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Ramesh V, Johny J, Jakobi J, Stuckert R, Rehbock C, Barcikowski S. Platinum-Iridium Alloy Nanoparticle Coatings Produced by Electrophoretic Deposition Reduce Impedance in 3D Neural Electrodes. Chemphyschem 2024; 25:e202300623. [PMID: 38842467 DOI: 10.1002/cphc.202300623] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2023] [Revised: 05/14/2024] [Accepted: 05/28/2024] [Indexed: 06/07/2024]
Abstract
Platinum-based neural electrodes, frequently alloyed with Ir or W, are routinely used to treat neurological disorders. However, their performance is impaired by an increase in impedance that compromises long-term implant functionality. Though there are multiple coating techniques available to address this issue, electrode, and base material often exhibit a compositional mismatch, which impairs mechanical stability and may lead to toxicological side effects. In this work, we coated Pt wire electrodes with ligand-free electrostatically stabilized colloidal Pt90Ir10, Pt90W10, and Pt50W50 alloy nanoparticles (NPs) matching electrode compositions using electrophoretic deposition (EPD) with direct-current (DC) and pulsed-DC fields in aqueous medium. The generated alloy NPs exhibit a solid solution structure as evidenced by HR-TEM-EDX and XRD, though additional WOx phases were identified in the Pt50W50 samples. Consequently, coating efficiency was also impaired in the presence of high W mass fractions in the alloy NPs. Characterization of the NP coatings by cyclic voltammetry and impedance spectroscopy yielded a significant reduction of the impedance in the Pt90Ir10 sample in comparison to the control coated with Pt NPs. The electrochemical surface area (ECSA) of the PtW alloy coatings, on the other hand, was significantly reduced.
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Affiliation(s)
- Vaijayanthi Ramesh
- Technical Chemistry I, University of Duisburg-Essen, Center for Nanointegration Duisburg-Essen (CENIDE), Universitätsstr. 7, 45141, Essen, Germany
| | - Jacob Johny
- Technical Chemistry I, University of Duisburg-Essen, Center for Nanointegration Duisburg-Essen (CENIDE), Universitätsstr. 7, 45141, Essen, Germany
| | - Jurij Jakobi
- Technical Chemistry I, University of Duisburg-Essen, Center for Nanointegration Duisburg-Essen (CENIDE), Universitätsstr. 7, 45141, Essen, Germany
| | - Robert Stuckert
- Technical Chemistry I, University of Duisburg-Essen, Center for Nanointegration Duisburg-Essen (CENIDE), Universitätsstr. 7, 45141, Essen, Germany
| | - Christoph Rehbock
- Technical Chemistry I, University of Duisburg-Essen, Center for Nanointegration Duisburg-Essen (CENIDE), Universitätsstr. 7, 45141, Essen, Germany
| | - Stephan Barcikowski
- Technical Chemistry I, University of Duisburg-Essen, Center for Nanointegration Duisburg-Essen (CENIDE), Universitätsstr. 7, 45141, Essen, Germany
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Duan W, Robles UA, Poole‐Warren L, Esrafilzadeh D. Bioelectronic Neural Interfaces: Improving Neuromodulation Through Organic Conductive Coatings. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2024; 11:e2306275. [PMID: 38115740 PMCID: PMC11251570 DOI: 10.1002/advs.202306275] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/05/2023] [Revised: 11/07/2023] [Indexed: 12/21/2023]
Abstract
Integration of bioelectronic devices in clinical practice is expanding rapidly, focusing on conditions ranging from sensory to neurological and mental health disorders. While platinum (Pt) electrodes in neuromodulation devices such as cochlear implants and deep brain stimulators have shown promising results, challenges still affect their long-term performance. Key among these are electrode and device longevity in vivo, and formation of encapsulating fibrous tissue. To overcome these challenges, organic conductors with unique chemical and physical properties are being explored. They hold great promise as coatings for neural interfaces, offering more rapid regulatory pathways and clinical implementation than standalone bioelectronics. This study provides a comprehensive review of the potential benefits of organic coatings in neuromodulation electrodes and the challenges that limit their effective integration into existing devices. It discusses issues related to metallic electrode use and introduces physical, electrical, and biological properties of organic coatings applied in neuromodulation. Furthermore, previously reported challenges related to organic coating stability, durability, manufacturing, and biocompatibility are thoroughly reviewed and proposed coating adhesion mechanisms are summarized. Understanding organic coating properties, modifications, and current challenges of organic coatings in clinical and industrial settings is expected to provide valuable insights for their future development and integration into organic bioelectronics.
