Year

2009

Degree Name

Doctor of Philosophy

Department

Department of Chemistry - Faculty of Science

Abstract

This study explored the potential biomedical applications of polypyrrole (PPy). Electrical and topographic cues have been delivered to cells via composites of these conducting polymers, resulting in the successful control of cell behaviour. It was found that a clinically-relevant electrical stimulation protocol (250 Hz biphasic pulsed-current) delivered directly via PPy/poly(2-methoxy-5-aniline sulfonic acid) (PMAS) films can significantly promote PC12 nerve cell differentiation in the presence of nerve growth factor (NGF), and can initiate reversible neurite sprouting from PC12 cell in the absence of NGF. The ability to promote neural outgrowth on PPy/PMAS has important implications for improving the neural/electrode interface, and this may be used to effect in nerve regeneration. The same biphasic 250 Hz electrical stimulations were applied to a monolayer of endothelial cells on PPy/heparin films, and significantly enhanced endothelial cell migration was observed as a result. Combined with the ease of fabrication on metallic stents and the antithrombotic function of heparin, these materials may be utilized for modification of stents to improve the re-endothelialization process after implantation. Finally, aligned PPy/poly(styrene-β-isobutylene-β-styrene) (SIBS) nanofibrous scaffolds were fabricated by vapor phase depositing PPy onto electrospun SIBS fibrous mats. It was shown that this novel material provided a conductive and biocompatible platform for PC12 cell adhesion and differentiation. Neurite outgrowth was significantly influenced by the aligned fibers. High resolution AFM provided a closer inspection of the neurite outgrowths and revealed interesting physical interactions between the neurites and the aligned fibers. Aligned electroactive PPy/SIBS fibers have potential applications for improving the electrode-cellular interface of neural electrodes by encouraging guided neurite outgrowth toward the electrode through the use of electrical stimulation. The knowledge gained during the course of this study could form the basis for improving the cellular interface of neural electrodes and stents using conducting polymers.

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