Heme protein-mediated synthesis of PEDOT:PSS: enhancing conductivity by inhibiting heme degradation

Abstract

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is a conducting polymer used in regenerative medicine, solar energy conversion, OLEDs, and biological sensing. PEDOT:PSS can be synthesized with a wide range of biomolecular oxidants including hemoglobin, catalase, horseradish peroxidase, soybean peroxidase, and laccase. Unfortunately heme proteins have been found to degrade during polymer synthesis, limiting their utility. We show that the peroxidase substrate, 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS), inhibits heme degradation during hemoglobin-mediated synthesis of PEDOT:PSS, measured by fluorescence emission. Four-point probe measurements show that films of PEDOT:PSS are more conductive when synthesized in the presence of ABTS. Characterization of the resulting PEDOT:PSS films using visible and near IR spectroscopy shows that ABTS produces a bipolaron rich polymer, as expected if heme degradation is inhibited. Conductivity is further enhanced (31 S cm⁻¹) when an iron chelator, EDTA, is used in combination with ABTS.