Application of polypyrrole(PPy) as the media material for the release and the detection of a neurotransmitter

This paper presents the application of polypyrrole(PPy) as a medium material for the release and the detection of a neurotransmitter, i.e. epinephrine, using its electrically stimulated ion exchange property. Neuron signals are transmitted in a synapse, which is composed of releasing and detecting parts of neurotransmitters. PPy was electrochemically polymerized with NaDBS as dopants on Au electrode and then was incorporated with epinephrine by cation exchange process. The incorporated epinephrine was released by applying a controlled voltage and the released amount of epinephrine was determined using an ultraviolet(UV) spectrometry. Experimental results of the releasing part show that the released amount of epinephrine dependeds not only on the thickness and the size of PPy film but also on the releasing time. Spontaneously diffused epinephrine amount was measured to be only 18% of the voltage driven release amount. The absorbance change of epinephrine due to the applied potential during releasing process is negligible compared with that of the released epinephrine. Overoxidized PPy(OxPPy) for the detecting part shows a good cation permselectivity for the detection of epinephrine and the current is also higher than that at the Au electrode in the same concentration of the epinephrine. The current level is different with dopants with which the OxPPy film is polymerized and the sensitivity of the OxPPy electrode depends on the thickness of PPy film.