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

Abstract

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 subsecond 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. Neurotransmitters are molecules that allow neurons to send signals to target cells to communicate, influencing behaviors like reward and motivational habits.1-3 Dopamine (DA) is a neurotransmitter of the central nervous system with a key role in Parkinson desease. 4 Since dopamine is electro-active, it can be easily oxidized at an electrode surface with electrochemical methods, for example using Fast Scan Cyclic Voltammetry (FSCV). 5,6 Other molecules such as serotonin (5-HT), norepinephrine and adenosine are electro-active neurotransmitters that can be measured electrochemically. 6,7 The problem is that these molecules, except for adenosine that is oxidized at higher potentials, 8,9 have all very similar oxidation and reduction potentials and it is difficult to distinguish them in vivo. 1In fact, ascorbic acid (AA) and 3,4-dihydroxyphenylacetic acid (DOPAC) may completely mask dopamine detection in the brain. 10DOPAC is a metabolite of dopamine and ascorbic acid is an antioxidant, both present at high concentration in the brain and may interfere with dopamine.13 Therefore, it is very important to develop electrode materials with sufficient sensitivity and selectivity for in vivo detection of dopamine, serotonin and adenosine.Carbon has been shown to be one of the best material to perform such measurements in vivo. 3,11,12 Previous studies have been done to increase the sensitivity and selectivity of bare carbon fiber electrodes.15 Conductive polymers increase the surface area of the electrode and enhance the sensitivity. Among the various conductive polymers, poly(3,4-ethylenedioxythiophene) (...

Recent Advances in Electrochemical and Optical Sensing of Dopamine

“…Demuru et al (2017) developed the surface of CFMEs by using electro-polymerization of Nafion perfluorinated resin and 3,4-ethylenedioxythiophene (EDOT) with two surfactants such as sodium dodecyl sulfate (SDS) or sodium dodecyl benzene sulfonate (SDBS) to synthesize coatings [114]. The surfactants used increased the solution conductivity and decreased the surface tension at the electrolyte electrode interface.…”

Electrodeposited PEDOT:Nafion Composite for Neural Recording and Stimulation

“…There are a limited number of reports in the literature of PEDOT:Nafion composites to date . Wang and Olbricht reported a procedure to electrodeposit PEDOT:Nafion on Pt electrodes starting from a commercially available Nafion solution, providing both electrochemical and surface morphology characterization .…”

“…These examples show that PEDOT:Nafion is an attractive material for biomedical device applications. However, none of the previous PEDOT:Nafion composites were designed to record or stimulate neural activity in vivo …”

Nanomaterials-Based Electrochemical Sensors for In Vitro and In Vivo Analyses of Neurotransmitters

“…The positively charged cysteamine self-assembled monolayer (SAM) discriminated DA from the negatively charged interference molecules (e.g., AA) on the aptamer, which provided the selectivity to the fabricated sensors. In the DA detection, the potential interference of AA and UA may be avoided by the careful design of the electrode and the selection of materials [59]. However, interference from structurally related neurochemicals (e.g., DA and EP) is challenging to avoid.…”