as a portable device on human skin.
The device’s performance has been thoroughly evaluated using aqueous glucose solutions as well as in blood plasma. A computational analysis of light-skin interference was conducted, providing insights into how the SMD-LED penetrates the skin. Simulation results point to promising sites for future exploration of optical glucose measurement in clinical settings.
The non-invasive nature of optical glucose sensors has the potential to improve patient compliance, reduce discomfort, and decrease the risk of infections associated with invasive glucose monitoring. With the right collaborators/partners and funding, this could represent a significant shift towards continuous and pain-free glucose monitoring.
Madhu Bhaskaran, TMOS Chief Investigator
Portable sensors, like the one developed by TMOS researchers at RMIT, are part of the Center’s Meta Health Sensors flagship program, an applied research program dedicated to the development of metaoptical sensors for MedTech applications.
RMIT University has filed a patent application related to the optical glucose sensor technology developed by the team.
Source:
Australian Research Council Center of Excellence for Transformative Metaoptical Systems
Journal Reference:
Yang, M., et al. (2024). Miniaturized optical glucose sensor with 1600–1700 nm near-infrared light. Advanced Sensor Research. doi.org/10.1002/adsr.202300160.