(1 μM and 100 nM)) in the presence of S protein RBD (10 ng/mL, 100 ng/mL, 1 μg/mL,10 μg/mL). After removing the particles by magnetic separation, the fluorescence intensity of the supernatant was measured. With the concentration of RBD increased, the fluorescence intensity of the supernatant increased as well (Fig. ). This result indicates that complexation with S protein RBD caused the FAM-labelled aptamer to dissociate from the cDNA on the MBs. The capability of S protein RBD to induce separation of FAM-aptamer from MBs-cDNA was investigated in more detail.