A comparison of continuous glucose monitors (CGMs) in diabetes management: A systematic literature review

Implantable Passive Sensors for Biomedical Applications

In recent years, implantable sensors have been extensively researched since they allow localized sensing at an area of interest (e.g., within the vicinity of a surgical site or other implant). They allow unobtrusive and potentially continuous sensing, enabling greater specificity, early warning capabilities, and thus timely clinical intervention. Wireless remote interrogation of the implanted sensor is typically achieved using radio frequency (RF), inductive coupling or ultrasound through an external device. Two categories of implantable sensors are available, namely active and passive. Active sensors offer greater capabilities, such as on-node signal and data processing, multiplexing and multimodal sensing, while also allowing lower detection limits, the possibility to encode patient sensitive information and bidirectional communication. However, they require an energy source to operate. Battery implantation, and maintenance, remains a very important constraint in many implantable applications even though energy can be provided wirelessly through the external device, in some cases. On the other hand, passive sensors offer the possibility of detection without the need for a local energy source or active electronics. They also offer significant advantages in the areas of system complexity, cost and size. In this review, implantable passive sensor technologies will be discussed along with their communication and readout schemes. Materials, detection strategies and clinical applications of passive sensors will be described. Advantages over active sensor technologies will be highlighted, as well as critical aspects related to packaging and biocompatibility.

Tuning the Localized Microenvironment near a Continuous Glucose Meter to Ensure Monitoring Accuracy and Longevity by Plasma-Induced Grafting Zwitterionic Brushes

Diabetes mellitus is a metabolic disorder that affects millions of individuals worldwide. Continuous glucose monitoring (CGM) offers a prevalent method for continuously monitoring interstitial glucose levels instead of traditional self-monitoring of blood glucose (BG), eliminating the need for finger pricking and providing only discrete data. However, challenges in accuracy persist in CGM, including substantial noise interference and tissue fluid erosion, as well as the pH fluctuations in the localized ISF microenvironment during acute inflammation periods. Herein, we reported a facile atmospheric plasma-induced grafting technique to surface functionalize a zwitterionic brush coating on the sensor, with the aim to adjust the sensor's microenvironmental chemistry. The zwitterionic brush-coated CGM (Z-coated CGM) could regulate pH values with a good glucose response in the pH range from 6.2 to 7.6 and a prolonged sensor life over the uncoated sensor. We evaluated the rat practice that the Z-coated CGM consistently outperformed the uncoated in tracking BG fluctuations, with higher correlation coefficients and significant noise reduction for both non-recalibration and recalibration. This technology holds substantial implications for subcutaneous embedded glucose monitors and facilitates CGMs in achieving independence from routine BG fingerstick calibrations.

Calibration algorithms for continuous glucose monitoring systems based on interstitial fluid sensing

Continuous glucose monitoring (CGM) is of great importance to the treatment and prevention of diabetes. As a proven commercial technology, electrochemical glucose sensor based on interstitial fluid (ISF) sensing has high sensitivity and wide detection range. Therefore, it has good promotion prospects in noninvasive or minimally-invasive CGM system. However, since there are concentration differences and time lag between glucose in plasma and ISF, the accuracy of this type of sensors are still limited. Typical calibration algorithms rely on simple linear regression which do not account for the variability of the sensitivity of sensors. To enhance the accuracy and stability of CGM based on ISF, optimization of calibration algorithm for sensors is indispensable. While there have been considerable researches on improving calibration algorithms for CGM, they have still received less attention. This article reviews the problem of typical calibration and presents the outstanding calibration algorithms in recent years. Finally, combined with existing research and emerging sensing technologies, this paper makes an outlook on the future calibration algorithms for CGM sensors.