Biosensors 2015, 5(4), 618-646; doi:10.3390/bios5040618
In Vivo Electrochemical Analysis of a PEDOT/MWCNT Neural Electrode Coating
1
Department of Bioengineering, University of Pittsburgh, 5056 Biomedical Science Tower 3, 3501 Fifth Avenue, Pittsburgh, PA 15213, USA
2
Center for the Neural Basis of Cognition, University of Pittsburgh, Pittsburgh, PA 15260, USA
3
McGowan Institute for Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA 15260, USA
4
NeuroTech Center of the University of Pittsburgh Brain Institute, Pittsburgh, PA 15260, USA
*
Author to whom correspondence should be addressed.
Academic Editor: Hargsoon Yoon
Received: 18 August 2015 / Revised: 23 September 2015 / Accepted: 30 September 2015 / Published: 13 October 2015
(This article belongs to the Special Issue Neural Sensing and Interfacing Technology)
Abstract
Neural electrodes hold tremendous potential for improving understanding of brain function and restoring lost neurological functions. Multi-walled carbon nanotube (MWCNT) and dexamethasone (Dex)-doped poly(3,4-ethylenedioxythiophene) (PEDOT) coatings have shown promise to improve chronic neural electrode performance. Here, we employ electrochemical techniques to characterize the coating in vivo. Coated and uncoated electrode arrays were implanted into rat visual cortex and subjected to daily cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) for 11 days. Coated electrodes experienced a significant decrease in 1 kHz impedance within the first two days of implantation followed by an increase between days 4 and 7. Equivalent circuit analysis showed that the impedance increase is the result of surface capacitance reduction, likely due to protein and cellular processes encapsulating the porous coating. Coating’s charge storage capacity remained consistently higher than uncoated electrodes, demonstrating its in vivo electrochemical stability. To decouple the PEDOT/MWCNT material property changes from the tissue response, in vitro characterization was conducted by soaking the coated electrodes in PBS for 11 days. Some coated electrodes exhibited steady impedance while others exhibiting large increases associated with large decreases in charge storage capacity suggesting delamination in PBS. This was not observed in vivo, as scanning electron microscopy of explants verified the integrity of the coating with no sign of delamination or cracking. Despite the impedance increase, coated electrodes successfully recorded neural activity throughout the implantation period. View Full-TextKeywords:
interface; neural prosthesis; drug release; controlled drug release; electroactive polymer; nanocomposite
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).
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MDPI and ACS Style
Alba, N.A.; Du, Z.J.; Catt, K.A.; Kozai, T.D.Y.; Cui, X.T. In Vivo Electrochemical Analysis of a PEDOT/MWCNT Neural Electrode Coating. Biosensors 2015, 5, 618-646.
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