Liquid-phase immunoassay utilizing binding reactions between magnetic markers and targets in the presence of a magnetic field

We developed a new and improved method for the liquid-phase detection of biological targets using magnetic markers. Unlike conventional studies, we performed a binding reaction between markers and targets in the presence of a magnetic field. This field acts to prevent the Brownian rotation of markers during the reaction. In this case, markers are bound to the targets with their magnetic moments (m's) aligned, which is in contrast to the conventional case where m's are randomly oriented after the reaction. As a result, we could obtain much larger signals from the bound markers without increasing the blank signal from the free markers.