Detection of target substances using ligand molecules has been widely applied for diagnosis and monitoring of diseases, basic research on infectious diseases, and detection of pollutants in the environment. In particular, antibodies are the most widely used ligands in the fields of medicine and biology. Target antigens are captured on antibody-coated plates or microbeads, and subsequently, they are detected using certain analytical methods. Fast, sensitive, and low-cost detection methods are required for early diagnosis and daily monitoring. Immunoaffinity chromatography, a typical simple diagnostic tool, can detect antigens in a short time (<10 min), but its sensitivity is low (approximately 10 × 10 11 /mL), and quantitative measurement is difficult. When more sensitive and quantitative detection is required, enzyme-linked immunosorbent assay (ELISA) is often employed.