Development of an optimized dome-shaped magnet for rapid magnetic immunostaining

Magnetic immunostaining is a technique used to accelerate the antigen-antibody immunoreaction by increasing the local density of antibody on the surface of a tissue specimen using a magnetic field. The high density of antibody is achieved by applying a magnetic force to antibody-labeled ferrite beads toward the specimen. A technical challenge of using conventional magnets for this technique has been the inhomogeneous accumulation of magnetic beads on the specimen in accordance with the distribution of the magnetic field. Thus, in this study, a dome-shaped magnet that generated a strong and uniform magnetic force distribution was proposed and demonstrated. Numerical analysis was used to optimize the shape of the magnet. Analysis of the motion of magnetic beads showed that the accumulation of beads on the sample was complete within one minute and that the resulting homogeneity was sufficient for rapid and accurate immunostaining. Finally, experiments showed that the homogeneity of the bead distribution was improved by the use of a prototype dome-shaped magnet compared to conventional cylindrical magnets.