Over-pulsing degrades activated iridium oxide films used for intracortical neural stimulation

Cogan, Stuart F.; Guzelian, A. A.; Agnew, William F.; Yuen, T.G.H.; McCreery, Douglas B.

doi:10.1016/j.jneumeth.2004.02.019

Cited by 192 publications

(154 citation statements)

References 24 publications

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“…An electroactive area will measure the total electrochemically functional electrode area including its roughness (regions that are non-or poorly conducting will not be 6 6…”

Section: Resultsmentioning

confidence: 99%

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Optical and Electrochemical Methods for Determining the Effective Area and Charge Density of Conducting Polymer Modified Electrodes for Neural Stimulation

et al. 2014

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Neural stimulation is used in the cochlear implant, bionic eye, and deep brain stimulation, which involves implantation of an array of electrodes into a patient's brain. The current passed through the electrodes is used to provide sensory queues or reduce symptoms associated with movement disorders and increasingly for psychological and pain therapies. Poor control of electrode properties can lead to suboptimal performance; however, there are currently no standard methods to assess them, including the electrode area and charge density. Here we demonstrate optical and electrochemical methods for measuring these electrode properties and show the charge density is dependent on electrode geometry. This technique highlights that materials can have widely different charge densities but also large variation in performance. Measurement of charge density from an electroactive area may result in new materials and electrode geometries that improve patient outcomes and reduce side effects. AbstractNeural stimulation is used in the cochlear implant, bionic eye and deep brain stimulation which involves implantation of an array of electrodes into a patient's brain. The current passed through the electrodes is used to provide sensory queues or reduce symptoms associated with movement disorders and increasingly for psychological and pain therapies. Poor control of electrode properties can lead to sub-optimal performance; however there are currently no standard methods to assess them, including the electrode area and charge density. Here we demonstrate optical and electrochemical methods for measuring these electrode properties and show the charge density is dependent on electrode geometry. This technique highlights that materials can have widely different charge densities, but also large variation in performance. Measurement of charge density from an electroactive area may result in new materials and electrode geometries that improve patient outcomes and reduce side-effects.

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“…An electroactive area will measure the total electrochemically functional electrode area including its roughness (regions that are non-or poorly conducting will not be 6 6…”

Section: Resultsmentioning

confidence: 99%

“…DBS electrodes are currently all platinum, and the charge density is usually assessed by cyclic voltammetry 5,6 . Under this condition, the charge density is related to the capacitance current generated at the electrode-solution interface.…”

Section: Introductionmentioning

confidence: 99%

Optical and Electrochemical Methods for Determining the Effective Area and Charge Density of Conducting Polymer Modified Electrodes for Neural Stimulation

et al. 2014

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“…More recently, a range of new electrode materials and coatings have been proposed: Iridium oxide is a material able to undergo Faradaic electrochemical reactions, resulting in a much larger charge capacity than pure planar or roughened metal electrodes [7] but its long term stability issues, particularly at high current injection levels, limit its potential for chronic implantation [8][9][10][11].…”

Section: Introductionmentioning

confidence: 99%

Conducting polymer coated neural recording electrodes

et al. 2012

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Neural recording electrodes suffer from poor signal to noise ratio, charge density, biostability and biocompatibility. This paper investigates the ability of conducting polymer coated electrodes to record acute neural response in a systematic manner, allowing in depth comparison of electrochemical and electrophysiological response. Approach. Polypyrrole (Ppy) and poly-3,4-ethylenedioxythiophene (PEDOT) doped with sulphate (SO4) or para-toluene sulfonate (pTS) were used to coat iridium neural recording electrodes. Detailed electrochemical and electrophysiological investigations were undertaken to compare the effect of these materials on acute in vivo recording. Main results. A range of charge density and impedance responses were seen with each respectively doped conducting polymer. All coatings produced greater charge density than uncoated electrodes, while PEDOT-pTS, PEDOT-SO 4 and Ppy-SO4 possessed lower impedance values at 1 kHz than uncoated electrodes. Charge density increased with PEDOT-pTS thickness and impedance at 1 kHz was reduced with deposition times up to 45 s. Stable electrochemical response after acute implantation inferred biostability of PEDOT-pTS coated electrodes while other electrode materials had variable impedance and/or charge density after implantation indicative of a protein fouling layer forming on the electrode surface. Recording of neural response to white noise bursts after implantation of conducting polymer-coated electrodes into a rat model inferior colliculus showed a general decrease in background noise and increase in signal to noise ratio and spike count with reduced impedance at 1 kHz, regardless of the specific electrode coating, compared to uncoated electrodes. A 45 s PEDOT-pTS deposition time yielded the highest signal to noise ratio and spike count. Significance. A method for comparing recording electrode materials has been demonstrated with doped conducting polymers. PEDOT-pTS showed remarkable low fouling during acute implantation, inferring good biostability. Electrode impedance at 1 kHz was correlated with background noise and inversely correlated with signal to noise ratio and spike count, regardless of coating. These results collectively confirm a potential for improvement of neural electrode systems by coating with conducting polymers. 2013 IOP Publishing Ltd.

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“…Perceptual threshold measurements obtained in blind humans have varied widely, although 0.5 μC/phase is reasonably good representation of the collective results [8]. However, charge densities of >2000 μC/cm 2 can result in substantial damage to the electrode and tissue [9,10]. Thus, large electrodes (>175 μm diameter) are required to supply the needed charge to minimize charge density and the risk of electrode or tissue damage.…”

Section: Introductionmentioning

confidence: 99%

Tissue engineering applied to the retinal prosthesis: Neurotrophin-eluting polymeric hydrogel coatings

Winter

Gokhale

Jensen

et al. 2008

Materials Science and Engineering: C

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Several groups are developing visual prostheses to aid patients with vision loss. While these devices have shown some success in the clinic, they are severely limited by poor resolution, and in many cases have as few as 15 electrodes. Pixel density is poor because high stimulation thresholds require large electrodes to minimize charge density that would otherwise damage the electrode and tissue. A significant contributor to high stimulation threshold requirements is poor biocompatibility. We investigated the application of one system popular in tissue engineering, drug-releasing hydrogels, as a mechanism to improve the tissue-electrode interface. Hydrogels studied (i.e., PEGPLA photocrosslinkable polymers) released neurotrophic factors (i.e., BDNF) known to promote neuron survival and neurite extension in the retina. Hydrogels were examined in co-culture with retinal explants for 7 and 14 days, at which time neurite extension and neurite density was measured. Neurite extension was enhanced in samples exposed to BDNF-releasing hydrogels at 7 days; however, these increases were absent by day 14 suggesting declining drug release. Thus, PEGPLA hydrogels are excellent candidates for short-term (< 14 day) acute release of therapeutic factors in the retina, but will require additional modifications for application with neural prostheses. Additionally, these results suggest that the effects of neurotrophic factors are short-lived in the absence of additional support cues, and tissue engineering systems employing such factors may only produce transient benefits to the patient.

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Over-pulsing degrades activated iridium oxide films used for intracortical neural stimulation

Cited by 192 publications

References 24 publications

Optical and Electrochemical Methods for Determining the Effective Area and Charge Density of Conducting Polymer Modified Electrodes for Neural Stimulation

Optical and Electrochemical Methods for Determining the Effective Area and Charge Density of Conducting Polymer Modified Electrodes for Neural Stimulation

Conducting polymer coated neural recording electrodes

Tissue engineering applied to the retinal prosthesis: Neurotrophin-eluting polymeric hydrogel coatings

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