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Title: Electrochemical and biological characterization of thin-film platinum-iridium alloy electrode coatings: a chronic in vivo study
Authors: Dalrymple, Ashley
Huynh, Mario
Nayagam, Bryony
Lee, Curtis
Weiland, Greg
Petrossians, Artin
Whalen, John
Fallon, James
Shepherd, Robert
Keywords: Electrical stimulation
Neural prosthesis
Electrodeposited Pt-Ir
Tissue response
Cochlear implants
Electrode impendance
Electrode neural interface
Issue Date: May-2020
Publisher: IOP Publishing
Citation: Dalrymple, A. N., M. Huynh, B. A. Nayagam, C. Lee, G. R. Weiland, A. Petrossians, J. J. Whalen Iii, J. B. Fallon, and R. K. Shepherd. 2020. Electrochemical and biological characterization of thin-film platinum-iridium alloy electrode coatings: a chronic in vivo study. Journal of Neural Engineering: [epub ahead of print].
Abstract: OBJECTIVE: To evaluate the electrochemical properties, biological response, and surface characterization of an electrodeposited Platinum-Iridium (Pt-Ir) electrode coating on cochlear implants subjected to chronic stimulation in vivo. APPROACH: Electrochemical impedance spectroscopy (EIS), charge storage capacity (CSC), charge injection limit (CIL), and voltage transient (VT) impedance were measured bench-top before and after implant and in vivo. Coated Pt-Ir and uncoated Pt electrode arrays were implanted into cochlea of normal hearing rats and stimulated for ~4 hours/day, 5 days/week for 5 weeks. Neural function was monitored using electrically-evoked auditory brainstem responses. After explant, the electrode surfaces were assessed, and cochleae examined histologically. MAIN RESULTS: When measured on bench-top before and after stimulation, Pt-Ir coated electrodes had significantly lower VT impedance (p < 0.001) and significantly higher CSC (p < 0.001) and CIL (p < 0.001) compared to uncoated Pt electrodes. In vivo, the CSC and CIL of Pt-Ir were significantly higher than Pt throughout the implantation period (p = 0.047 and p < 0.001, respectively); however, the VT impedance (p = 0.3) was not. There was no difference in foreign body response between material cohorts, although cochleae implanted with coated electrodes contained small deposits of Pt-Ir. There was no evidence of increased neural loss or loss of neural function in either group. Surface examination revealed no Pt corrosion on any electrodes. SIGNIFICANCE: Electrodeposited Pt-Ir electrodes demonstrated significant improvements in electrochemical performance on the bench-top and in vivo compared to uncoated Pt. Neural function and tissue response to Pt-Ir electrodes were not different from uncoated Pt, despite small deposits of Pt-Ir in the tissue capsule. Electrodeposited Pt-Ir coatings offer promise as an improved electrode coating for active neural prostheses.
URI: http://repository.bionicsinstitute.org:8080/handle/123456789/398
ISSN: 1741-2552
Appears in Collections:Bionic Hearing Research Publications

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