Migration behavior of magnetic nanoparticles with chain-like structure under gradient magnetic field and its influence on magnetic hyperthermia

Magnetic hyperthermia uses magnetic nanoparticles (MNPs) to generate the heat used for damaging cancer cells under an alternating magnetic field. In fact, the MNPs tend to gather at the injection center and also occur the clustering phenomenon at the same time when injecting into tumor tissue, which however can ultimately result in the excessive concentration of heat in the injection site. Thus, this study aims at improving the MNPs concentration distribution after the injection behavior by considering the action of a static gradient magnetic field, and finally optimizes both temperature situation and thermal damage degree for tumor tissue during magnetic hyperthermia. The MNPs distribution inside a proposed liver tumor is simulated by adopting a Monte Carlo method with adaptive step size, which consists of enough number of small size particles used to analyze the behavior of migration, diffusion, and chain-like phenomenon. The research results demonstrate that the introduction of static gradient magnetic field can disperse the MNPs and form a chain-like distribution inside tumor, and can then expand the distribution range of MNPs, thereby optimizing the thermal damage degree of tumor tissue. In addition, a PID controller with proper setting coefficients is also proven to be able to improve the therapeutic effect for hyperthermia by shortening the rising time to the critical temperature when proper coefficients are set properly during therapy.