A Guide to Understanding Blood Glucose Monitoring Sensors

By Samudrapom DamReviewed by Susha Cheriyedath, M.Sc.Updated on Oct 23 2024

A glucose monitoring sensor is a device used to measure the concentration of glucose in the blood, providing essential data for managing diabetes. It is a crucial tool for individuals with diabetes, allowing them to monitor their blood glucose levels from home on a regular basis.

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Diabetes is a chronic condition that occurs either when the pancreas does not produce enough insulin—a hormone that helps regulate blood sugar levels—or when the body cannot effectively use the insulin it produces. Insufficient insulin production, often due to the dysfunction of beta cells in the pancreas or the presence of inactive insulin receptors, leads to elevated blood glucose levels. If not properly managed, these high glucose levels can cause serious health complications, including nerve damage, cardiovascular disease, and kidney issues.

Glucose monitors are paramount in helping patients regularly track blood glucose levels and adjust their diet, medication, and exercise routine.

Traditional methods to measure blood glucose usually involve blood analysis in the lab, which provides the most accurate representation of a patient’s blood glucose concentration. However, careful measurement techniques and regular extraction of sample blood can be physically demanding and time-consuming for the patient.¹

Components and Principles

A typical blood glucose monitoring system consists of several components, including a blood glucose meter, lancing devices, disposable test strips, and quality control solutions. Additional accessories include smartphone applications, USB cables, and log books.¹

Most conventional blood glucose monitoring systems use electrochemical biosensor technology based on amperometry. These biosensors have three key parts: sensitive recognition elements (such as enzymes or antibodies) that recognize the target glucose, a signal transducer that converts the reaction-generated current into an electric signal, and electronic systems that process this signal.^1,2

Some systems also use photometric technology, where glucose measurement relies on the interaction between glucose and enzyme reagents within a test strip. The resulting reaction is analyzed using a handheld device.^1,2

Second-Generation Monitoring Devices

Blood glucose monitoring advanced significantly in the 1980s, leading to two common techniques: the Lancet System and Continuous Glucose Monitoring Systems (CGMS).

The Lancet System

A lancet device features a needle that projects from one end (activated by pressing a button), used to prick the patient’s finger to draw a blood sample. After this, a meter strip is prepared to collect a fraction of the sample. Two main methods are used to analyze the blood: reflectance photometry and electrochemical testing.

In reflectance photometry, glucose in the blood sample interacts with a catalyzing enzyme, glucose oxidase, embedded on the test strip. The enzyme oxidizes the glucose, producing a molecule that reacts with a dye to form a complex that can be optically measured.

By shining an LED light onto this complex, the color intensity of the dye indicates the glucose concentration, with darker hues representing higher levels. The primary limitations of this method include:

• A large volume of blood sample is required (approximately 1–3µL)
• It is time-consuming, considering the blood sample processing
• Regular calibration of this technique is required to ensure the test strip delivers the most accurate result
• The optical interface may affect the results

The electrochemical method for testing blood glucose relies on a current directly proportional to glucose concentration. The blood sample is drawn between two electrodes on the test strip.

Here, glucose undergoes oxidation, transforming from beta-D-glucose to D-glucagon-1,5-lactone and then hydrolyzing into D-gluconic acid. This reaction generates an electrical current, driving electrons between the working and counter electrodes. The current generated reflects glucose concentration as the enzyme on the strip reacts with glucose. This current is then interpreted by a transducer, which records it over a 30-second interval and displays the blood glucose concentration in either mM or mg/dL.

Compared to reflectance photometry, the electrochemical method is more sensitive, requiring only 1 µL of blood and producing results in about five seconds, making it a more efficient option for blood glucose measurement.¹

One of the main drawbacks of the traditional finger-prick test is its inconvenience, as well as the increased risk of sample contamination. It also lacks the ability to monitor blood glucose levels throughout the night. The continuous glucose monitoring system (CGMS) addresses these limitations, allowing for more consistent control of blood sugar levels.

Continuous Glucose Monitoring System (CGMS)

CGMS technology works through a small implantable transmitter that detects glucose levels in the interstitial fluid—the fluid surrounding cells—and sends this data wirelessly to a monitor worn by the patient. The monitor is equipped with an alert system, notifying the patient whenever significant changes in glucose levels occur.

While CGMS does not directly measure blood glucose, it effectively estimates it through the interstitial fluid, providing frequent readings to keep the patient informed. Every few minutes, the transmitter communicates glucose data to the monitor, and if the patient uses an insulin pump, this information can be sent directly to it.

The data from the sensor is isolated, amplified, and processed into a blood glucose reading. When glucose levels reach a critical threshold, the monitor’s alarm is triggered, alerting the patient to take action.²

Revolutionizing diabetes management with reliable blood glucose monitoring without finger pricking

Advances in Blood Glucose Sensors

Non-invasive blood glucose monitoring is transforming diabetes management, offering patients a more comfortable and accessible method to track glucose levels without the need for frequent finger pricks. Recently, various innovative techniques have emerged, including optical, electrochemical, and microwave dielectric spectroscopy methods, each aiming to improve accuracy, sensitivity, and usability.³

For instance, a recent paper in Science Advances has introduced a wearable multi-sensor system for high-sensitivity, non-invasive continuous blood glucose monitoring. This system integrates several sensors: a motion sensor, environmental temperature and humidity sensor, skin conductance response (SCR) sensor, skin temperature sensor, multi-band band stop filter, and multi-band slot antenna. Together, these sensors continuously monitor various disturbance factors, creating a comprehensive glucose-sensing system.⁴

Similarly, a study published in Scientific Reports proposed a non-invasive on-body blood glucose monitoring sensor using a high-figure-of-merit surface plasmonic microwave resonator. Simulation results confirmed the effectiveness of this novel approach for continuous glucose monitoring.⁵

As these technologies continue to evolve, they promise more precise, real-time glucose tracking, which could significantly improve the quality of life for diabetic patients by enhancing comfort, reducing invasive procedures, and enabling better management of blood glucose levels.

