title: Electrochemical deposition and evaluation of electrically conductive polymer coating on biodegradable magnesium implants for neural applications.
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 × 5 × 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 micro-porous 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 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 (I(CORR)) of 6.14 × 10(-5) A as compared with I(CORR) of 9.08 × 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.
authors.affiliation: Department of Bioengineering, University of California, Riverside, 900 University Avenue, Riverside, CA 92521, USA.
authors.forename: Meriam A
authors.initials: MA
authors.lastname: Sebaa
authors.forename: Shan
authors.initials: S
authors.lastname: Dhillon
authors.forename: Huinan
authors.initials: H
authors.lastname: Liu
mesh_terms: D020341:Absorbable Implants; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000737:chemistry; D020099:Coated Materials, Biocompatible / Q000138:chemical synthesis* / Q000737:chemistry* / Q000494:pharmacology; D003343:Corrosion; D004553:Electric Conductivity; D055664:Electrochemical Techniques; D004595:Electroplating / Q000379:methods; D048091:Guided Tissue Regeneration / Q000295:instrumentation / Q000379:methods; D008274:Magnesium / Q000737:chemistry* / Q000494:pharmacology; D008422:Materials Testing; D008954:Models, Biological; D009431:Neural Conduction / Q000187:drug effects / Q000502:physiology; D011108:Polymers / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology; D013499:Surface Properties / Q000187:drug effects
chemical_list: D019086:Bridged Bicyclo Compounds, Heterocyclic; D020099:Coated Materials, Biocompatible; D011108:Polymers; C121383:poly(3,4-ethylene dioxythiophene); D008274:Magnesium