Carbon nanotube-based multi electrode arrays for neuronal interfacing: progress and prospects

Abstract

Carbon nanotube (CNT) coatings have been demonstrated over the past several years as a promising material for neuronal interfacing applications. In particular, in the realm of neuronal implants, CNTs have major advantages owing to their unique mechanical and electrical properties. Here we review recent investigations utilizing CNTs in neuro-interfacing applications. Cell adhesion, neuronal engineering and multi electrode recordings with CNTs are described. We also highlight prospective advances in this field, in particular, progress toward flexible, bio-compatible CNT-based technology.

Keywords: carbon nanotubes; multi electrode array; neuronal recording; stimulation.

Figure 1

A false-colored SEM image of fixed locust frontal ganglion neuronal cells cultured on carbon nanotube islands. The carbon nanotube islands were grown using the chemical vapor deposition method directly on a quartz support. For further details see Sorkin et al. (2009). Width of field of view is 77 μm.

Figure 2

Rat neuronal cultures on CNT islands. (A) Fluorescent confocal image of fixed neurons (red) and glia cells (green) cultured on a carbon nanotube island. Disk diameter is 20 μm. (B,C) HRSEM images of a neuronal process forming a loop around several CNTs (designated by arrows). The image in (C) corresponds to the area marked by the dashed box in (B). Clearly identifiable process segments were manually highlighted. Processes appear to bind to the carbon nanotube surface in a manner akin to that of tendrils. Adopted from Sorkin et al. (2009).

Figure 3

A neuro-glia cortical culture from embryonic rats grown on a carbon nanotube micro electrode array. Clusters of cells self-organized during culture development to position themselves on the electrodes. The distance between electrodes is 200 μm. Image acquired using a 3D confocal microscope (Shein et al., 2009).

Figure 4

Electrode-electrolyte interface and charge injection. (A) Schematic representation of capacitive (left) and Faradaic (right) charge injection mechanisms. While capacitive charge injection includes redistribution of charge in the electrode-electrolyte interface, Faradaic process includes transfer of electrons. (B) An electrical circuit model for mechanisms of charge transfer at the electrode-electrolyte interface. (C) A circuit model for extracellular recording and stimulation from neuronal tissue using a MEA linked to external amplifiers. The model demonstrates the electrochemical interface resistance and capacitance of the CNT electrode and the solution derived shunt capacitance as well as the point of stimulation.

Figure 5

Spontaneous electrical activity of neuronal clusters on CNT MEA. (A) Voltage traces of spontaneous electrical activity recorded from a CNT electrode. (B) Raster plot of the spontaneous spiking activity in several CNT electrodes. Activity patterns are characterized by bursting events; short time windows (several hundreds of milliseconds) of rapid collective neuronal firing, which are followed by long intervals (seconds) of sporadic firing. For further details see Shein et al. (2009).

Figure 6

(A) A flexible CNT-based MEA. Inset: flexible CNT-based MEA designed for in vivo applications. (B) Evoked electrical activity recorded from an embryonic chick retina (day 14) by a CNT electrode (one out of sixteen 50 μm diameter electrodes in the array) using a biphasic anodic first pulse of 20 nC. Retina was flattened on the flexible CNT MEA with retinal ganglion cells layer facing down. The large signal at t = 0 (marked with arrow) is an artifact of the stimulation. Spontaneous activity prior to stimulation is marked with asterisks.