Magnetic Nanoparticle Relaxation in Biomedical Application

Abstract

Magnetic nanoparticles (MNP) are widely used in nanomedicine for diagnostic and therapeutic applications due to their unique magnetic relaxation properties. A prominent application is magnetic fluid hyperthermia (MFH), which describes use of therapeutic heat generated by magnetic excitation and relaxation processes of MNP in an alternating magnetic field (AMF) enabling tumor-confined cancer therapy. The heating efficiency of MNP depends on their size and magnetic properties as well as on the parameters of the AMF. The high degree of interdependency between these parameters makes the description of MFH very complex. The two established MNP heating theories, linear response theory (LRT) and Stoner–Wohlfarth model based theory (SWMBT), lack a comprehensive implementation of MNP dynamic relaxation processes. Advanced nonequilibrium magnetic relaxation simulations, however, provide an understanding of the fundamentals of their magnetic relaxation processes in AMF. They offer an appropriate model system for studying the interdependence of the above-mentioned parameters and are, therefore, a powerful tool predicting MNP heating behavior. Here, the implementation of MNP relaxation physics into Monte Carlo (MC-) simulations is shown in detail and the heating efficiency is determined in dependency of MNP magnetic size and anisotropy energy constant, as well as the AFM parameters. The results are compared to those determined from LRT and SWMBT and it is concluded that MC-simulations can be generally applied to predict MNP heating with superior results: Specifically, MNP particle heating increases with increasing the AFM, and a specific particle size can be predicted that maximizes the heating efficiency, while the dependency on magnetic anisotropy remains a topic of ongoing discussion. On a wider scope, the benefit and experimental applicability of MC-simulations in the biosensing and magnetic particle imaging research are briefly discussed, demonstrating the versatility of magnetic relaxation simulations.

Authors 3

1. U. Engelmann Aachen Applied Medical Engineering Medical Faculty Department of Medical Engineering and Applied Mathematics

   RWTH Aachen University · FH Aachen

   Affiliation as printed

   Applied Medical Engineering, Helmholtz Institute, Medical Faculty, RWTH Aachen University, Aachen, Germany

   Department of Medical Engineering and Applied Mathematics, FH Aachen University of Applied Sciences, Aachen, Germany

2. Carolyn Shasha

   University of Washington

   Affiliation as printed

   Department of Physics, University of Washington, Seattle, WA, USA

3. Ioana Slabu Aachen Applied Medical Engineering Medical Faculty

   RWTH Aachen University

   Affiliation as printed

   Applied Medical Engineering, Helmholtz Institute, Medical Faculty, RWTH Aachen University, Aachen, Germany