Effects of Ionizing Radiation on Biopolymers for Applications as Biomaterials

Biopolymers, including extracellular matrix proteins and polysaccharides, are used as substrates for cell culture and scaffolds in tissue engineering. Ionizing radiation, for example with gamma rays or electron beams, is used to sterilize materials and to modify the physical and chemical properties of materials. The principles of the effect of ionizing radiation on biopolymers are discussed in this review article. Among the types of ionizing radiation, gamma rays and electron beams are widely used to sterilize biomaterials and construct medical devices. Water molecules are split by irradiation with ionizing radiation to give hydrated electrons, proton radicals and hydroxyl radicals. These reactive molecular species react with polymer chains to provoke scission or crosslinking reactions. Both the scission and crosslinking of the polymer chains can occur, depending on the types of polymer and irradiation conditions. Sterilization of materials is necessary if they are used in medical devices and implants. The advantages and disadvantages of ionizing radiation in comparison with other methods of sterilization are also discussed. Irradiations with strong gamma rays on the three types of biopolymers—Type I collagen, wool keratin and alginate—are described as examples of biopolymers. Ionizing radiation is a very useful tool for sterilizing materials and constructing medical devices, but it is important that we know its merits and demerits, as well as the limitations, safety and risks, of its applications.