A Bespoke Neural Chip Platform & Novel Microelectrode Design for the Recording of Human hNT Neurons

Abstract

Microelectrode array (MEA) based systems are becoming increasingly useful tools for recording the electrical activity of neuronal networks cultured in vitro. However, few studies have focused on the electrical characterisation of neurons that are derived from the NTera2 stem cell line (referred to as NT2 or hNT) cells. The motivation of this research is to design and develop an MEA based neural chip platform and use the developed platform for the neural recording of human hNT neurons. The thesis presented makes three main scientific contributions. The first scientific contribution is the development and validation of the neural chip platform. We developed a bespoke 32-channel MEA based neural chip platform that has a comparable noise level (input-referred noise < 2 µV) with commercial systems. The system is compact and inexpensive at the cost of $2753, which is more than 10-20 times less than the price of commercial systems. The software is user-friendly and straightforward for customisation. The second scientific contribution is the design and development of a new MEA with novel electrode designs. First, we designed and developed two generations of MEAs with gold and platinum (Pt) electrodes that are low-cost and simple to fabricate. Secondly, we deposited the conducting polymer poly (3,4- ethylenedioxythiophene) (PEDOT) onto the electrodes of the 2nd generation MEAs using electrochemical deposition to exploit its low impedance properties. Thirdly, we deposited Pt nanograss (Ptng) using a novel and effective galvanostatic electrochemical deposition (GSED) method. We determined that the PEDOT and Ptng coating significantly improved the electrochemical properties and significantly reduced the impedance of Pt electrodes. In addition, we found that the proposed GSED method could provide a relatively uniform electrode surface in comparison to the conventionally used potentiostatic electrochemical deposition method. The final contribution of the thesis is the first time extracellular recording of hNT neurons using the developed neural chip platform with gold, PEDOT and Ptng electrodes. Firstly, we validated the platform with the spontaneous neural recording of hNT neurons using the 1st generation MEA. Secondly, we performed neural recording using PEDOT and Ptng coated 2nd generation MEAs and found that our platform provided a better signal-to-noise ratio compared with the commercial system. Finally, we demonstrate how neural bursting from hNT neurons could be observed for the first time using PEDOT and Ptng electrodes. In addition, we quantify exhaustively the bursting that occurs and report this for the first time. Observing the phenomenon of bursting in hNT neurons, for the first time, on our developed platform is scientifically significant to the hNT community as it serves to rebalance the perspective about the electrical characteristics of hNT neurons to be equivalent to those observed in primary neurons which now matches the primary behaviour observed chemically from this important cell type.