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Figure 2. EV purification and detection using SPRi. (A) EVs were purified using ExoQuick®, and the extent of purification was assessed by TEM and western blotting, compared to ultracentrifugation; (B) Two spots were prepared for each ligand, and the average of the maximum values from the kinetic curves was used as the quantitative measure of the ligand; (C) Kinetic curve for tetraspanin family proteins (CD63, CD9, and CD81), blank and isotype control, and images of each spot obtained from measuring healthy human serum with SPRi. Reagent control (100-fold diluted ExoQuick) was used to confirm nonspecific reactions of the reagents. Evs: Extracellular vesicles; TEM: transmission electron microscopy; SPRi: surface plasmon resonance imaging.