With 1.5 million deaths back in 2019 owing to its existence, diabetes is truly a cause for concern for both scientists and health professionals. Being a chronic disease wherein a patient is unable to produce enough insulin from the pancreas to mitigate their blood sugar levels, it presents a high risk for individuals suffering from the disease.
The deadly disease impacted 8.5% of the population above 18 years of age back in 2014 while having a global prevalence of 9.2%; premature death rates from the disease in low-, middle-, and high-class income countries were on the rise between 2010 and 2016, on the other hand.
Currently, methods of mitigating the dangerous effects of diabetes include monitoring your blood glucose levels; doing so involves either directly testing a patient’s blood or using sensors that are implanted beneath the skin of a patient. Other new ways of helping these diabetic patients are geared more towards helping those who already exhibit symptoms, like the use of hydrogels to treat diabetic skin ulcers from news just this year.
New efforts from a research team based in Pennsylvania State University are set to add another entry to the list, though: sensors placed simply atop the skin, which can detect a patient’s blood glucose levels through their sweat. Their new research was published in the journal Biosensors and Bioelectronics.
The entire assembly is based on a material called laser-induced graphene (LIG), a form of the usual atom-thick carbon sheets produced by laser irradiation of a polyimide film. In fact, an international team of researchers led by Dorothy Quiggle Career Development Professor in the Department of Engineering Science and Mechanics (ESM) Huanyu Cheng published research on this very method of LIG production just a month prior. Cheng also leads this new endeavor to develop noninvasive glucose-reading technologies.
Now, LIG by itself is insensitive to glucose, so the research team needed to deposit a glucose-sensitive material atop the LIG to get it to detect the crucial blood chemical. At the end of the day, the team chose nickel (Ni), partly due to its “robust glucose sensitivity,” according to a Penn State press release. However, nickel alone posed allergic reaction risks to some patients. To circumvent this, the nickel was alloyed with gold (Au) to lower this potential, owing to gold’s relative inertness.
The glucose sensitivity of this nickel-gold alloy also allowed Cheng and team to skip the use of enzymes, which are normally used in either more invasive, commercial glucose detection procedures or in noninvasive, experimental ones.
Said Cheng: “An enzymatic sensor has to be kept at a certain temperature and pH, and the enzyme can’t be stored in the long term. […] A nonenzymatic glucose sensor, on the other hand, is advantageous in terms of stable performance and glucose sensitivity regardless of these changes.”
The team knew that glucose concentrations in sweat are a hundred times less than that found in the blood. However, Cheng believed strong correlations between the two were present—thus, if you can read glucose levels in sweat then you get a metric for glucose levels in the blood, too.
Finally, to address the need for an alkaline solution to support the new non-enzymatic sensor, the research team decided to attach a microfluidic chamber to the LIG. A collection inlet allows the alkaline solution to get into contact with the sweat without the solution actually touching the skin.
Glucose detection proceeds as follows: This alkaline solution is the reactive component, and reacts to the glucose in a patient’s sweat; the compound this reaction produces is the one which reacts with the nickel-gold alloy, creating an electrical signal that’s detectable by the LIG—and the device connected to it. The entire initial prototype is just about the size of an American quarter coin.
The team proceeded to test the new device by attaching it to a person’s arm, who was tasked to both eat and workout just enough to sweat after eating. The new device detected glucose levels in the sweat, then corroborated its results with those obtained through regular glucose detection methods.
Cheng remains confident that the team can improve the new prototype for further studies, including usage for incremental glucose measurements and checking glucose levels after administering insulin shots. The team also hopes that their research can be expanded into detecting other functional markers in sweat in the future, possibly for the prevention, mitigation, and treatment of other diseases.
“We want to work with physicians and other health care providers to see how we can apply this technology for daily monitoring of a patient. This glucose sensor serves as a foundational example to show that we can improve the detection of biomarkers in sweat at extremely low concentrations.”
References
- Coxworth, B. (2021, October 15). Skin-adhered sensor tracks blood glucose levels via its wearer’s sweat. New Atlas. https://newatlas.com/medical/skin-sensor-blood-glucose-sweat/
- Liu, M., Wu, J., & Cheng, H. (2021). Effects of laser processing parameters on properties of laser-induced graphene by irradiating CO2 laser on polyimide. SCIENCE CHINA Technological Sciences. https://doi.org/10.1007/s11431-021-1918-8
- Stewart, G. (2021a, September 2). Graphene made with lasers for wearable health devices | Penn State University. Pennsylvania State University. https://news.psu.edu/story/667851/2021/09/02/research/graphene-made-lasers-wearable-health-devices
- Stewart, G. (2021b, October 14). Monitoring glucose levels, no needles required | Penn State University. Pennsylvania State University. https://news.psu.edu/story/672231/2021/10/14/research/monitoring-glucose-levels-no-needles-required\
- World Health Organization. (2021, April 13). Diabetes. World Health Organization. https://www.who.int/news-room/fact-sheets/detail/diabetes
- Zhu, J., Liu, S., Hu, Z., Zhang, X., Yi, N., Tang, K., Dexheimer, M. G., Lian, X., Wang, Q., Yang, J., Gray, J., & Cheng, H. (2021). Laser-induced graphene non-enzymatic glucose sensors for on-body measurements. Biosensors and Bioelectronics, 193, 113606. https://doi.org/10.1016/j.bios.2021.113606
