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

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. In this study, acid-functionalized multi-walled carbon nanotubes (CNTs) loaded with dexamethasone (Dex) were incorporated into poly (3,4-ethylendioxythiophene) (PEDOT) as electrode coatings. We investigated the electrochemical stability and recording performance of the PEDOT/CNT/Dex coating over an extended period of approximately 18 months. Cyclic voltammetric (CV) stimulation was used to trigger Dex release 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 demonstrated 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 exhibited higher single-unit 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.