They first captured tumor exosomes with CD63 aptamer-modified magnetic beads (MB), then modified silica nanoparticles (SiO2 NPs) with MUC1, HER2, EpCAM, and CEA aptamers respectively to identify specific exosomal proteins, and used N-(2-((2-aminoethyl)disulfanyl)ethyl) ferrocene carboxamide (FcNHSSNH2) as the signal molecules. Here, EPCAM is linked to neoplasm.