Surface modification of bio-electrodes for the improvement of their biocompatibility and performance

Abstract

Bioelectrodes are widely used in a variety of biomedical applications, such as biosensors, pacemakers and neural prostheses. For such applications, performance and biocompatibility of the bioelectrodes are essential. As biological and electrochemical outcomes of the bioelectrodes are mostly determined by the surface interactions with their surroundings, in this thesis, bioelectrode surfaces were modified to make them more suitable for biomedical applications. Specifically, I developed techniques for electrochemical surface modification of bioelectrodes using conductive and natural biocompatible polymers to render electrodes exhibiting improved electrical/electrochemical performances and biocompatibility. First, preparation of polydopamine (PDA)/polypyrrole (PPY) film on an indium tin oxide (ITO) electrode via an electrochemical method was studied. PDA/PPY films were successfully synthesized exhibiting greatly increased adhesion strengths of up to 3.7 ± 0.8 MPa and 2-3 orders lower electrochemical impedances than a bare electrode. This electrochemical deposition of adhesive and conductive PDA/PPY offers a facile and versatile electrode modification for various applications. Second, material and biological properties of PDA/PPY film were studied. The electrical properties of PDA/PPY-coated electrodes were superior to PPY-coated electrodes. The proliferation and differentiation of C2C12 myoblasts and PC12 neuronal cells on PDA/PPY electrodes were enhanced. Electrical stimulation of PC12 cells on PDA/PPY electrodes further promoted neuritogenesis. In vivo electromyography (EMG) signal measurements demonstrated more sensitive signals from tibia muscles when PDA/PPY-coated electrodes was used, revealing PDA/PPY to be a potential high-performance biomaterial for various biomedical applications. Finally, the electrochemical coating of dopamine-conjugated hyaluronic acid (DA–HA) conjugates for effective antifouling was studied. The impedance of the DA–HA-modified electrodes remained similar to those of bare electrodes. The DA–HA-modified electrodes showed decreased non-specific protein adsorption and minimal adhesion of fibroblasts. The electrodeposition of DA–HA can also be potentially applied for general anti-fouling surface modification for various applications. In conclusion, this thesis demonstrates that diverse surface modifications of bioelectrodes for enhanced electrical/electrochemical properties as well as improved biocompatibility for various biomedical applications.