Non-Invasive Glucose Monitoring

Non-Invasive Blood Glucose Monitoring using Mid-IR Spectroscopy

422 million people worldwide suffer from diabetes1, a disease characterized by chronically elevated levels of sugar in the blood. Type-2 diabetes has been called the “black death” of the 21st century, due to its massive spread globally and its devastating impact on health2.

If blood glucose is too low, for example, seizures, loss of consciousness, and even death can result. If too high, complications can include infections, cardiovascular disease, and kidney damage3.

Standard glucose monitoring procedures, where a drop of blood is obtained by pricking the finger with a needle, are invasive. This is not only painful for the patient, but also costly, as each measurement needs a new test strip. Additionally, the patient must carry out these measurements several times a day4.

Because of the pain and cost involved, considerable effort has been made to develop non-invasive (and pain-free) methods that don’t involve stabbing the finger. Ideally, these methods should also not require consumable items. This would be more convenient for diabetics and would reduce costs for treatment providers. While non-invasive techniques have been studied for decades, no true solution has been reached so far, and traditional, and invasive, methods of monitoring blood glucose levels remain the standard.

Non-Invasive Methods of Blood Glucose Monitoring

Several non-invasive methods have been developed over the last few years. These include transdermal techniques such as skin impedance spectroscopy and reverse iontophoresis, as well as optical methods like Raman spectroscopy and optical coherence tomography. These techniques, however, all have weaknesses that have so far prevented them from becoming a standard method of measuring blood glucose.

One promising technique for monitoring blood glucose is mid-infrared (mid-IR) spectroscopy. The advantage of this technique is that it can identify the highly specific vibrational modes or ‘chemical fingerprints’ of glucose molecules with high sensitivity thereby enabling quantitation of glucose levels in a complex biofluid background.

For mid-IR spectroscopy to become a viable option, the right mid-IR laser source is required. The ideal mid-IR laser should have high spectral brightness and tune across the region of the mid-IR spectrum where glucose molecules strongly absorb. Furthermore, it should exhibit fast tuning speeds for real-time data acquisition, low noise, and superb wavelength accuracy and scan-to-scan repeatability. Designing a laser for high tuning speeds, however, can potentially compromise other areas of performance. To enable sensitive (high signal-to-noise ratio) detection of glucose molecules, tuning speed must not sacrifice the quality of the light emitted by the laser. To ensure highly consistent and accurate measurements the laser should, for example, have high spectral repeatability (low variability in wavelength and spectral content of the laser output) and superb beam quality.

Using Mid-IR Spectroscopy to Monitor Blood Glucose Concentration

A recent publication from researchers at Goethe University Frankfurt demonstrates how mid-IR spectroscopy can be used to determine glucose concentration in the interstitial layer of the human skin5.

The authors of this study used photothermal spectroscopy in the ultrasound region to detect the absorption process. They combined this with high pulse energy from an external cavity quantum cascade laser that was tunable across the infrared glucose fingerprint region. This combination allowed a quantitative measurement for glucose concentrations in the range from >50 mg/dL to 300 mg/dL. This is the relevant range for glucose monitoring in diabetics. The intensity of the laser light delivered to the patient’s skin was below 1 mW/mm2, which is well below the threshold for sensation or skin damage.

The authors comment that, because their measurements were representative of the blood glucose level, their method of using mid-IR photoacoustic spectroscopy could be used to monitor blood glucose levels in diabetics. This offers a method that is pain-free and convenient for the patient. In summary – this technique represents a highly promising non-invasive method of glucose monitoring.

Learn how DiaMonTech is leveraging tunable quantum cascade laser technology to pioneer the future of non-invasive glucose monitoring.

Next-Generation Tunable Lasers for Non-Invasive Glucose Monitoring

The Hedgehog™ tunable mid-IR laser system from Daylight Solutions delivers the high-speed tuning and high-quality laser light needed for non-invasive glucose monitoring techniques. For the first time, fast and broad tuning, Continuous Wave (CW) or pulsed output, high spectral repeatability, high power and power stability, and high beam quality are available from a compact, robust mid-IR laser. Learn how Hedgehog’s unique blend of features and performance can help progress the development of non-invasive glucose monitoring.

1 World Health Organization – Global Reports on Diabetes 2016
2 Michael Greger – How Not To Die: Discover the Foods Scientifically Proven to Prevent and Reverse Disease, 2016
3 Mayo Clinic – Diabetic Hypoglycemia
4 TheDiabetesCouncil.Com – Everything You Need To Know About Diabetes Test Strips 2020
5 Pleitez, M. A., et al. – In Vivo Noninvasive Monitoring of Glucose Concentration in Human Epidermis by Mid-Infrared Pulsed Photoacoustic Spectroscopy – Analytical Chemistry 2012

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