Magnetic beads are made of nano-sized iron oxide particles encapsulated or bonded with polymers. These magnetic beads range in size from 35 nm to 4.5 μ m, and the magnetic nanoparticles range in size from 5 nm to 50 nm. They exhibit a unique property called superparamagnetism in the presence of an external magnetic field. Magnetic immunoassay ((MIA)) is a new diagnostic immunoassay method, which uses magnetic beads as labeling instead of traditional enzyme (ELISA), radioisotope (RIA) or fluorescence part (fluorescence immunoassay) to detect specific analytes. MIA involves the specific binding of an antibody to its antigen, in which a magnetic tag is connected to an element in the antibody pair.