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

研究了高频交变磁场(H)作用下用于肿瘤热疗的磁性材料。测量了几种材料的磁滞损耗、放热和居里温度。材料的生物相容性已被考虑在内。1)研究了Mg-Fe-M-0(M=Ti，Si，K，Ca)氧化物的磁性和生热行为。在Mg_&lt；1+x&gt；Fe_&lt；2-2x&gt；TixO_4体系中，居里温度随x的增加而降低，从x=0.0时的635K下降到x=0.5时的200K。在室温下，当x=0.35时，当H=100Oe时，x=0.0时的产热Q=16W/g，降至3W/g。2)用化学方法制备超细Fe_3O_4。粒径小于20 nm的纳米粒子的玻璃化转变温度低于块体(850K)。T_c随直径的减小而降低，最小T_c为660K，最小T_c为5 nm。结果表明，减小直径是降低Co超细颗粒的一种合适的方法。很难得到直径小于20 nm的Co粒子。粒径为20 nm的颗粒的相变温度与体积值基本一致。4)制备了含Fe原子层的人造金属超晶格。在1.3单分子层(ML)下，α-Fe的最小T_c为350K，在0.8 M L时，γ-Fe的T_c为300K。结果表明，这种具有超薄原子层的超晶格具有合适的T_c，但由于一次生产的量很小，不能用于热疗。

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.