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Affiliation(s)
- Wenlu Duan
- The Graduate School of Biomedical EngineeringUNSWSydneyNSW2052Australia
| | | | - Laura Poole‐Warren
- The Graduate School of Biomedical EngineeringUNSWSydneyNSW2052Australia
- Tyree Foundation Institute of Health EngineeringUNSWSydneyNSW2052Australia
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3
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Muguet I, Maziz A, Mathieu F, Mazenq L, Larrieu G. Combining PEDOT:PSS Polymer Coating with Metallic 3D Nanowires Electrodes to Achieve High Electrochemical Performances for Neuronal Interfacing Applications. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023; 35:e2302472. [PMID: 37385261 DOI: 10.1002/adma.202302472] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2023] [Revised: 05/18/2023] [Accepted: 05/26/2023] [Indexed: 07/01/2023]
Abstract
This study presents a novel approach to improve the performance of microelectrode arrays (MEAs) used for electrophysiological studies of neuronal networks. The integration of 3D nanowires (NWs) with MEAs increases the surface-to-volume ratio, which enables subcellular interactions and high-resolution neuronal signal recording. However, these devices suffer from high initial interface impedance and limited charge transfer capacity due to their small effective area. To overcome these limitations, the integration of conductive polymer coatings, poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) is investigated as a mean of improving the charge transfer capacity and biocompatibility of MEAs. The study combines platinum silicide-based metallic 3D nanowires electrodes with electrodeposited PEDOT:PSS coatings to deposit ultra-thin (<50 nm) layers of conductive polymer onto metallic electrodes with very high selectivity. The polymer-coated electrodes were fully characterized electrochemically and morphologically to establish a direct relationship between synthesis conditions, morphology, and conductive features. Results show that PEDOT-coated electrodes exhibit thickness-dependent improved stimulation and recording performances, offering new perspectives for neuronal interfacing with optimal cell engulfment to enable the study of neuronal activity with acute spatial and signal resolution at the sub-cellular level.
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Affiliation(s)
- Ines Muguet
- LAAS-CNRS, Université de Toulouse, CNRS, 7 avenue du colonel Roche, Toulouse, F-31400, France
| | - Ali Maziz
- LAAS-CNRS, Université de Toulouse, CNRS, 7 avenue du colonel Roche, Toulouse, F-31400, France
| | - Fabrice Mathieu
- LAAS-CNRS, Université de Toulouse, CNRS, 7 avenue du colonel Roche, Toulouse, F-31400, France
| | - Laurent Mazenq
- LAAS-CNRS, Université de Toulouse, CNRS, 7 avenue du colonel Roche, Toulouse, F-31400, France
| | - Guilhem Larrieu
- LAAS-CNRS, Université de Toulouse, CNRS, 7 avenue du colonel Roche, Toulouse, F-31400, France
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4
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Sun T, Tsaava T, Peragine J, Crosfield C, Lopez MF, Modi R, Sharma R, Li C, Sohal H, Chang EH, Rieth L. Flexible IrO x neural electrode for mouse vagus nerve stimulation. Acta Biomater 2023; 159:394-409. [PMID: 36669547 PMCID: PMC10823593 DOI: 10.1016/j.actbio.2023.01.026] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2022] [Revised: 12/26/2022] [Accepted: 01/10/2023] [Indexed: 01/19/2023]
Abstract
