Electrochemical Deposition and Evaluation of Conductive Polymer Coating on Biodegradable Magnesium Implants for Neural A
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Electrochemical Deposition and Evaluation of Conductive Polymer Coating on Biodegradable Magnesium Implants for Neural Applications
Meriam A. Sebaa1*, Shan Dhillon1*, Huinan Liu1,2,# 1 Department of Bioengineering, University of California, Riverside, CA 92521 2 Materials Science and Engineering Program, University of California, Riverside, CA 92521 *Equally contributed; #corresponding to [email protected] ABSTRACT In an attempt to develop conductive, biodegradable, mechanically strong, and biocompatible nerve conduits, pure magnesium (Mg) was used as the biodegradable substrate material to provide strength while the conductive polymer, poly(3,4ethylenedioxythiophene) (PEDOT) was used as a conductive coating material to control Mg degradation and improve cytocompatibility of Mg substrates. This study explored a series of electrochemical deposition conditions to produce a uniform, consistent PEDOT coating on Mg substrates. The microstructure and morphology of the coating and Mg were visualized using scanning electron microscopy (SEM). The elemental composition of the surface was quantified using energy dispersive X-ray spectroscopy (EDS). Adhesion strength of the coating was measured using the tape test following the ASTM-D 3359 standard. The SEM results showed uniform and consistent PEDOT coating, and EDS analysis confirmed the elemental composition of PEDOT. The adhesion strength of PEDOT coating was within the classifications of 3B to 4B. INTRODUCTION Treating patients with peripheral nerve damage is challenging due to the limited ability of nerves to self-regenerate. Current treatments for damaged nerves include nerve guide conduits, which are used to guide the growth of injured nerves. It is crucial that the materials for nerve guide conduits are designed to be non-toxic and be able to guide cell growth and differentiation into expected cell types when implanted into the body. Magnesium (Mg) was chosen as the metallic support due to its excellent mechanical strength and electrical conductivity, both desirable properties for neural applications. Moreover, Mg is used clinically as a neuro-protective agent [1-4]. Mg infusion causes rises in cerebrospinal fluid and brain Mg concentrations. It has been shown to protect against further damage with acute stroke [3, 4] and cerebral ischemia [5], and to prevent atrial fibrillation post coronary bypass surgery [6, 7]. These findings make Mg an excellent candidate for implantation as a nerve guide conduit if the release of Mg ions can be properly controlled with coatings. Mg is known to degrade at a rapid rate, causing an unfavorable increase in pH [8, 9]. The conductive polymer poly (3,4-ethylenedioxythiophene) (PEDOT) was chosen as the coating material due to its conductivity (electrical conductivity ranges found from 20 to 132 S/cm) and
biocompatibility [10, 11]. It is also more electrochemically stable than its counterpart, polypyrrole [12]. The hypothesis is that PEDOT coatings on Mg will slow down the degradation rate of Mg in body fluids allowing for a more favo
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