Microfluidic nano-plasmonic imaging platform for purification- and label-free single small extracellular vesicle characterization.

Tumor-derived circulating small extracellular vesicles (sEVs) are a promising class of non-invasive biomarkers for disease diagnosis. However, their quantitative detection remains challenging due to their small size and the complexity of blood plasma. Therefore, sample preparation, such as purification and fluorescence labeling, is required. This study presents a purification-free approach using a microfluidic chip integrated with PlAsmonic NanO-apeRture lAbel-free iMAging (PANORAMA) for label-free single sEV characterization in plasma. CD63, CD9, and CD81 antibodies, specific for most sEVs surface antigens, are functionalized on arrayed gold nanodisks on invisible substrates (AGNIS) for selective capture. The automated microfluidic platform minimizes operational errors and biases and enables precise control of flow rates, directions, media volume, and composition for optimization. This platform requires only 20 µL of plasma, and the analysis is completed within 60 minutes. This platform shows great potential as a sensitive and effective tool for detecting and characterizing circulating sEVs without purification or labeling.