Versatile immunoassays based on isomagnetophoresis.

We report an isomagnetophoretic immunoassay capable of detecting an attomolar level of proteins and adjusting the dynamic range of target analytes. Here, the magnetic nanoparticles are used as labels on microbeads in sandwich-type immunoassay, detecting the amount of bound analytes by isomagnetophoretic focusing the solid-support microbeads under the magnetic susceptibility gradient and magnetic field in a microchannel. For the practical purpose, this platform was applied to detect three types of breast cancer biomarkers.