Vagus nerve stimulation (VNS) is being actively explored as a treatment for multiple conditions as part of bioelectronic medicine research. Reliable and safe VNS in mouse models is a critical need for understanding mechanisms of these. We report on the development and evaluation of a microfabricated cuff electrode (MouseFlex) constructed of polyimide (PI) and with iridium oxide (IrOx) electrodes that is thermoformed to 86 µm ± 12 µm radius to interface the mouse cervical vagus nerve (r ≈ 50 µm). Innovative bench-top methods were used to evaluate the stimulation stability and electrochemical properties of electrodes. Our aggressive stimulation stability (Stim-Stab) test utilized 1 billion pulses at a 1000 Hz with a current density of 6.28 A/cm2 (1.51 mC/cm2/phase) delivering 3023 × 103 C/cm2 to evaluate electrode lifetimes, and all electrodes remained functional. We also investigated the effects of thermoforming on their impedance, charge storage capacity (CSC), and charge injection capacity (CIC). The modest changes in electrochemical properties indicate that the thermoforming process was well tolerated. Thermoformed electrode safety and efficacy were evaluated in-vivo by performing acute VNS in mice and monitoring their heart and respiration rate as biomarkers. Their electrochemical properties were also measured before, during and after VNS. Bradycardia and bradypnea were reliably induced at stimulation currents of 100 to 200 µA, well below the in-vivo CIC of ∼1250 µA (∼0.5 mC/cm2), supporting their safety and efficacy. The electrode impedance increased and CIC decreased during in-vivo use, but largely reversed these changes in in-vitro testing after enzymatic cleaning, supporting their tolerance for surgical use. STATEMENT OF SIGNIFICANCE: Vagus nerve stimulation (VNS) is a rapidly growing aspect of healthcare and bioelectronic medicine research. Reliable and safe VNS in mice with small diameter (d ≈ 100 µm) nerves has been a challenge due to achieving intimate contact with the nerve, and the stimulation stability of commonly used electrodes. We demonstrate a microfabricated (MouseFlex) cuff electrode constructed of polyimide with IrOx electrodes that is thermoformed to contact the mouse cervical vagus. Bench studies highlight the stimulation stability exceeded 109 pulses at 6.28 A/cm2 and their electrochemical properties were measured before, during, and after bench and nerve stimulation. Nerve stimulation induced bradycardia and bradypnea at currents below the in-vivo charge injection capacity, supporting their safety, efficacy, and tolerance for surgical handling.
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Affiliation(s)
- Tao Sun
- Mechanical & Aerospace Engineering Department, Benjamin M. Statler College of Engineering & Mineral Resources, West Virginia University, Morgantown, WV 26505, United States
| | - Téa Tsaava
- Institute of Bioelectronic Medicine, Feinstein Institutes for Medical Research, Manhasset, New York 11030, United States
| | - Joanne Peragine
- Institute of Bioelectronic Medicine, Feinstein Institutes for Medical Research, Manhasset, New York 11030, United States
| | - Christine Crosfield
- Institute of Bioelectronic Medicine, Feinstein Institutes for Medical Research, Manhasset, New York 11030, United States
| | | | - Romil Modi
- Institute of Bioelectronic Medicine, Feinstein Institutes for Medical Research, Manhasset, New York 11030, United States
| | - Rohit Sharma
- Electrical and Computer Engineering Department, University of Utah, Salt Lake City, UT 84112, United States; Applied Biosensors, Salt Lake City, UT 84115, United States
| | - Chunyan Li
- Institute of Bioelectronic Medicine, Feinstein Institutes for Medical Research, Manhasset, New York 11030, United States
| | | | - Eric H Chang
- Institute of Bioelectronic Medicine, Feinstein Institutes for Medical Research, Manhasset, New York 11030, United States
| | - Loren Rieth
- Mechanical & Aerospace Engineering Department, Benjamin M. Statler College of Engineering & Mineral Resources, West Virginia University, Morgantown, WV 26505, United States.
