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Title: Electrochemical and biological performance of chronically stimulated conductive hydrogel electrodes
Authors: Dalrymple, Ashley
Robles, Ulises
Huynh, Mario
Nayagam, Bryony
Green, Rylie
Poole-Warren, Laura
Fallon, James
Shepherd, Robert
Keywords: Electrical stimulation
Neural prosthesis
Conductive hydrogel
Tissue response
Cochlear implants
Issue Date: Mar-2020
Publisher: IOP Publishing
Citation: Dalrymple, A. N., U. A. Aregueta Robles, M. Huynh, B. A. Nayagam, R. Green, L. A. Poole-Warren, J. B. Fallon, and R. K. Shepherd. 2020. Electrochemical and biological performance of chronically stimulated conductive hydrogel electrodes. Journal of Neural Engineering: [epub ahead of print].
Abstract: OBJECTIVE: Evaluate electrochemical properties, biological response, and surface characterization of a conductive hydrogel (CH) coating following chronic in vivo stimulation. APPROACH: Coated CH or uncoated smooth platinum (Pt) electrode arrays were implanted into the cochlea of rats and stimulated over a 5 week period with more than 57 million biphasic current pulses. Electrochemical impedance spectroscopy (EIS), charge storage capacity (CSC), charge injection limit (CIL), and voltage transient (VT) impedance were measured on the bench before and after stimulation, and in vivo during the stimulation program. Electrically-evoked auditory brainstem responses were recorded to monitor neural function. Following explant, the cochleae were examined histologically and electrodes were examined using scanning electron microscopy. MAIN RESULTS: CH coated electrodes demonstrated a bench-top electrochemical advantage over Pt electrodes before and after the electrical stimulation program. In vivo, CH coated electrodes also had a significant advantage over Pt electrodes throughout the stimulation program, exhibiting higher CSC (p = 0.002), larger CIL (p = 0.002), and lower VT impedance (p < 0.001). The CH cohort exhibited a greater tissue response (p = 0.003) with small deposits of particulate material within the tissue capsule. There was no loss in auditory neuron density or change in neural response thresholds in any cochleae. SEM examination of the electrode surface revealed that most CH electrodes exhibited some coating loss; however, there was no evidence of corrosion in the underlying Pt. SIGNIFICANCE: CH coated electrodes demonstrated significant electrochemical advantages on the bench-top and in vivo and maintained neural function despite an increased tissue response and coating loss. While further research is required to understand the cause of the coating loss, CH electrodes provide promise for use in neural prostheses.
URI: http://repository.bionicsinstitute.org:8080/handle/123456789/392
ISSN: 1741-2552
Appears in Collections:Bionic Hearing Research Publications

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