Magnetite Needle as Heating Mediator for Intracellular Hyperthermia of Tumor.

This is the authors' abstract. We don't add key points for this paper.

Magnetite needle, in which magnetite particles are molded into needle-shape, was developed and we applied it as a heating mediator for intracellular hyperthermia. We investigated the hyperthermic effect on solid subcutaneous gliomas in the femoral region of female F344 rats. Magnetite needles were inserted into the solid tumors, which were then irradiated by an alternating magnetic field (118 kHz, 384 Oe). The rats were divided into a control group that was not irradiated (control group), or a group that was irradiated for 30 min three times (treatment group), then we evaluated the hyperthermic effect on tumor growth. Tumors completely regressed in 75% of the treated rats. Histological observations showed that magnetite particles in the control group were localized only around the point of the tumor where the needle was inserted. However, the particles in the treatment group were widespread, and necrotic cells were observed throughout almost the entire tumor tissue. The magnetite particles were flowed away by blood flow as the tumor regressed, and so the needles did not require removal from the femoral region. Moreover, the administration of two magnetite needles required only three minutes, although the magnetite cationic liposomes were injected over at least 120min to prevent backflow. These results suggest that magnetite needles are simple and effective therapeutic particulate heating mediators that can be clinically applied to treat tumors.