Conducting‐Polymer Nanotubes Improve Electrical Properties,Mechanical Adhesion,Neural Attachment,and Neurite Outgrowth of Neural Electrodes |
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Authors: | Mohammad Reza Abidian Joseph M. Corey Daryl R. Kipke David C. Martin |
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Affiliation: | 1. Department of Biomedical Engineering, The University of Michigan 1101 Beal Ave., Ann Arbor, MI 48109 (USA);2. Department of Neurology, The University of Michigan Ann Arbor, MI 48109 (USA);3. Department of Materials Science and Engineering, Macromolecular Science and Engineering, and Biomedical Engineering Ann Arbor, MI 48109 (USA);4. Present address: Karl W. Boer and Chair Materials Science and Engineering, The University of Delaware 201C Dupont Hall, Newark, DE 19716 (USA) |
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Abstract: | An in vitro comparison of conducting‐polymer nanotubes of poly(3,4‐ethylenedioxythiophene) (PEDOT) and poly(pyrrole) (PPy) and to their film counterparts is reported. Impedance, charge‐capacity density (CCD), tendency towards delamination, and neurite outgrowth are compared. For the same deposition charge density, PPy films and nanotubes grow relatively faster vertically, while PEDOT films and nanotubes grow more laterally. For the same deposition charge density (1.44 C cm?2), PPy nanotubes and PEDOT nanotubes have lower impedance (19.5 ± 2.1 kΩ for PPy nanotubes and 2.5 ± 1.4 kΩ for PEDOT nanotubes at 1 kHz) and higher CCD (184 ± 5.3 mC cm?2 for PPy nanotubes and 392 ± 6.2 mC cm?2 for PEDOT nanotubes) compared to their film counterparts. However, PEDOT nanotubes decrease the impedance of neural‐electrode sites by about two orders of magnitude (bare iridium 468.8 ± 13.3 kΩ at 1 kHz) and increase capacity of charge density by about three orders of magnitude (bare iridium 0.1 ± 0.5 mC cm?2). During cyclic voltammetry measurements, both PPy and PEDOT nanotubes remain adherent on the surface of the silicon dioxide while PPy and PEDOT films delaminate. In experiments of primary neurons with conducting‐polymer nanotubes, cultured dorsal root ganglion explants remain more intact and exhibit longer neurites (1400 ± 95 µm for PPy nanotubes and 2100 ± 150 µm for PEDOT nanotubes) than their film counterparts. These findings suggest that conducting‐polymer nanotubes may improve the long‐term function of neural microelectrodes. |
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Keywords: | bioelectronics conducting polymers nanotubes neural electrodes neurite |
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