Quantitation method of loss powers using commercial magnetic nanoparticles based on superparamagnetic behavior influenced by anisotropy for hyperthermia

Local hyperthermia using magnetic nanoparticles has attracted attention as a less invasive cancer therapy. Accurate estimation of heat dissipation of magnetic nanoparticles is important for hyperthermia treatment. In this study, the magnetization properties and heat dissipation of Feraheme (R), Resovist (R), and Synomag (R)-D commercial magnetic nanoparticles was measured. The effective core diameter and anisotropy constant were estimated by the Langevin function taking into consideration the effect of anisotropy. The required frequency and intensity of an applied magnetic field with respect to the weight and concentration of magnetic nanoparticles in an assumed spherical tumor were estimated based on measurement and theory of magnetic relaxation. A method to quantitate realistic heat dissipation of magnetic nanoparticles in tumor tissue by measurement of their magnetization properties is introduced. Because the physical rotation of magnetic nanoparticles is inhibited in tumor tissue, the realistic heat dissipation is estimated by solidifying a mass of nanoparticles in an experimental sample. The specific loss power and intrinsic loss power as the heat dissipations of magnetic nanoparticles were estimated from the area of the magnetization curves. The results indicated that only the linear component of magnetization was associated with the loss powers. Our method to quantitate loss powers and the index for applied magnetic field will facilitate the clinical application of hyperthermia treatment using magnetic nanoparticles.