Non-invasive glucose monitoring will allow diabetics to measure blood glucose without having to draw blood. Shutterstock | Syda Productions
Diabetes is a disease involving chronically high sugar levels in the blood, and around 422 million people across the world are suffering from this disease . Due to its widespread presence across the globe and its colossal impact on health , Type-2 diabetes has been known as the “black death” of the 21st century.
Loss of consciousness, seizures and even death can occur if the blood glucose level is very low. The complications that can occur as a result of very high blood glucose level include infections, kidney damage and cardiovascular disease .
Standard glucose monitoring procedures involve collecting a drop of blood by stabbing the finger using a needle, or invasively. This process not only causes pain to the patient, but is also expensive due to a new test strip being needed for each measurement. Moreover, these measurements have to be carried out on patients several times a day .
Since standard glucose monitoring procedures are both painful and costly, extensive efforts have been taken to develop non-invasive (and pain-free) methods that do not require the finger to be pricked. Ideally, these methods should also not require consumable items. This would be more convenient for diabetics and would reduce costs for treatment providers.
Although non-invasive techniques have been studied for several decades, no true solution has been reached so far, and as a result, conventional, and invasive, blood glucose level monitoring methods remain the standard .
Non-Invasive Methods of Blood Glucose Monitoring
The past few years have seen the development of several non-invasive methods, including transdermal techniques such as reverse iontophoresis and skin impedance spectroscopy, and optical methods like optical coherence tomography and Raman spectroscopy.
However, these techniques have their own drawbacks that have so far stopped them from becoming a standard blood glucose level monitoring method.
Mid-infrared (mid-IR) spectroscopy is a promising method for measuring blood glucose level as it is capable of identifying the highly specific vibrational modes or ‘chemical fingerprints’ of glucose molecules with very high sensitivity. Reports are, in fact, already available discussing the use of the mid-IR spectroscopy for quantitative analysis of glucose molecules in dialysis fluid, blood and blood plasma [8-9].
The right mid-IR laser needs to be used in mid-IR spectroscopy in order to make the technique a viable option. The following are the key qualities to be possessed by an ideal mid-IR laser:
- High tuning speed for rapid data acquisition
- Ability to tune with good power across the region of absorption of glucose molecules in the mid-IR spectrum
However, to design a laser with a high tuning speed, one has to compromise in other areas. For sensitive (high signal-to-noise ratio) detection of glucose molecules, the quality of the light from the laser must not be compromised for the tuning speed. The laser should possess high beam quality and high spectral repeatability (low variability in wavelength and spectral content of the laser output) to enable highly consistent and accurate measurements.
Case Study: Using mid-IR Spectroscopy to Monitor Blood Glucose Concentration
In a study, glucose level in the interstitial layer of the human skin was determined using mid-IR spectroscopy . Here, the absorption process was detected using a combination of photoacoustic spectroscopy in the ultrasound region and the high pulse energy emitted by an external cavity quantum cascade laser that can be tuned across the infrared glucose fingerprint region. Using this combination, the authors quantitatively measured glucose concentrations in the range from <50 mg/dL to >300 mg/dL, which is the relevant range for monitoring glucose level in diabetics. Since the laser intensity applied was below 1 mW/mm2, the patient’s skin was not hurt or altered.
According to the authors, since the measurements performed in this study were representative of the level of blood glucose, their method of using mid-IR photoacoustic spectroscopy holds potential for monitoring the levels of blood glucose in diabetics conveniently, without causing any pain to the patient . Hence, it can be concluded that this technique represents a highly potential non-invasive glucose monitoring method.
Next-Generation Tunable Lasers for Non-Invasive Glucose Monitoring
Daylight Solutions’ new Hedgehog™ laser system delivers the high-quality laser light and the high-speed tuning essential 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.
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 World Health Organization, Global Report on Diabetes, 2016, WHO Press
 Michael Greger, How Not To Die: Discover the Foods Scientifically Proven to Prevent and Reverse Disease, 2016, Macmillan
 Centers for Disease Control and Prevention. Deaths: Final Data for 2013, table 10. Number of Deaths from 113 Selected Causes. National Vital Statistics Report, 2016; 64 (2)
 American Association of Pharmaceutical Scientists, Noninvasive Blood Glucose Monitoring Device for People with Diabetes in Development, 2016, AAAS
 Pleitez et al. In Vivo Noninvasive Monitoring of Glucose Concentration in Human Epidermis by Mid-Infrared Pulsed Photoacoustic Spectroscopy, Anal. Chem. 2013, 85, 1013−1020
 Liakat et al. In Vitro Measurements of Physiological Glucose Concentrations in Biological Fluids using Mid-Infrared Light, Biomed. Opt. Express 2013, 4, 1083
 Ciudin et al. Non-Invasive Methods of Glucose Measurement: Current Status and Future Perspectives, Diabetes Rev. 2012, 8, 48−54.
 Damm et al. Continuous Reagent-Free Bed-Side Monitoring of Glucose in Biofluids using Infrared Spectrometry and Micro-Dialysis, Vib. Spectrosc. 2007, 43, 184−192.
 Heise et al. Bedside Monitoring of Subcutaneous Interstitial Glucose in Healthy Individuals Using Microdialysis and Infrared Spectrometry J. Biomed. Opt. 2007, 12, 024004-1−024004-12
This information has been sourced, reviewed and adapted from materials provided by Daylight Solutions Inc.
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