Electrochemical deposition and evaluation of electrically conductive polymer coating on biodegradable magnesium implants
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Electrochemical deposition and evaluation of electrically conductive polymer coating on biodegradable magnesium implants for neural applications Meriam A. Sebaa • Shan Dhillon • Huinan Liu
Received: 31 May 2012 / Accepted: 15 October 2012 / Published online: 27 October 2012 Ó Springer Science+Business Media New York 2012
Abstract In an attempt to develop biodegradable, mechanically strong, biocompatible, and conductive nerve guidance conduits, pure magnesium (Mg) was used as the biodegradable substrate material to provide strength while the conductive polymer, poly(3,4-ethylenedioxythiophene) (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 large three-dimensional Mg samples. A concentration of 1 M 3,4-ethylenedioxythiophene in ionic liquid was sufficient for coating Mg samples with a size of 5 9 5 9 0.25 mm. Both cyclic voltammetry (CV) and chronoamperometry coating methods produced adequate coverage and uniform PEDOT coating. Low-cost stainless steel and copper electrodes can be used to deposit PEDOT coatings as effectively as platinum and silver/ silver chloride electrodes. Five cycles of CV with the potential ranging from -0.5 to 2.0 V for 200 s per cycle were used to produce consistent coatings for further evaluation. Scanning electron micrographs showed the microporous structure of PEDOT coatings. Energy dispersive X-ray spectroscopy showed the peaks of sulfur, carbon, and oxygen, indicating sufficient PEDOT coating. Adhesion strength of the coating was measured using the tape test
Meriam A. Sebaa and Shan Dhillon contributed equally to this study. M. A. Sebaa S. Dhillon H. Liu (&) Department of Bioengineering, University of California, Riverside, 900 University Avenue, Riverside, CA 92521, USA e-mail: [email protected] H. Liu Materials Science and Engineering Program, University of California, Riverside, Riverside, CA 92521, USA
following the ASTM-D 3359 standard. The adhesion strength of PEDOT coating was within the classifications of 3B to 4B. Tafel tests of the PEDOT coated Mg showed a corrosion current (ICORR) of 6.14 9 10-5 A as compared with ICORR of 9.08 9 10-4 A for non-coated Mg. The calculated corrosion rate for the PEDOT coated Mg was 2.64 mm/year, much slower than 38.98 mm/year for the non-coated Mg.
1 Introduction Injury to the peripheral nervous system (PNS) is a significant cause of morbidity and disability today. Although direct suture repair may be effective for short (\5 mm) nerve gaps, Nerve Guidance Conduits (NGC) are necessary to mechanically support and direct axonal sprouting between the injured nerve stumps when nerve defects or gaps are larger [1]. The biomaterial used for NGC must be biocompatible, should provide a guidance cue that can enhance nerve regeneration, and must be biodegradable while maintaining a mechanically stable architecture during the regeneration process. Current N
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