title: In Vivo Electrochemical Analysis of a PEDOT/MWCNT Neural Electrode Coating.
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.
authors.affiliation: Department of Bioengineering, University of Pittsburgh, 5056 Biomedical Science Tower 3, 3501 Fifth Avenue, Pittsburgh, PA 15213, USA. nicolasaalba@gmail.com.|Center for the Neural Basis of Cognition, University of Pittsburgh, Pittsburgh, PA 15260, USA. nicolasaalba@gmail.com.|McGowan Institute for Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA 15260, USA. nicolasaalba@gmail.com.
authors.forename: Nicolas A
authors.initials: NA
authors.lastname: Alba
authors.affiliation: Department of Bioengineering, University of Pittsburgh, 5056 Biomedical Science Tower 3, 3501 Fifth Avenue, Pittsburgh, PA 15213, USA. duzhanhong@gmail.com.|Center for the Neural Basis of Cognition, University of Pittsburgh, Pittsburgh, PA 15260, USA. duzhanhong@gmail.com.|McGowan Institute for Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA 15260, USA. duzhanhong@gmail.com.
authors.forename: Zhanhong J
authors.initials: ZJ
authors.lastname: Du
authors.affiliation: Department of Bioengineering, University of Pittsburgh, 5056 Biomedical Science Tower 3, 3501 Fifth Avenue, Pittsburgh, PA 15213, USA. kaseycatt@gmail.com.
authors.forename: Kasey A
authors.initials: KA
authors.lastname: Catt
authors.affiliation: Department of Bioengineering, University of Pittsburgh, 5056 Biomedical Science Tower 3, 3501 Fifth Avenue, Pittsburgh, PA 15213, USA. tdk18@pitt.edu.|Center for the Neural Basis of Cognition, University of Pittsburgh, Pittsburgh, PA 15260, USA. tdk18@pitt.edu.|McGowan Institute for Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA 15260, USA. tdk18@pitt.edu.|NeuroTech Center of the University of Pittsburgh Brain Institute, Pittsburgh, PA 15260, USA. tdk18@pitt.edu.
authors.forename: Takashi D Y
authors.initials: TD
authors.lastname: Kozai
authors.affiliation: Department of Bioengineering, University of Pittsburgh, 5056 Biomedical Science Tower 3, 3501 Fifth Avenue, Pittsburgh, PA 15213, USA. xic11@pitt.edu.|Center for the Neural Basis of Cognition, University of Pittsburgh, Pittsburgh, PA 15260, USA. xic11@pitt.edu.|McGowan Institute for Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA 15260, USA. xic11@pitt.edu.
authors.forename: X Tracy
authors.initials: XT
authors.lastname: Cui
mesh_terms: D000818:Animals; D000893:Anti-Inflammatory Agents / Q000737:chemistry*; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000737:chemistry*; D020099:Coated Materials, Biocompatible / Q000737:chemistry*; D003907:Dexamethasone / Q000737:chemistry*; D017097:Electric Impedance; D055664:Electrochemical Techniques; D008297:Male; D008839:Microelectrodes; D037742:Nanotubes, Carbon / Q000737:chemistry*; D058117:Neural Prostheses; D011108:Polymers / Q000737:chemistry*; D051381:Rats; D020318:Rats, Long-Evans; D014793:Visual Cortex / Q000502:physiology* / Q000601:surgery
chemical_list: D000893:Anti-Inflammatory Agents; D019086:Bridged Bicyclo Compounds, Heterocyclic; D020099:Coated Materials, Biocompatible; D037742:Nanotubes, Carbon; D011108:Polymers; C121383:poly(3,4-ethylene dioxythiophene); D003907:Dexamethasone
keywords: controlled drug release; drug release; electroactive polymer; interface; nanocomposite; neural prosthesis