Binding kinetics of magnetic nanoparticles on latex beads studied by magnetorelaxometry

A system of magnetic nanoparticles (MNPs) and modified latex spheres was used serving as a model for studying binding reactions. The binding of MNPs on latex is estimated by the change of the magnetic relaxation properties of the MNP measured by a SQUID-based magnetorelaxometry measurement system. By fitting of subsequently recorded relaxation curves, the kinetics of the binding reactions, i.e. the evolution of the fraction of bound MNPs, was extracted. The signal of bound MNPs scales linearly with the concentration of latex beads. For low latex concentrations the kinetics are described by a simple aggregation model, providing information about the density and probability of bindings to the target surface.