Improving Cytocompatibility of Commercial PEDOT:PSS for Bioelectronic Applications

Conducting polymers have emerged as a strong candidate material for bioelectronic applications owing to their mixed ionic-electronic conduction which allows them to efficiently transfer charge in aqueous environments. Commercial formulations of water-dispersible poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) have facilitated development of flexible conductors, sensors, organic electronics and electrode interfaces. While PSS is an efficient counterion and dopant for PEDOT , its presence in excess to enable water-based processing can result in variable processability and electrochemical performance. While chemical crosslinking approaches can be used to address the stability of PEDOT:PSS in aqueous environments, it can hinder further processing. Importantly for bioelectronic applications, the release of excess PSS in aqueous environments from commercially based PEDOT:PSS materials can result in cytotoxicity. To ameliorate these effects, the use of physical separation was explored to remove the excess dopant. PEDOT:PSS dispersions were produced in N,N’-dimethylacetamide and separated by centrifugation. Analysis of the supernatant by NMR indicated the presence of PSS and the remaining polymer was blended with a polyurethane to produce a conductive elastomer. The electrochemical performance of the conductive elastomer and its resultant cytotoxicity profile were assessed as a function of PSS removal. Reducing the amount of PSS prior to preparation of the final conductive elastomer material was demonstrated to markedly improve the cytocompatibility of the material while retaining a degree of electrochemical functionality. These findings represent a key step in facilitating the translation of PEDOT:PSS-based materials to clinical applications.