Studies on development and characterization of functional conductive biomaterials by a radiation-based technique

Abstract

Radiation has been widely employed to modify material properties as radiation of ionized beam can form free-radicals and lead to various reactions such as surface modification, crosslinking, degradation, and sterilization. Radiation technology offers several benefits as radiation-related reactions are typically simple and easy to induce in various environments without chemical additives. In particular, in the field of biomaterials, radiation technology, which requires no toxic compounds, has been applied to engineer various biomaterials for their uses as tissue engineering scaffolds, drug delivery carriers, and biosensors. Especially, conductive biomaterials have to maintain conductivity and stability; however, such characteristics (simultaneous presenting good conductivity and stability) are typically hard to achieve in general. In my thesis, firstly, I exposed conducting polymer (e.g., polypyrrole (PPy)) based bioelectrodes to gamma-ray for sterilization and investigate their characteristics. Although gamma-ray sterilization has been commonly used in medical products due to simple and uniform sterilization, the effects of gamma-ray radiation on conductive polymers were poorly understood. The gamma-ray irradiated PPy bioelectrodes (γ-PPy) showed the increased oxygenation and hydrophilic surfaces, without alteration of their electrical impedance and conductivity. In addition, gamma-ray irradiation was effective for PPy sterilization as evidenced by complete eradication of gram positive and negative bacteria. In addition, gamma-ray irradiation was utilized to introduce zwitterionic properties of PPy electrode for their reduction of biofouling. Methacryloyloxyethyl phosphorylcholine (MPC) with different concentration (0.1 M and 0.2 M) was grafted on PPy electrodes by gamma-ray irradiation. PPy electrodes modified with 0.2 M MPC (PPy-g-MPC0.2) revealed excellent anti-biofouling properties compared to bare PPy electrodes, as proven by multiple tests, including serum protein adsorption, fibroblast adhesion, bacteria adhesion, and scar tissue formation in vivo. Importantly, electrical properties of PPy-g-MPC0.2 were similar to bare PPy electrodes. Gamma-ray induced zwitterionic polymer grafting on PPy electrodes by in situ polymerization with gamma-ray radiation will benefit the development of highly biocompatible and functional bioelectrodes. Altogether, in my thesis, I successfully demonstrated that radiation-based techniques can be useful for the biomedical applications of conductive polymer-based biomaterials.