Magnetic particles capture fluorescent nanoparticles

Study of target capture by magnetic particles. Biotin-coated fluorescent nanoparticles (white) are captured by streptavidin-coated magnetic microparticles (black). Shown is the diffusional motion and subsequent binding of the fluorescent targets to magnetic particles lying on a substrate. Three processes can be distinguished: (1) transport of targets through the fluid volume to create encounters with the magnetic particles; (2) near-surface transport and rotation to align the binding molecules on the reactant's surfaces; and (3) the chemical reaction that firmly binds a target to a magnetic particle. Due to diffusion-limited transport of targets to the magnetic particle surface, depletion zones arise in the target concentration near the magnetic particles, limiting the capture rate. See also: A. van Reenen, A.M. de Jong, M.W.J. Prins, J. Phys. Chem. B, 117, 1210-1218 (2013).