Time Course Change of the Heat-generating Capability of Dextran Magnetite Complex (DM) in vivo

Dextran magnetite complex (DM) is a magnetic fluid that generates a large amount of heat in an AC magnetic field and that has been proposed for use in intracellular and intraarterial hyperthermia. In this study, an experiment was carried out to elucidate change in the heat-generating capacity of DM in vivo. Five hundred mg-Fe/kg of DM was intravenously administered to each of 45 C3H/He mice. The animals were sacrificed on 0, 1, 2, 4, 7, 14, 21, 28, and 56 days after the administration of DM. The liver and spleen of the animals were extirpated and exposed to an external AC magnetic field for 5 min. The rise in temperature and the concentration of iron in the specimens were measured and the net heat-generating capacity of the DM was calculated. For both the liver and the spleen, the rise in temperature was highest immediately after injection. It then decreased rapidly until, on the 28th day, no substantial heat generation was observed. On the other hand, the iron concentration remained elevated as late as the 56th day. Consequently, the net heat-generating capacity of the DM decreased rapidly and this was considered the result of the biodegradation of DM in the reticuloendothelial system. These results indicated that the time interval between administration of DM and exposure to external magnetic field is an important factor in the hyperthermia using DM.