Heat dissipation characteristics of magnetite nanoparticles and their application to macrophage cells

We report the results of the study undertaken to determine relative contributions of Néel and Brownian relaxations on magnetic heat dissipation by investigating the physical, magnetic and heating characteristics of magnetite suspension dispersing particles ranging in average diameter from 10.0 to 15.7 nm. Heating characteristics depended on the primary particle size and the viscosity of the medium. In the case of the sample with average diameter of 12.5 nm, the effective specific absorption rate dropped by 27% (22.9×10−9 to 16.8×10−9 Wg−1Oe−2Hz−1). In contrast, the decrease of 67% (29.5×10−9 to 9.7×10−9 Wg−1Oe−2Hz−1) was observed for the sample with average diameter of 15.7 nm. The potential of these particles as thermal seeds was tested by feeding the macrophage and exposing them to an alternative current magnetic field strength and frequency of 40 Oe and 600 kHz, respectively. The uptake of magnetite particles by the macrophage was adequate to raise the temperature of cell suspension b y 8 °C required for thermal necrosis.