MWCNTs/PEDOT:PSS nanocomposites-modified microelectrode array for spatial dynamics recording of epileptic discharges in multi-subregion of hippocampal slice

Abstract

The acute hippocampal slice is useful for understanding how epilepsy spatially initiates, propagates, and terminates in the hippocampus, which is vital to study the epileptic mechanism in it. However, it is challenging to detect the electrical signals of the main cell layer (the granular cell layer in the dentate gyrus (DG) and the pyramidal cell layer in CA1 and CA3a–c), which play an important role in epilepsy, because it is difficult to be accurately located by electrodes and typically show low throughput. In this study, a special in vitro microelectrode array (MEA) for rat hippocampal slices was fabricated. The recording sites of the MEA were designed along the main cell layer to record accurately the electrical signals of this layer in each hippocampal sub-region. A special “less-hydrophilic-MWCNTs/PEDOT:PSS modification method” for in vitro MEA was applied to deposit electrochemically the MWCNTs/PEDOT:PSS nanocomposites onto the surface of the microelectrodes, which significantly improved their performance with low impedance (36.41 ± 3.07 kΩ), small phase delay (−41.2 ± 4.90°), high signal-to-noise ratio (S/N = 5.4) and good biocompatibility. The application of high-K+-ACSF and D-AP5 (NMDA receptor antagonist) showed a neural signal projection pathway of the epileptic discharges in the hippocampal slice. The epileptic discharges originated in CA3b, where the neurons acted as a pacemaker, and spread to CA1 and DG bi-directionally along the main cell layer. Moreover, the epileptic discharges spread backward (CA3b to DG) faster than forward (CA3b to CA1). The MEA provides a reliable and sensitive dedicated biosensor for hippocampal slices.