Quantity Determination of Magnetic Particles Intravenously Administered to Mice Tissues Using Magnetization Measurements

This paper presents a method that has been developed to determine the quantity of accumulated magnetic particles in mice tissues using magnetization measurements. Dispersions of platelet Fe₃O₄ particles with the size of 30-50 nm and a saturation magnetization of ~80$ Am²/kg were intravenously administered to mice. Primary tissues were dried to measure the magnetization. The amounts of Fe₃O₄ particles accumulated in the tissues were obtained by dividing the magnetization of tissues by the magnetization of Fe₃O₄ particles under a magnetic field of 39.8 kA/m. A remarkable accumulation of particles was observed in the liver and the spleen, being supported by the observation of tissues using Prussian blue staining. Total Fe₃O₄ particles accumulated in primary tissues were ~38 -40 and 40-44 wt% against the particles in administered dispersions with 3 and 0.4 wt% contents, respectively. The method developed in this paper is considered to be effective for verifying magnetic hyperthermia and thermoablation therapies, in which the quantity of accumulated particles directly reflects the heating power required for those therapies.