Expanding the Neuroanalytical Toolkit: Electrochemical Measurements of Neurotransmitters Using Poly(3,4-Ethylenedioxythiophene) Conducting Polymer Materials

Abstract

The human brain is an extraordinarily complex organ. The process of neurotransmission gives rise to sensory experience, cognition, and decision-making. Many common diseases of the brain are incurable and their symptoms are poorly treated. To better understand the underlying molecular problems in disease states, sensitive, selective, and rapid measurements of biomolecules are needed. Given the complexity of making biological measurements in vitro or in vivo, inquiring scientists must choose measurement tools wisely. While traditional electrode materials have been used to great success, conducting polymers such as PEDOT are an excellent way to modify or improve existing measurement tools. The chemical, spatial, and temporal resolution of in vivo and in vitro measurements can be improved, all while increasing the longevity of the sensor. Compared to existing electrode materials, PEDOT is amenable to a larger variety of substrates, easier to process, inexpensive, and has excellent electrochemical behavior for the detection of neurotransmitters. We have demonstrated the utility of PEDOT by fabricating and characterizing the first device for the separation of biogenic amines, and the first device for high-throughput measurements of exocytosis from single PC12 cells. These devices will allow scientists to inexpensively and rapidly study the effects of pharmacological challenges to model systems in disease states. A PEDOT and Nafion composite polymer coating has been developed for microelectrodes, granting increased sensitivity and selectivity towards dopamine. These improvements resulted in the first in vivo electrochemical measurements of dopamine transients without administration of a reuptake inhibitor. Lastly, we have expanded the chemistry of polythiophenes by developing the synthesis of oligo-EDOT:Nafion nanoparticles. These nanoparticles are easily prepared, inexpensive, and enable quantiative spectroscopic interrogations of water content in organic solvents.