The abovementioned results demonstrate the effectiveness of the proposed VIF platform in detecting NPs using affinity capture beads. However, its viability in diagnostic applications is still unclear, because the affinity between avidin and biotin is higher than that of other biological affinity-capture systems. Thus, we further examined the performance of the proposed system in detecting EVs, important biological NPs present in body fluids. We used EVs derived from bovine milk as the target NPs. To detect the EVs, Tim-4 conjugated magnetic beads, which exhibit an affinity for phosphatidylserine on the EV membrane in a calcium-ion-dependent manner, were used. The diameter of the magnetic capture beads provided by a manufacturer was 3 µm, and that of EV measured with an imaging analyzer was 219 ± 75 nm (see Figure , Supporting Information).