Plasmonic nano-aperture label-free imaging (PANORAMA) of single small extracellular vesicles for cancer detection

Small extracellular vesicles (sEVs), aka exosomes, are membrane-bound nanoparticles released by cells and serve as promising biomarkers for disease diagnostics. Commonly known exosomal biomarkers include membrane proteins and intravesicular molecules such as proteins, lipids, and nucleic acids. Micro-RNA (miR), for example, has been studied extensively due to their higher stability inside exosomes and potential diagnostic value. However, the detection of single exosome from plasma remains challenging due to their small size and low abundance. Recently, our research group has developed PlAsmonic NanO-apeRture lAbel-free iMAging (PANORAMA), a technique to detect individual nanoparticles as small as 25 nm using an array of gold nanodisks on invisible substrate (AGNIS). PANORAMA enables the counting, sizing, and localization of individual sEVs in both healthy individuals and cancer patients across various stages and types by utilizing AGNIS functionalized with antibodies against exosomal surface proteins CD9, CD63, and CD81. By quantifying a portion of sEVs from 20 μL blood plasma, PANORAMA can differentiate 205 cancer patients and 106 healthy individuals with a sensitivity of 99.5% and a specificity of 97.3%.