3D Printed Conducting Polymer Microelectrode Arrays for Electrical Stimulation of Neural Tissues – A-Proof-of-Concept

The context of the thesis is the field of three-dimensional (3D) conducting polymer (CP) electrodes and their application in bioelectronics. The thesis deals with the fabrication of 3D microelectrode arrays (MEAs) with CP pillars for 3D electrical stimulation (ES) of neural tissues. The cells were encapsulated within a polysaccharide-based biogel to form a 3D construct interfaced with the CP pillar arrays and differentiated in situ with ES. The ES was applied to maturing neural tissues derived from human induced pluripotent stem cells (hiPSCs) and human neural stem cells (hNSCs). The cells were exposed to CP poly(3,4-ethylenedioxythiophene)-polystyrenesulfonate (PEDOT:PSS) pillars that had been direct write printed in a gold array format. The aim of the thesis was to provide a proof-of-concept of the ability to use fabricated 3D microelectrode arrays for electrical stimulation of neural tissues. Hence, the thesis was aiming at validating the platform of 3D MEA chips with CP pillars on neuronal cultures and electrical stimulation and presenting the potential of the specific 3D MEAs with CP pillars for neurophysiological applications. This was achieved by fabricating 3D MEA chips with CP pillars and by using them in ES experiments differentiating clinically relevant cells which can be used for therapy related to neurological diseases and research. The MEA chips were shown to allow the recording of extracellular potentials when electrophysiological signals were acquired from neuronal cultures. The electrical stimulations of the cells provided with data revealing promising results related to the electrical activity of the cells. The experiments indicated that the pillars possess auspicious technical properties. However, based on the observations, handling of the MEA chips and electrical stimulation may damage the electrodes. According to the experiments, more studies are needed to determine an optimal surface treatment to ensure the attachment of the material with the cells on the surface of the MEA. Moreover, plasma treatment and Matrigel™ treatment need to be further assessed for secure and repeatable attachment results. Formation of 3D tissues using pillar arrays substantiates the platform for advanced clinically relevant neural tissue induction. The platform may be useful for both research and translation, including modelling tissue development, function and dysfunction, drug screening and regenerative medicine. In conclusion, this study provides a proof-of-concept of the use of 3D MEA with CP pillars in the context of ES of neural tissues