Surface PEDOT:Nafion Coatings for Enhanced Dopamine, Serotonin and Adenosine Sensing

Electro-polymerization of Nafion perfluorinated resin and 3,4-ethylenedioxythiophene (EDOT) with two different surfactants yielded nanoscale improved surface coatings on carbon fiber microelectrodes. Increased sensitivity and good selectivity for sensing sub-second release of dopamine, serotonin and adenosine in the presence of large concentrations of ascorbic acid and DOPAC was demonstrated. Two different surfactants were used during electro-polymerization: sodium dodecyl sulfate or sodium dodecyl benzene sulfonate. With the improved nanoscale coatings, the dopamine signal is increased by 4X-9X, while the serotonin signal is increased by 4X, and the adenosine signal is increased by 3X compared to bare carbon. We measured the highest sensitivity of ∼ 34 nA/μM (5X increase from the bare carbon fiber) with the EDOT:Nafion and sodium dodecyl benzene sulfonate. Dopamine selectivity can be achieved using the full voltammetry curves with respect to ascorbic acid, serotonin and adenosine using distinguishing features of the voltammograms, such as differences in reduction or oxidation potentials and with respect to DOPAC using lower signals. Serotonin can be distinguished from dopamine by the difference in reduction potentials. Furthermore, a shift toward less positive potentials for the adenosine oxidation was observed with the coated carbon fibers. The novel surface coated electrodes can potentially improve in vivo measurements.