Cortical Histopathology following Stimulation with Metallic and Carbon Electrodes; pp. 126–141

Bernstein, J.J.; Johnson, P. F.; Hench, Larry L.; Hunter, G.; Dawson, W W

doi:10.1159/000125579

Cited by 21 publications

(3 citation statements)

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“…While both are noble metals, gold and platinum have different resistivities, equating in lower impedance values for gold. They will also behave differently when stimulated, with higher safe charge densities available to platinum than to gold [39]. This being said, the impedance values of the stimulated and nonstimulated cell-free electrodes were comparable, implying no gross increase in electrode surface area as would be associated with electrode corrosion.…”

Section: Cell Cover and Electrical Stimulation Studymentioning

confidence: 99%

Anin vitromodel for investigating impedance changes with cell growth and electrical stimulation: implications for cochlear implants

et al. 2004

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The impedance of stimulating electrodes used in cochlear implants and other neural prostheses often increases post-implantation, and is thought to be due to fibrous tissue encapsulation of the electrode array. Increased impedance results in higher power requirements to stimulate target neurons at set charge densities. We developed an in vitro model to investigate the electrode-tissue interface in a highly controlled environment. This model was tested using three cell types, with and without charge-balanced biphasic electrical stimulation. Under standard tissue culture conditions, a monolayer of cells was grown over the electrode surface. Electrode impedance increased in proportion to the extent of cell coverage of the electrode. Cell type was a significant factor in the amount of impedance increase, with kidney epithelial cells (MDCK) creating the greatest impedance, followed by dissociated rat skin fibroblasts and then macrophages (J774). The application of electrical stimulation to cell-covered electrodes caused impedance fluctuations similar to that seen in vivo, with a lowering of impedance immediately following stimulation, and a recovery to pre-stimulation levels during inactive periods. Examination of these electrodes suggests that the stimulation-induced impedance changes were due to the amount of cell cover over the electrodes. This in vitro technique accurately models the changes in impedance observed with neural prostheses in vivo, and shows the close relationship between impedance and tissue coverage adjacent to the electrode surface. We believe that this in vitro approach holds great promise to further our knowledge of the mechanisms contributing to electrode impedance.

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Section: Cell Cover and Electrical Stimulation Studymentioning

confidence: 99%

Anin vitromodel for investigating impedance changes with cell growth and electrical stimulation: implications for cochlear implants

et al. 2004

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“…Rh, which was the only material essen tially undamaged during stimulation of 0.1 A/cm2 has been shown toxic to tissue even without stimulation [2], Since a safety factor is desired in chronic electrode implants, the safe use level of the materials tested is substantially lower than the minimum test current density of 0.1 A/cm'2.…”

Section: Discussionmentioning

confidence: 94%

“…The histological and physiological re sults are reported in companion papers [2,8]. The effect of charge trans fer on selected candidate metallic electrode materials is presented below.…”

Section: Introductionmentioning

confidence: 99%

An <i>in vitro </i>Analysis of Metal Electrodes for Use in the Neural Environment

Johnson

Hench²

1977

Brain Behav Evol

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The results of evaluation of the corrosion response of Pt, Au, Rh, Ir, Pt-10% Ir and Pt-10% Rh electrodes subjected to bipolar current pulses of 0.1 and 1.0 A/geom. cm² in a simulated neural environment are reported. The criteria for evaluation include the extent and morphology of material removal and corrosion product formation. The chemical changes on the electrode surface and in the test electrolyte are also evaluated. Modified potentiographic methods were developed which monitor interface conditions of the electrodes during chronic, long-term bi-phasic current passage. Under the test conditions established by the neural model, evaluation of the corrosion response of the candidate electrode materials shows that Rh was moderately damaged at 1.0 A/geom. cm², while the remaining test electrodes were severely damaged at this current density. While Rh, Ir and Au exhibit corrosion resistance at 0.1 A/geom. cm², damage to all of the test materials preclude their use in any long-term chronic neural prosthetic implant under the simulated stimulation parameters of the tests. The relative corrosion resistance of the test electrode materials is related to the adherence and coherence of the corrosion product produced on the electrode surface during the first few hundred hours of stimulation. Analysis of the voltage response of the electrodes to current passage provides a means of monitoring the nucleation and growth of the corrosion product.

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Materials for Implantable Electrodes and Electronic Devices

Campbell

Jones

2006

Materials Science and Technology

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Cortical Histopathology following Stimulation with Metallic and Carbon Electrodes; pp. 126–141

Cited by 21 publications

References 0 publications

Anin vitromodel for investigating impedance changes with cell growth and electrical stimulation: implications for cochlear implants

Anin vitromodel for investigating impedance changes with cell growth and electrical stimulation: implications for cochlear implants

An <i>in vitro </i>Analysis of Metal Electrodes for Use in the Neural Environment

Materials for Implantable Electrodes and Electronic Devices

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