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Dong M, Coleman HA, Tonta MA, Xiong Z, Li D, Thomas S, Liu M, Fallon JB, Parkington HC, Forsythe JS. Rapid electrophoretic deposition of biocompatible graphene coatings for high-performance recording neural electrodes. NANOSCALE 2022; 14:15845-15858. [PMID: 36259692 DOI: 10.1039/d2nr04421h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
The electrical and biological interfacial properties of invasive electrodes have a significant impact on the performance and longevity of neural recordings in the brain. In this study, we demonstrated rapid electrophoretic deposition and electrochemical reduction of graphene oxide (GO) on metal-based neural electrodes. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and other characterizations confirmed the existence of a uniform and effectively reduced graphene oxide coating. Electrochemically reduced graphene oxide (ErGO) coated Pt/Ir neural electrodes exhibited 15.2-fold increase in charge storage capacity (CSC) and 90% decrease in impedance with only 3.8% increase in electrode diameter. Patch clamp electrophysiology and calcium imaging of primary rat hippocampus neurons cultured on ErGO demonstrated that there was no adverse impact on the functional development of neurons. Immunostaining showed a balanced growth of excitatory and inhibitory neurons, and astrocytes. Acute recordings from the auditory cortex and chronic recordings (19 days) from the somatosensory cortex found ErGO coating improved the performance of neural electrodes in signal-to-noise ratio (SNR) and amplitude of signals. The proposed approach not only provides an in-depth evaluation of the effect of ErGO coating on neural electrodes but also widens the coating methods of commercial neural electrodes.
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Affiliation(s)
- Miheng Dong
- Department of Materials Science and Engineering, Monash Institute of Medical Engineering, Monash University, Clayton, VIC 3800, Australia.
- Monash Suzhou Research Institute, Monash University, Suzhou SIP 250000, China
| | - Harold A Coleman
- Department of Physiology, Biomedicine Discovery Institute, Monash University, Clayton, VIC 3800, Australia
| | - Mary A Tonta
- Department of Physiology, Biomedicine Discovery Institute, Monash University, Clayton, VIC 3800, Australia
| | - Zhiyuan Xiong
- Department of Chemical Engineering, University of Melbourne, Parkville, Victoria, Australia
| | - Dan Li
- Department of Chemical Engineering, University of Melbourne, Parkville, Victoria, Australia
| | - Sebastian Thomas
- Department of Materials Science and Engineering, Monash Institute of Medical Engineering, Monash University, Clayton, VIC 3800, Australia.
| | - Minsu Liu
- Department of Materials Science and Engineering, Monash Institute of Medical Engineering, Monash University, Clayton, VIC 3800, Australia.
- Monash Suzhou Research Institute, Monash University, Suzhou SIP 250000, China
- Foshan (Southern China) Institute for New Materials, Foshan 528200, China
| | - James B Fallon
- The Bionics Institute, East Melbourne, Victoria 3002, Australia
- Medical Bionics Department, University of Melbourne, Parkville, Victoria 3010, Australia
| | - Helena C Parkington
- Department of Physiology, Biomedicine Discovery Institute, Monash University, Clayton, VIC 3800, Australia
| | - John S Forsythe
- Department of Materials Science and Engineering, Monash Institute of Medical Engineering, Monash University, Clayton, VIC 3800, Australia.
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Ertas YN, Ozpolat D, Karasu SN, Ashammakhi N. Recent Advances in Cochlear Implant Electrode Array Design Parameters. MICROMACHINES 2022; 13:1081. [PMID: 35888898 PMCID: PMC9323156 DOI: 10.3390/mi13071081] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/10/2022] [Revised: 06/29/2022] [Accepted: 06/30/2022] [Indexed: 02/04/2023]
Abstract
Cochlear implants are neural implant devices that aim to restore hearing in patients with severe sensorineural hearing impairment. Here, the main goal is to successfully place the electrode array in the cochlea to stimulate the auditory nerves through bypassing damaged hair cells. Several electrode and electrode array parameters affect the success of this technique, but, undoubtedly, the most important one is related to electrodes, which are used for nerve stimulation. In this paper, we provide a comprehensive resource on the electrodes currently being used in cochlear implant devices. Electrode materials, shape, and the effect of spacing between electrodes on the stimulation, stiffness, and flexibility of electrode-carrying arrays are discussed. The use of sensors and the electrical, mechanical, and electrochemical properties of electrode arrays are examined. A large library of preferred electrodes is reviewed, and recent progress in electrode design parameters is analyzed. Finally, the limitations and challenges of the current technology are discussed along with a proposal of future directions in the field.
