Extracellular Recording from Neuronal Networks Cultured on Hydrogel-coated Microelectrode Array

Abstract

Microelectrode array (MEA) has been widely used for ensemble recording. One of the advantages of MEA recording is its capability of studying correlation between network structures and the ensemble activity-patterns. Simple neuronal networks, from which activities of individual cells can be identified, are promising for this purpose. We have developed a mask-free cell-patterning method named “micropipette drawing”. In this method, a thin hydrogel layer is formed on the surface of MEA substrates, which acts as the support for growth-guidance patterns. Here in this work, we tested whether electrical signals could be detected through this gel layer. Rat cortical neurons were cultured on substrates with guiding patterns. Electrical activities could be detected after 7 days in vitro (DIV) in both patterned and normal cell cultures, though the signal to noise ratio in the normal culture was clearly higher than that in the patterned culture. Frequency analysis demonstrated that the difference of the power spectra between these cultures was particularly significant in high frequency regions. Decreases in high-frequency components were more prominent in the signals obtained from the patterned cultures. This result suggested that the hydrogel layer acted as low-pass filters probably due to its capacitive properties. The next step is to establish a method to form hydrogel layers, which maintain growth-guidance properties and have better frequency characteristics.