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In Vivo Electrochemical Analysis of a PEDOT/MWCNT Neural Electrode Coating.

Alba NA, Du ZJ, Catt KA, Kozai TD, Cui XT - Biosensors (Basel) (2015)

Bottom Line: 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.Some coated electrodes exhibited steady impedance while others exhibiting large increases associated with large decreases in charge storage capacity suggesting delamination in PBS.Despite the impedance increase, coated electrodes successfully recorded neural activity throughout the implantation period.

View Article: PubMed Central - PubMed

Affiliation: Department of Bioengineering, University of Pittsburgh, 5056 Biomedical Science Tower 3, 3501 Fifth Avenue, Pittsburgh, PA 15213, USA. nicolasaalba@gmail.com.

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.

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SEM images of representative uncoated (a) and PEDOT/MWCNT/Dex coated (b) electrode tips extracted from the brain after 11 days. Tips were cleaned using trypsinization and dried before imaging. Note intact coating with no visible cracks or spallation, and the presence of a dense biological film overlaying the coating. Scale bars = 3 µm.
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biosensors-05-00618-f005: SEM images of representative uncoated (a) and PEDOT/MWCNT/Dex coated (b) electrode tips extracted from the brain after 11 days. Tips were cleaned using trypsinization and dried before imaging. Note intact coating with no visible cracks or spallation, and the presence of a dense biological film overlaying the coating. Scale bars = 3 µm.

Mentions: Scanning electron microscope images of representative explanted electrodes are shown in Figure 5, including uncoated (Figure 5a) and coated (Figure 5b) examples. Uncoated explanted electrodes demonstrated dimensions and surface texture visually consistent with pre-implant micrographs. Coated explanted electrodes exhibited intact coatings with no visible cracks, spallation, or removal in over 85% of the electrodes examined. Tissue ingrowth was also observed on the surface of the intact coated explanted electrodes, penetrating and occluding the open lattice structure of the coating. We were unable to determine the composition of this residue due to the preparatory steps performed for high resolution SEM.


In Vivo Electrochemical Analysis of a PEDOT/MWCNT Neural Electrode Coating.

Alba NA, Du ZJ, Catt KA, Kozai TD, Cui XT - Biosensors (Basel) (2015)

SEM images of representative uncoated (a) and PEDOT/MWCNT/Dex coated (b) electrode tips extracted from the brain after 11 days. Tips were cleaned using trypsinization and dried before imaging. Note intact coating with no visible cracks or spallation, and the presence of a dense biological film overlaying the coating. Scale bars = 3 µm.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4697137&req=5

biosensors-05-00618-f005: SEM images of representative uncoated (a) and PEDOT/MWCNT/Dex coated (b) electrode tips extracted from the brain after 11 days. Tips were cleaned using trypsinization and dried before imaging. Note intact coating with no visible cracks or spallation, and the presence of a dense biological film overlaying the coating. Scale bars = 3 µm.
Mentions: Scanning electron microscope images of representative explanted electrodes are shown in Figure 5, including uncoated (Figure 5a) and coated (Figure 5b) examples. Uncoated explanted electrodes demonstrated dimensions and surface texture visually consistent with pre-implant micrographs. Coated explanted electrodes exhibited intact coatings with no visible cracks, spallation, or removal in over 85% of the electrodes examined. Tissue ingrowth was also observed on the surface of the intact coated explanted electrodes, penetrating and occluding the open lattice structure of the coating. We were unable to determine the composition of this residue due to the preparatory steps performed for high resolution SEM.

Bottom Line: 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.Some coated electrodes exhibited steady impedance while others exhibiting large increases associated with large decreases in charge storage capacity suggesting delamination in PBS.Despite the impedance increase, coated electrodes successfully recorded neural activity throughout the implantation period.

View Article: PubMed Central - PubMed

Affiliation: Department of Bioengineering, University of Pittsburgh, 5056 Biomedical Science Tower 3, 3501 Fifth Avenue, Pittsburgh, PA 15213, USA. nicolasaalba@gmail.com.

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.

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