Long-Term Neural Recording Performance of PEDOT/CNT/Dexamethasone-Coated Electrode Array Implanted in Visual Cortex of Rats

Abstract

Implantable neural electrode arrays can be inserted in the brain to provide single-cell electrophysiology recording for neuroscience research and brain–machine interface applications. However, maintaining signal quality over time is complicated by inflammatory tissue responses and degradation of electrode materials. Organic electrode coatings offer a solution by enhancing recording and stimulation capabilities, including reduced impedance, increased charge injection capacity, and the ability to incorporate and release anti-inflammatory drugs. Herein, acid-functionalized multiwalled carbon nanotubes (CNTs) loaded with dexamethasone (Dex) are incorporated into poly(3,4-ethylendioxythiophene) (PEDOT) as electrode coatings. The electrochemical stability and recording performance of the PEDOT/CNT/Dex coating over an extended period of ≈18 months are investigated. Cyclic voltammetry (CV) stimulation is used to release Dex in half of the recording sites during the first 11 days of implantation to reduce the acute inflammation. The PEDOT/CNT/Dex-coated floating microelectrode arrays demonstrate stable in vivo electrode impedance and successful detection of visually evoked neural activity from the rat visual cortex even at chronic time points. Additionally, the CV-stimulated sites exhibit higher single-unit (SU) recording yield, amplitudes, and signal-to-noise ratio compared to unstimulated sites. These results highlight the potential of anti-inflammatory treatments to improve the quality and longevity of chronic neural recordings.