A key limitation associated with conducting polymers (CP) for implantable electrodeapplications is their inferior physico-mechanical properties and the effect of this onbiological performance. This research investigates the physico-mechanical cues ofconventional conducting polymer coatings and aims to understand their effects on neuraladhesion and neurite extension. The underlying hypothesis was that the biologicalperformance of CPs can be effectively controlled by physical cues such as surfacetopography and mechanical softness.Poly(3,4-ethylenedioxythiophene) (PEDOT) doped with perchlorate, benzenesulfonate,tosylate (pTS), dodecylbenzenesulfonate and polystyrenesulfonate were comparedacross a range of baseline material properties. Additionally, the deposition charge usedto produce PEDOT was varied from 0.05 to 1 C/cm2 to determine an optimal thickness forelectrode coatings. To address the need for electroactive biomaterials with improvedneural interfacing, nanobrush-CP hybrids were fabricated. Dense poly(2-hydroxyethylmethacrylate) (PHEMA) brushes were grafted via surface-initiated atom transfer radicalpolymerisation (SI-ATRP). PEDOT/pTS was electrochemically deposited through thisnanobrush substrate. The formation of the hybrid was confirmed and characterisedacross implant performance metrics.The physical, mechanical, electrical and biological performance of PEDOT coatings wasused to assess ideal fabrication parameters, optimised for neural cell interactions.Nanoindentation techniques were used to yield the first quantitative values for stiffnessmoduli of electrodeposited CP coatings on metal substrates. It was found that thenodularity of the CP surface increased with increasing coating thickness and decreasingdopant size. A major finding of this study was that high roughness of conventionallydoped PEDOT produced on the micron scale, prevented attachment of neural cells.Consequently, thin PEDOT films doped with the low toxicity anion, pTS, supported thegreatest cell attachment and neurite outgrowth. Electrochemical performance wasanalyzed and supported the finding that thin PEDOT/pTS provides significant biologicaland electrochemical advantages over platinum electrodes. The nanobrush/CP hybridfurther improved the electrochemical properties of conventional CPs and offers a newapproach for selective cell attachment via the CP coated region of the brush substrate.This thesis demonstrates that the biological performance of CPs is strongly influenced bythe physico-mechanical properties with optimal coatings produced in the sub-micronrange using conventional doping ions. A new hybrid nanobrush/CP is presented withfabrication parameters which can be tailored for target material properties. Future workwill focus on delineating the interfacial structure of the hybrid to optimise the cushioningeffect of the brushes for neural interface applications.
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