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Affiliation(s)
- Yavuz Nuri Ertas
- Department of Biomedical Engineering, Erciyes University, Kayseri 38039, Turkey; (D.O.); (S.N.K.)
- ERNAM—Nanotechnology Research and Application Center, Erciyes University, Kayseri 38039, Turkey
| | - Derya Ozpolat
- Department of Biomedical Engineering, Erciyes University, Kayseri 38039, Turkey; (D.O.); (S.N.K.)
- ERNAM—Nanotechnology Research and Application Center, Erciyes University, Kayseri 38039, Turkey
| | - Saime Nur Karasu
- Department of Biomedical Engineering, Erciyes University, Kayseri 38039, Turkey; (D.O.); (S.N.K.)
- ERNAM—Nanotechnology Research and Application Center, Erciyes University, Kayseri 38039, Turkey
| | - Nureddin Ashammakhi
- Institute for Quantitative Health Science and Engineering (IQ) and Department of Biomedical Engineering (BME), Michigan State University, East Lansing, MI 48824, USA
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Almasri RM, Abed AA, Esrafilzadeh D, Mawad D, Poole-Warren LA, Lovell NH. Electromechanical Stability and Transmission Behavior of Transparent Conductive Films for Biomedical Optoelectronic Devices. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2022; 2022:5-8. [PMID: 36086039 DOI: 10.1109/embc48229.2022.9870827] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
The application of transparent conductive films to flexible biomedical optoelectronics is limited by stringent requirements on the candidate materials' electromechanical and optical properties as well as their biological performance. Thin films of graphene and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) are sought as mechanically flexible alternatives to traditional indium tin oxide (ITO). However, they require more understanding of their suitability for biomedical optoelectronic devices in terms of transmission behavior and electromechanical stability. This study shows that the relative increase in sheet resistance under cyclic loading for ITO, graphene, and PEDOT:PSS was 3546±3908%,12±2.7%, and 62±68%, respectively. Moreover, graphene and PEDOT:PSS showed a transmission uniformity of 9.3% and 36.3% (380-2000 nm), respectively, compared with ITO film (61%). Understanding the optical, electrical, and mechanical limits of the transparent conductive films facilitates the optimization of flexible optoelectronic designs to fit multiple biomedical research and clinical applications.
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Murphy BB, Apollo NV, Unegbu P, Posey T, Rodriguez-Perez N, Hendricks Q, Cimino F, Richardson AG, Vitale F. Vitamin C-reduced graphene oxide improves the performance and stability of multimodal neural microelectrodes. iScience 2022; 25:104652. [PMID: 35811842 PMCID: PMC9263525 DOI: 10.1016/j.isci.2022.104652] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2022] [Revised: 05/28/2022] [Accepted: 06/16/2022] [Indexed: 11/28/2022] Open
Abstract
Nanocarbons are often employed as coatings for neural electrodes to enhance surface area. However, processing and integrating them into microfabrication flows requires complex and harmful chemical and heating conditions. This article presents a safe, scalable, cost-effective method to produce reduced graphene oxide (rGO) coatings using vitamin C (VC) as the reducing agent. We spray coat GO + VC mixtures onto target substrates, and then heat samples for 15 min at 150°C. The resulting rGO films have conductivities of ∼44 S cm−1, and are easily integrated into an ad hoc microfabrication flow. The rGO/Au microelectrodes show ∼8x lower impedance and ∼400x higher capacitance than bare Au, resulting in significantly enhanced charge storage and injection capacity. We subsequently use rGO/Au arrays to detect dopamine in vitro, and to map cortical activity intraoperatively over rat whisker barrel cortex, demonstrating that conductive VC-rGO coatings improve the performance and stability of multimodal microelectrodes for different applications. Easy, scalable, and safe reduction method to create rGO films with vitamin C VC-rGO coatings improve the performance of bare gold microelectrodes in vitro VC-rGO coatings enable the voltammetric detection of dopamine on the microscale rGO/Au electrode arrays enable high-resolution microscale recording in vivo
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Affiliation(s)
- Brendan B. Murphy
