Heating ability modulation by clustering of magnetic particles for precision therapy and diagnosis

Magnetic and thermal properties of clustered magnetite nanoparticles submitted to a high-frequency magnetic field is studied by means of rate equations. A simple model of large particle clusters (containing more than one hundred individual particles) is introduced. Dipolar interactions among clustered particles markedly modify shape and area of the hysteresis loops in a way critically dependent on particle size and cluster dimensions, thereby modulating the power released as heat to a host medium. For monodisperse and polydisperse systems, particle clustering can lead to either a significant enhancement or a definite reduction of the released power; in particular cases the same particles can produce opposite effects in dependence of the dimensions of the clusters. Modulation by clustering of the heating ability of magnetic nanoparticles has impact on applications requiring optimization and accurate control of temperature in the host medium, such as magnetic hyperthermia for precision therapy or fluid flow management, and advanced diagnostics involving magnetic tracers. (paper)