The Evolution of Next-Generation Glucose Monitoring Systems: Developments from Conventional Diagnostics to Wearable and Continuous Sensing Platforms—A Narrative Review

For the diagnosis of diabetes, glycemic control, treatment modification, and the avoidance of both acute and long-term consequences, accurate glucose monitoring is crucial. This study examines the development of glucose-monitoring systems, from traditional diagnostic tests and finger-prick electrochemical glucometers to wearable, continuous, minimally invasive, and non-invasive sensing platforms. Major invasive technologies, including enzymatic and non-enzymatic electrochemical sensors, microdialysis systems, hexokinase-based photometric assays, and field-effect transistor biosensors, are critically evaluated. The ability of minimally invasive methods to access interstitial fluid with less pain is discussed, including fluorescence probes, surface-enhanced Raman spectroscopy, and microneedle arrays. Emerging non-invasive approaches are also evaluated. These include reverse iontophoresis, optical coherence tomography, infrared and photoacoustic spectroscopy, microwave resonators, smart contact lenses, and AI-assisted wearable systems. Finally, the review identifies major barriers related to sensitivity, selectivity, calibration, biofouling, biocompatibility, physiological variability, and clinical translation. It also outlines opportunities for intelligent, painless, and patient-centered glucose monitoring.