Capacitive Composites Made of Conducting Polymer and Lysozyme: Toward the Biocondenser

Conducting polymer/protein composites, P(EDOT-LZ), of poly(3,4-ethylenedioxythiophene) (PEDOT) and lysozyme, a protein with bactericidal activity, have been prepared by in situ anodic polymerization. The stability of the composite obtained from a polymerization medium consisting of an acetonitrile:water solution (1:4 v/v) with a 1:1 monomer:lysozyme mass ratio is better than that of the individual conducting polymer, while the electrical conductivity and capacitive behavior of the two systems are very similar. Incorporation of the enzyme produces drastic changes in the morphology of PEDOT, resulting in the formation of very homogeneous aggregates with cotton flake morphology that has been shown to be hollow. Multilayered systems formed by alternating layers of PEDOT and P(EDOT-LZ) have been examined, even though results indicated that they do not show any practical advantage with respect to the individual P(EDOT-LZ) films. Adhesion assay using four eukaryotic cellular lines have evidenced that the behavior of P(EDOT-LZ) as a supportive matrix is still better than that of PEDOT. The bactericidal activity and the favorable response toward eukaryotic cells combined with its electrochemical properties suggest that P(EDOT-LZ) is a potential candidate for the fabrication of bioelectrochemical capacitors for in vivo implants. In order to examine this possibility, the electrochemical and capacitive properties of P(EDOT-LZ) coated with eukaryotic cellular monolayers have been investigated. Electrochemical impedance spectra reflect important differences in the response of P(EDOT-LZ) and PEDOT surfaces, which are independent of the cell line, when these materials act as supportive cellular matrices.