Thin film microelectrodes for electrochemical detection of neurotransmitters

An important signaling process in the nervous system is the release of chemical messengers called neurotransmitters from neurons. In this thesis alternative thin film electrode materials for applications targeting electrochemical detection of neurotransmitters in chip devices were evaluated. Microelectrodes made of the conductive polymer Pedot:tosylate were characterized with respect to their physical and electrochemical properties and transmitter release from large groups of neuronal PC 12 cells was measured at Pedot:tosylate microelectrodes. Carbon microelectrodes made of pyrolyzed photoresist and conductive polymer microelectrodes made of Pedot:Pss were also fabricated and used successfully to measure transmitter release from cells. The use of different thin film electrodes for low-noise amperometric measurements of single events of transmitter release from neuronal cells was studied. For this application a very low current noise is needed together with a large temporal resolution. It was shown, that resistive and capacitive properties of thin film electrode materials are determining their usefulness in low-noise amperometric measurements. An analytical expression for the noise was derived and experimental noise measurements supported the theory. As an alternative to low noise amperometry at single cells, a chip device was developed to measure transmitter release from large groups of neuronal PC 12 cells. The chip was used to study refueling of transmitter reservoirs and the concentrations of potassium needed in a physiological buffer to trigger transmitter release from PC 12 cells. The potential of the chip for electrochemical drug screening of neuroactive drugs was demonstrated.