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Magnetic immunoassay (MIA) is a novel type of diagnostic immunoassay using magnetic beads as labels in lieu of conventional enzymes (ELISA), radioisotopes (RIA) or fluorescent moieties (fluorescent immunoassays). This assay involves the specific binding of an antibody to its antigen, where a magnetic label is conjugated to one element of the pair. The presence of magnetic beads is then detected by a magnetic reader (magnetometer) which measures the magnetic field change induced by the beads. The signal measured by the magnetometer is proportional to the analyte (virus, toxin, bacteria, cardiac marker,etc.) quantity in the initial sample. == Magnetic labels == Magnetic beads are made of nanometric-sized iron oxide particles encapsulated or glued together with polymers. These magnetic beads range from 35nm up to 4.5μm. The component magnetic nanoparticles range from 5 to 50nm and exhibit a unique quality referred to as superparamagnetism in the presence of an externally applied magnetic field. First discovered by Frenchman Louis Néel, Nobel Physics Prize winner in 1970, this superparamagnetic quality has already been used for medical application in Magnetic Resonance Imaging (MRI) and in biological separations, but not yet for labeling in commercial diagnostic applications. Magnetic labels exhibit several features very well adapted for such applications: *they are not affected by reagent chemistry or photo-bleaching and are therefore stable over time, *the magnetic background in a biomolecular sample is usually insignificant, *sample turbidity or staining have no impact on magnetic properties, *magnetic beads can be manipulated remotely by magnetism. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Magnetic immunoassay」の詳細全文を読む スポンサード リンク
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