Electropermeabilization of Adherent Cells with Cochlear Implant Electrical Stimulation in vitro

Abstract

Cochlear implant stimulation creates a reduction in electrode impedance that returns to pre-stimulation levels following cessation of stimulation and is presumed to be associated with the fibrous tissue covering over the electrode array. This study assessed the possibility that transitory impedance reduction originates from a change in the membrane permeability of cells on the electrode (electropermeabilization). These changes can be recorded using the dye propidium iodide, which fluoresces upon entry into the leaky cell. The in vitro model used showed impedance reduction and dye uptake into adherent cells overlying planar gold electrodes stimulated with as little as 5 min of clinically relevant cochlear implant stimulation. The delayed additions of propidium iodide showed a similar dye uptake to those groups with concurrent dye addition, suggesting the electropermeabilization was not reversible. Further understanding of the mechanisms behind these impedance and cell permeability changes with cochlear implant electrical stimulation may provide opportunities for creating long-lasting reductions in electrode impedance.

Immunohistological and Ultrastructural Study of the Inflammatory Response to Perforated Polyimide Cortical Implants: Mechanisms Underlying Deterioration of Electrophysiological Recording Quality

“…Attenuation of FP amplitude at the surface of a MEA implant could occur by a number of mechanisms: (A) a “blocking” ion bi-layer formed at the metal electrode surface and the extracellular ionic solution of the brain ( McAdams et al, 2006 ), (B) a self-assembled biofouling layers on the electrode surface ( Sommakia et al, 2009 , 2014a ; Malaga et al, 2016 ), and (C) by increased impedance produced by cells adhering to the electrode surfaces as demonstrated for cochlear implants ( Newbold et al, 2010 , 2014 ). Based on our TEM and immunohistological observations it is conceivable that in cortical brain implants, microglia and possibly astrocyte that adhere directly to the electrode may play a dominant role in electrodes deterioration and subsequent insulation.…”

Electrophysiological status indexed by early changes in impedance after cochlear implantation: A literature review

“…Therefore, by observing the variation in impedance, information about intracochlear changes in the surrounding encompassing electrodes can be predicted. [3][4][5][6] Impedance is also a useful tool for the optimization of most comfortable levels in terms of stimulus and settings for the cochlear implant. 7 In addition, impedance can be a potential biomarker highly correlated with imbalance disorder 6 and/or performance of hearing as well speech after the surgery.…”