Nanocomposites for Neural Interfaces

Abstract

ABSTRACTWe have fabricated micro-probes consisting of gold microelectrode sites (500 μm long and 12 μm wide) modified with conductive polymers and carbon nanotubes to achieve intimate contact with the nervous system. The fabrication process includes photolithography, electroplating and micromachining techniques. In order to obtain a high quality neural contact, we have investigated the preparation and characterization of neural interface materials. Electrochemical polymerization using potentiostatic and galvanostatic methods was used to optimize the surface of the metal electrode sites. Scanning electron microscopy (SEM), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) were used to study the surface morphology, electrochemical properties, and stability of electrodeposited polymers. Cytotoxicity tests using fibroblasts and Schwann cells were performed to evaluate the biocompatibility of the micro-probes and neural interface materials. Dorsal root ganglion (DRG) in vitro preparation was used to evaluate neuronal cell cell adhesion to the electrode. Polypyrrole (PPy) and poly(3,4-ethylendioxythiophene) (EDOT) with various thicknesses and dopants were deposited onto microelectrode sites from aqueous solution. Our results demonstrate that we can control the morphology, size and electrical properties of PPy and PEDOT by changing the polymerization conditions and adding dopant structures, such as chloride and carbon nanotubes (CNT). It was observed that the addition of carbon nanotubes favors the formation of nodules and increases the surface roughness. Also, electrochemical impedance spectroscopy revealed that conductive polymer composites lower the impedance of gold microelectrodes by three orders of magnitude. We found that PPy and PEDOT carbon nanotubes composite coated electrodes maintain intimate contact with axons. Using these conductive polymer composites, high quality nerve spike signals can be detected and electrical stimulation of axons can be achieved.