Microelectronic Systems for Blood Glucose Monitoring

Key Market Players

The blood glucose monitoring market is driven by key players like Roche, GlucoRx, Medtronic, Dexcom, and Abbot, who continue to innovate in diabetes care.

Recently, the US Food and Drug Administration (FDA) approved Dexcom's Stelo Glucose Biosensor System, the first over-the-counter (OTC) CGM device. This device caters to adults aged 18 and older who manage diabetes without insulin, such as those on oral medications, or individuals interested in understanding how their diet and exercise affect blood sugar levels.⁶

In addition, Abbott received FDA approval for two new OTC CGM systems: Libre Rio^™ and Lingo^™. Both systems build on Abbott’s popular FreeStyle Libre^® CGM technology, expanding accessible, real-time glucose monitoring options for non-insulin users.⁷

Conclusion

Blood glucose monitoring sensors are essential tools in modern diabetes management, providing both traditional and advanced options for effective glucose tracking. With recent advances in non-invasive technologies, the future of blood glucose monitoring is promising. These innovations aim to improve accuracy, comfort, and convenience, making glucose tracking easier and more accessible for patients. As research progresses and regulatory approvals increase, these new devices have the potential to transform diabetes care—enabling more personalized management and ultimately enhancing patient health outcomes.

Advancements in Sensor Technology: What to Expect by 2030

References and Further Reading

1. Exploratory Brief on Glucose Monitoring Technologies [Online] Available at https://www.ncbi.nlm.nih.gov/books/NBK549060/ (Accessed on 23 October 2024)
2. Peng, Z. et al. (2022). Blood glucose sensors and recent advances: A review. Journal of Innovative Optical Health Sciences, 15(02), 2230003. DOI: 10.1142/S1793545822300038, https://www.worldscientific.com/doi/full/10.1142/S1793545822300038
3. Wu, J., Liu, Y., Yin, H., Guo, M. (2023). A new generation of sensors for non-invasive blood glucose monitoring. American Journal of Translational Research, 15(6), 3825. https://www.researchgate.net/publication/372308753_A_new_generation_of_sensors_for_non-invasive_blood_glucose_monitoring
4. Hanna, J. et al. (2020). Noninvasive, wearable, and tunable electromagnetic multi-sensing system for continuous glucose monitoring, mimicking vasculature anatomy. Science Advances. DOI: 10.1126/sciadv.aba5320, https://www.science.org/doi/10.1126/sciadv.aba5320
5. Soltanian, F. et al. (2023). On-body non-invasive glucose monitoring sensor based on the high figure of merit (FoM) surface plasmonic microwave resonator. Scientific Reports, 13(1), 1-13. DOI: 10.1038/s41598-023-44435-6, https://www.nature.com/articles/s41598-023-44435-6
6.  FDA Clears First Over-the-Counter Continuous Glucose Monitor [Online] Available at https://www.fda.gov/news-events/press-announcements/fda-clears-first-over-counter-continuous-glucose-monitor (Accessed on 23 October 2024)
7. Abbott Receives U.S. FDA Clearance for Two New Over-the-Counter Continuous Glucose Monitoring Systems [Online] Available at https://abbott.mediaroom.com/2024-06-10-Abbott-Receives-U-S-FDA-Clearance-for-Two-New-Over-the-Counter-Continuous-Glucose-Monitoring-Systems (Accessed on 23 October 2024)
8. Lakowicz, J.R., Geddes, C.D. (2006). Glucose Sensing. Topics in Fluorescence Spectroscopy, 11. USA: Springer Science and Business Media, Inc.
9. Gault, V., McClenaghan, N. (2009). Understanding Bioanalytical Chemistry. Principles and Applications. Analytical and Bioanalytical Chemistry, 395, 1941–1942. DOI: 10.1007/s00216-009-3215-9, https://link.springer.com/article/10.1007/s00216-009-3215-9
10.  McMahon, G. (2007). Analytical Instrumentation: A Guide to Laboratory, Portable and Miniaturized Instruments. https://analyticalscience.wiley.com/content/news-do/analytical-instrumentation-guide-laboratory-portable-and-miniaturized-instruments
11.  Zhang, X., Ju, H., Wang, J. (2008). Electrochemical Sensors, Biosensors and Their Biomedical Applications. https://www.sciencedirect.com/book/9780123737380/electrochemical-sensors-biosensors-and-their-biomedical-applications
12.  Munden, J., Foley, M. (2007). Diabetes Mellitus: A Guide to Patient Care. https://books.google.co.in/books/about/Diabetes_Mellitus.html?id=fiAclxvKblkC&redir_esc=y
13.  Porth, C. (2011). Essentials of pathophysiology: concepts of altered health states. https://books.google.co.in/books/about/Essentials_of_Pathophysiology.html?id=FFg88IaReBwC&redir_esc=y
14.  Poretsky, L. (2010). Principles of Diabetes Mellitus. 2nd Edition. https://link.springer.com/book/10.1007/978-0-387-09841-8
15.  Baura, G. (2012). Medical Device Technologies: A Systems Based Overview Using Engineering Standards. https://books.google.co.in/books/about/Medical_Device_Technologies.html?id=oVDkYP4uJwcC&redir_esc=y

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