Development of new biocompatible magnetic materials and the application to hyperthermia of cancer

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We have investigated the magnetic materials which is used for hyperthermia of cancer under the high frequency alternating magnetic field (H) . The hysteresis loss heat generation and Curie temperature (Tc) have been measured for several materials. The biocompatibility of materials has been taken into consideration. The summary is listed as follows.1) Magnetic properties and the heat generation of Mg-Fe-M-0 (M=Ti, Si, K, Ca) oxides was investigated. In the Mg_<1+x>Fe_<2-2x>Ti_x0_4 system, the Curie temperature (Tc) decreased with increasing x, from 635K for x=0.0 to 200K for x=0.5. The heat generation Q=16W/g for x=0.0 at H=100 Oe decreased to 3W/g for x=0.35 at room temperature. We found that the Ti substitution is best for hyperthermia.2) Ultra fine particles of Fe_3O_4 were made by the chemical method. The particles with diameter less than 2Onm showed the lower Tc than bulk (850K) . Tc decreased with decreasing the diameter and 660K for 5nm was achieved as minimum Tc. It is concluded that the decrease of diameter is an appropriate method to decrease the Tc.3) Ultra fine particles of Co wera investigated. It was difficult to obtain the Co particles with a diameter less than 2Onm. Tc of the particles with 2Onm in diameter was almost same to bulk value. Co particles are not appropriate for hyperthermia.4) Artificial metallic superlattices including Fe atomic layers were made. The minimum of Tc for alpha-Fe was 350K at 1.3 monolayer (ML) and that for gamma-Fe was 300K at 0.8 ML of Fe. It was concluded that such superlattices with ultra thin atomic layers has the appropriate Tc but could not be used for hyperthermia, because the quantity of production by one process is very small.