Electrodeposited poly(3,4-ethylenedioxypyrrole) films as neural interfaces: Cytocompatibility and electrochemical studies

Abstract

Conducting polymers have been extensively reported as promising coating materials for applications involving interactions with electrically excitable tissues. Specifically, metal electrodes functionalized with conducting polymer coatings have been employed as biointerface presenting tailored properties to promote electrode integration as well as chronic functionality. Currently, polypyrrole (PPy) and poly(3,4-ethylenedioxythiophene) (PEDOT) represent the most extensively studied conducting polymers, exhibiting favourable electrochemical properties and biocompatibility. In this paper, we study electrodeposited poly(3,4-ethylenedioxypyrrole) (PEDOP), a conducting polymer which is structurally related to both PEDOT and PPy, and is expected to outperform its "parent" polymers in terms of electrochemical properties and biocompatibility. The performance of PEDOP doped with chloride/phosphate, p-toluenesulfonate or polystyrene sulfonate was subsequently investigated to assess the efficacy of these ionic dopants in promoting electrochemical stability and neural cytocompatibility. Electrodeposited PEDOP films exhibited a high charge storage capacity (50.07 ± 6.96 mC cm-2), charge injection capacity (203 ± 24 µC cm-2) and substantial stability (performance loss of 0.49 ± 0.06 % after 100 000 stimulation pulses). Furthermore, PEDOP films promoted enhanced neuron outgrowth and viability relative to control substrates. In particular, PEDOP/PTS was shown to increase the average neurite length three times when compared with cells cultured on bare Pt control. Consequently, due to its favourable electrochemical characteristics together with high neural cytocompatibility, PEDOP can be indicated as a promising alternative to PPy and PEDOT in the field of neural science.

Dopant-Dependent Electrical and Biological Functionality of PEDOT in Bioelectronics

“…In each case, a typical, gradual increase in current density was observed in consecutive CV scans and was associated with the growth of a conducting polymer layer [21]. As easily observed from the magnitude of achieved currents, the efficiency of the polymerization process was dependent on the choice of a dopant/solvent system [21]. Among all investigated systems, the most prominent increase in current intensity was noted for PEDOT/PF 6 .…”

“…Eventually, the anodic potentials of 1.8 V, 1.2 V, and 1.2 V were chosen for nBu 4 NPF 6 /ACN, LiClO 4 /H 2 O, and NaPSS/H 2 O, respectively, and the corresponding polymerization curves of EDOT were plotted in Figure 1G-I. In each case, a typical, gradual increase in current density was observed in consecutive CV scans and was associated with the growth of a conducting polymer layer [21]. As easily observed from the magnitude of achieved currents, the efficiency of the polymerization process was dependent on the choice of a dopant/solvent system [21].…”

“…Surface morphology directly affects cellular adhesion. Rough topologies of conducting polymers were found to provide more suitable interfaces for cell attachment, compared to smooth metallic surfaces, conventionally applied as neural interfaces [21,38]. Nevertheless, other studies reported that the roughness factor is not decisive itself, but a crucial role is played by a correlation of cell size with the size of topographical details [34,39].…”

Analysis of a poly(ε-decalactone)/silver nanowire composite as an electrically conducting neural interface biomaterial

“…Electrochemical studies were performed according to our previously established protocol [ 49 ] by means of a PARSTAT 2273 potentiostat in a three-electrode set-up, comprising Pt foil (0.1 mm thickness, 99.9% purity, produced by Mennica-Warsaw, Poland), EDL- and EDL:Ag-coated Pt/glass slide as a working electrode, Ag/AgCl as a reference electrode and glassy carbon rod as an auxiliary electrode. Cyclic voltammograms (CVs) were collected in 0.1 M KCl solution, within the potential range from − 0.8 to 1.0 V (vs. Ag/AgCl) at 100 mV s − 1 for 5 CV cycles.…”

“…Cytocompatibility of the pristine EDL and EDL:Ag composites was determined with primary cultures of a mixed neural population obtained from the ventral mesencephalon of E14 rat embryos [ 49 ]. The embryos were obtained by laparotomy from time-mated female Sprague-Dawley rats delivered by Charles River Laboratories.…”