Effect of Subcellular Nanopillars with a High Aspect Ratio on the Cell-Electrode Coupling for Neuroelectronic Interfaces

Over the past twenty years, nanoscience has advanced rapidly, leading to significant developments not only in materials science and physics, but also impacting various fields from life sciences to engineering. Among these advances, micro- and nanoelectrodes ranging from micron to sub-micron in size, have been particularly important in neurosciences, where they are the primary functional elements of neuroelectronic devices designed for recording and electrical stimulation. Here we report on improvements in electrode fabrication and design, and the integration of nanoelectrodes with microelectrodes. In addition, as electrode dimensions decrease, new electrostatic and electrochemical effects emerge that enhance intracellular sensing applications. In particular, tight physical coupling between the electrode and the neuron leads to higher signal-to-noise ratio (SNR) of extracellular recordings due to better isolation of the electrode from noise, and recent applications of high aspect ratio nanostructures for neural applications show substantial passive improvement of extracellular recordings. Tight cell-electrode coupling relies on the reorganization of structural proteins within the cell, but the details of the mechanisms behind this reorganization are not fully understood, hindering the design of an ideal structure for high SNR passive recordings.<br/>In this study we push cell-electrode coupling in the nanoscale through the engineering of high-aspect ratio nanopillars with diameters below 100nm. These nanostructures allow us to uniquely probe neurons as they approach the diameter of curvature of sub-cellular features. These sub-cellular nanopillars are then integrated onto micro electrode arrays (MEAs) and in high-density large-scale arrays to investigate the neurons through a range of experiments. The fabrication of the nanopillars utilizes the nanometer resolution of electron beam lithography (EBL) combined with the conformality of atomic-layer deposition (ALD).<br/>To investigate the cell-chip coupling, E18 rat cortical neurons were cultured on the nanopillars on different platforms. The physical and structural characteristics were investigated through critical point drying (CPD), focused ion beam (FIB) milling of ultra-thin plasticization (UTP) preserved cells, and immunostaining. Whereas, the electrophysiological coupling was explored through nanopillar MEA recording with simultaneous patch clamp.