title: Effects of dopants on the biomechanical properties of conducting polymer films on platinum electrodes.
abstract: Conducting polymers have often been described in literature as a coating for metal electrodes which will dampen the mechanical mismatch with neural tissue, encouraging intimate cell interactions. However, there is very limited quantitative analysis of conducting polymer mechanics and the relation to tissue interactions. This article systematically analyses the impact of coating platinum (Pt) electrodes with the conducting polymer poly(ethylene dioxythiophene) (PEDOT) doped with a series of common anions which have been explored for neural interfacing applications. Nanoindentation was used to determine the coating modulus and it was found that the polymer stiffness increased as the size of the dopant ion was increased, with PEDOT doped with polystyrene sulfonate (PSS) having the highest modulus at 3.2 GPa. This was more than double that of the ClO4 doped PEDOT at 1.3 GPa. Similarly, the electrical properties of these materials were shown to have a size dependent behavior with the smaller anions producing PEDOT films with the highest charge transfer capacity and lowest impedance. Coating stiffness was found to have a negligible effect on in vitro neural cell survival and differentiation, but rather polymer surface morphology, dopant toxicity and mobility is found to have the greatest impact.
authors.affiliation: Graduate School of Biomedical Engineering, University of New South Wales, Sydney, 2052, Australia.
authors.forename: Sungchul
authors.initials: S
authors.lastname: Baek
authors.forename: Rylie A
authors.initials: RA
authors.lastname: Green
authors.forename: Laura A
authors.initials: LA
authors.lastname: Poole-Warren
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena / Q000187:drug effects; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000737:chemistry*; D002448:Cell Adhesion / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D055119:Elastic Modulus / Q000187:drug effects; D004553:Electric Conductivity; D055664:Electrochemical Techniques; D004566:Electrodes; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects; D018020:Lithium Compounds / Q000737:chemistry / Q000494:pharmacology* / Q000633:toxicity; D051379:Mice; D008855:Microscopy, Electron, Scanning; D008970:Molecular Weight; D009474:Neurons / Q000166:cytology / Q000187:drug effects; D016716:PC12 Cells; D010472:Perchlorates / Q000737:chemistry / Q000494:pharmacology* / Q000633:toxicity; D010984:Platinum / Q000494:pharmacology*; D011108:Polymers / Q000737:chemistry*; D051381:Rats; D013451:Sulfonic Acids / Q000737:chemistry / Q000494:pharmacology* / Q000633:toxicity; D013499:Surface Properties
chemical_list: D019086:Bridged Bicyclo Compounds, Heterocyclic; D018020:Lithium Compounds; D010472:Perchlorates; D011108:Polymers; D013451:Sulfonic Acids; C121383:poly(3,4-ethylene dioxythiophene); D010984:Platinum; C054684:lithium perchlorate
keywords: biocompatibility; conducting polymer; dopant; nanoindentation; physico-mechanical properties