Radiation Effects on Hybrid-Type Medical Materials

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During the course of the development of biomedical materials, sterilization is essential since a material is contaminated with bacteria. Therefore, the polymeric material must be capable of being sterilized without detriment. Sterilization techniques are categorized as physical or chemical ones. Physical methods include dry heat, steam, and ionizing radiation. Chemical sterilization methods by using ethylene oxide is also used widely. Unfortunately, conventional autoclaving method cannot be used for biomimetic materials because they contain heat-labile bioactive components such as proteins. Ethylene oxide gas fumigation causes a health problem by traces of toxic and carcinogenic gas remaining in the material after treatment. Ionizing radiations are able to kill bacteria without including neither heat nor substances affecting the quality of the materials and our health. Thus the irradiation sterilization, which has already been applied to the medical supplies, should be the final candid … More ate for sterilization of the hybrid-type biomedical materials containing proteins. To apply commercial irradiation sterilization technique to the protein-containing hybrid-type biomadical materials, it is necessary to examine radiation torelance of proteins as well as other components at a standard doze of 25kGy generally used for commercial-scale irradiation. There are very few data available for these purpse until now.In this project, to establish irradiation sterilization method for hybrid-type biomedical materials containing bioactive molecules together with artificial polymers, we examined radiation tolerance with 6OCo gamma-rays. We selected enzymes as a model of proteins. Furthermore, we designed various types of-biomedical polymers as well as hybrid-type materials for biomedical applications. Finally, it is concluded that the commercial irradiation sterilization method is applica ble to decontamination of enzymes under an appropriate condition such as dry or frozen state. Although radiation inactivation of enzymes in the aqueous solution was occurred, it could be depressed by control of the irradiation conditions. It is also concluded that the immobilized enzymesare much more stable than free ones for irradiation. These findings suggest that the irradiation sterilization will be useful for hybrid-type biomedical materials in future. Less