- Department of Bioengineering, University of Pennsylvania, Philadelphia, PA 19104, USA
- Center for Neuroengineering and Therapeutics, University of Pennsylvania, Philadelphia, PA 19104, USA
- Center for Neurotrauma, Neurodegeneration and Restoration, Corporal Michael J. Crescenz Veterans Affairs Medical Center, Philadelphia, PA 19104, USA
| | - Nicholas V. Apollo
- Department of Bioengineering, University of Pennsylvania, Philadelphia, PA 19104, USA
- Center for Neuroengineering and Therapeutics, University of Pennsylvania, Philadelphia, PA 19104, USA
- Center for Neurotrauma, Neurodegeneration and Restoration, Corporal Michael J. Crescenz Veterans Affairs Medical Center, Philadelphia, PA 19104, USA
| | - Placid Unegbu
- Department of Bioengineering, University of Pennsylvania, Philadelphia, PA 19104, USA
- Center for Neuroengineering and Therapeutics, University of Pennsylvania, Philadelphia, PA 19104, USA
- Center for Neurotrauma, Neurodegeneration and Restoration, Corporal Michael J. Crescenz Veterans Affairs Medical Center, Philadelphia, PA 19104, USA
| | - Tessa Posey
- Department of Biomedical Engineering, University of South Carolina, Columbia, SC 29206, USA
| | - Nancy Rodriguez-Perez
- School of Sustainable Engineering and the Built Environment, Arizona State University, Tempe, AZ 85281, USA
| | - Quincy Hendricks
- Department of Bioengineering, University of Pennsylvania, Philadelphia, PA 19104, USA
- Center for Neuroengineering and Therapeutics, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Francesca Cimino
- Department of Bioengineering, University of Pennsylvania, Philadelphia, PA 19104, USA
- Center for Neuroengineering and Therapeutics, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Andrew G. Richardson
- Center for Neuroengineering and Therapeutics, University of Pennsylvania, Philadelphia, PA 19104, USA
- Department of Neurosurgery, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Flavia Vitale
- Department of Bioengineering, University of Pennsylvania, Philadelphia, PA 19104, USA
- Center for Neuroengineering and Therapeutics, University of Pennsylvania, Philadelphia, PA 19104, USA
- Center for Neurotrauma, Neurodegeneration and Restoration, Corporal Michael J. Crescenz Veterans Affairs Medical Center, Philadelphia, PA 19104, USA
- Department of Physical Medicine and Rehabilitation, University of Pennsylvania, Philadelphia, PA 19146, USA
- Corresponding author
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The influence of physicochemical properties on the processibility of conducting polymers: A bioelectronics perspective. Acta Biomater 2022; 139:259-279. [PMID: 34111518 DOI: 10.1016/j.actbio.2021.05.052] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Revised: 05/24/2021] [Accepted: 05/25/2021] [Indexed: 12/20/2022]
Abstract
Conducting polymers (CPs) possess unique electrical and electrochemical properties and hold great potential for different applications in the field of bioelectronics. However, the widespread implementation of CPs in this field has been critically hindered by their poor processibility. There are four key elements that determine the processibility of CPs, which are thermal tunability, chemical stability, solvent compatibility and mechanical robustness. Recent research efforts have focused on enhancing the processibility of these materials through pre- or post-synthesis chemical modifications, the fabrication of CP-based complexes and composites, and the adoption of additive manufacturing techniques. In this review, the physicochemical and structural properties that underlie the performance and processibility of CPs are examined. In addition, current research efforts to overcome technical limitations and broaden the potential applications of CPs in bioelectronics are discussed. STATEMENT OF SIGNIFICANCE: This review details the inherent properties of CPs that have hindered their use in additive manufacturing for the creation of 3D bioelectronics. A fundamental approach is presented with consideration of the chemical structure and how this contributes to their electrical, thermal and mechanical properties. The review then considers how manipulation of these properties has been addressed in the literature including areas where improvements can be made. Finally, the review details the use of CPs in additive manufacturing and the future scope for the use of CPs and their composites in the development of 3D bioelectronics.
