Assessing the impact of magnetic nanoparticle assemblies on magnetic hyperthermia performance: A predictive study

Abstract

Background and objective: Magnetic hyperthermia-based therapies depend on heating performances of magnetic nanoparticles (MNP). Beyond specific MNP properties, dipole-dipole interactions resulting from the formation of MNP assemblies have a pivotal influence on heating performance. There is, however, limited understanding of the range of attributable negative and positive effects.

Methods: Numerical simulations were used to unravel the effect of various spherical, elongated assemblies as well as MNP chains on heating performance. An advancing front assembly generating method was combined with a stochastic Langevin simulation. Experimental values of a hyperthermia application to destroy hollow organ tumours with heatable stent fibres were used to validate simulation results.

Results: Limited impact of assembly size on the heating performance was observed, whereas assembly geometry was crucial. Spherical assemblies lead to a decrease in specific loss power while elongated assemblies and chains yielded up to eightfold increase compared to randomly dispersed MNP. The heating performance of elongated assemblies and chains was dependent on their major-minor axes ratios, excitation field amplitude and assembly orientation relative to the field direction. The simulations unravelled that chains dominated the heating of stent fibres.

Conclusions: The simulation is a valuable and versatile tool for the optimization of heating output of all sorts of MNP, which undergo structural changes in interaction with artificial and biological surroundings. This capability is demonstrated for fibre-based implants with incorporated MNP. Comparison between simulation and experiments demonstrates the susceptibility to the design of MNP assemblies. Precise information about assembly geometry is crucial to improve the prediction accuracy.

Keywords: Agglomeration; Magnetic dipole-dipole interactions; Magnetic hyperthermia; Magnetic nanoparticles; Magnetic relaxations; Stochastic Langevin simulations.