Applications of metal enhanced fluorescence for the detection and quantification of extracellular vesicles

Early detection of diseases significantly improves patient outcomes, yet many biomarkers remain at ultra-low concentrations in body fluids during the initial stages, posing challenges for conventional diagnostic techniques. Extracellular vesicles (EVs) have emerged as promising non-invasive biomarkers due to their presence in body fluids such as blood, saliva and urine, and because their molecular cargo reflects their cells of origin. However, sensitive and accurate detection of disease related EVs is challenging because of their low concentrations and nanoscale size. Metal enhanced fluorescence (MEF) has recently been applied to overcome these limitations by amplifying the fluorescent signal of labeled EVs through localized surface plasmon resonances of metallic nanostructures. This amplification enables the detection and quantification of EV-associated biomarkers with improved sensitivity, offering potential for earlier disease diagnosis. However, to date, few reviews have focused specifically on MEF-based applications for the detection and quantification of EVs and their molecular cargo. This review examines recent advances in MEF-based platforms for EV analysis, including nanohole arrays, metal nano islands and nanoarrays, gold nanoparticles in three-dimensional matrices, metal-organic frameworks and other plasmonic approaches. While current reviews have discussed the use of MEF biosensing application, this article specifically focuses on MEF- based EV detection highlighting the design principles, optical properties, advantages, and limitations of these platforms. Collectively, MEF offers a powerful strategy to enhance EV detection, bridging the gap between experimental analysis and clinical application.