Interfacing cultured neurons to planar substrate microelectrodes: characterization of the neuron-to-microelectrode junction☆

Abstract This paper focuses on the characterization of the bioelectrochemical interface that develops whenever neurons are cultured directly on top of planar arrays of noble metal microelectrodes. The characterization is based on the equivalent circuit analysis of a neuron membrane coupled to a metallic planar microelectrode. The membrane is described according to the Hodgkin-Huxley model, using a set of equations specialized for the description of action potentials generated by chick embryo dorsal root ganglia (DRG) neurons. An ad-hoc modified version of the circuit analysis program spice allows one to simulate the signal corresponding to an action potential as it should result from the microelectrode transduction. By varying the membrane-to-electrode coupling and other biophysical parameters, simulation signals of different durations, intensities and shapes are generated. The appropriateness of the model is verified by adapting simulation signals to experimental ones, obtained by preliminary experiments with DRG neurons cultured on a microelectrode array. The potentialities and limitations of the equivalent circuit approach as a tool for the characterization of a long-term (i.e. days) coupling of neurons to planar microelectrodes are discussed.