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10
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della Valle E, Koo B, Patel PR, Whitsitt Q, Purcell EK, Chestek CA, Weiland JD. Electrodeposited Platinum Iridium Enables Microstimulation With Carbon Fiber Electrodes. FRONTIERS IN NANOTECHNOLOGY 2021. [DOI: 10.3389/fnano.2021.782883] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Ultrasmall microelectrode arrays have the potential to improve the spatial resolution of microstimulation. Carbon fiber (CF) microelectrodes with cross-sections of less than 8 μm have been demonstrated to penetrate cortical tissue and evoke minimal scarring in chronic implant tests. In this study, we investigate the stability and performance of neural stimulation electrodes comprised of electrodeposited platinum-iridium (PtIr) on carbon fibers. We conducted pulse testing and characterized charge injection in vitro and recorded voltage transients in vitro and in vivo. Standard electrochemical measurements (impedance spectroscopy and cyclic voltammetry) and visual inspection (scanning electron microscopy) were used to assess changes due to pulsing. Similar to other studies, the application of pulses caused a decrease in impedance and a reduction in voltage transients, but analysis of the impedance data suggests that these changes are due to surface modification and not permanent changes to the electrode. Comparison of scanning electron microscope images before and after pulse testing confirmed electrode stability.
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11
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Hyakumura T, Aregueta-Robles U, Duan W, Villalobos J, Adams WK, Poole-Warren L, Fallon JB. Improving Deep Brain Stimulation Electrode Performance in vivo Through Use of Conductive Hydrogel Coatings. Front Neurosci 2021; 15:761525. [PMID: 34803592 PMCID: PMC8602793 DOI: 10.3389/fnins.2021.761525] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2021] [Accepted: 10/11/2021] [Indexed: 11/13/2022] Open
Abstract
Active implantable neurological devices like deep brain stimulators have been used over the past few decades to treat movement disorders such as those in people with Parkinson’s disease and more recently, in psychiatric conditions like obsessive compulsive disorder. Electrode-tissue interfaces that support safe and effective targeting of specific brain regions are critical to success of these devices. Development of directional electrodes that activate smaller volumes of brain tissue requires electrodes to operate safely with higher charge densities. Coatings such as conductive hydrogels (CHs) provide lower impedances and higher charge injection limits (CILs) than standard platinum electrodes and support safer application of smaller electrode sizes. The aim of this study was to examine the chronic in vivo performance of a new low swelling CH coating that supports higher safe charge densities than traditional platinum electrodes. A range of hydrogel blends were engineered and their swelling and electrical performance compared. Electrochemical performance and stability of high and low swelling formulations were compared during insertion into a model brain in vitro and the formulation with lower swelling characteristics was chosen for the in vivo study. CH-coated or uncoated Pt electrode arrays were implanted into the brains of 14 rats, and their electrochemical performance was tested weekly for 8 weeks. Tissue response and neural survival was assessed histologically following electrode array removal. CH coating resulted in significantly lower voltage transient impedance, higher CIL, lower electrochemical impedance spectroscopy, and higher charge storage capacity compared to uncoated Pt electrodes in vivo, and this advantage was maintained over the 8-week implantation. There was no significant difference in evoked potential thresholds, signal-to-noise ratio, tissue response or neural survival between CH-coated and uncoated Pt groups. The significant electrochemical advantage and stability of CH coating in the brain supports the suitability of this coating technology for future development of smaller, higher fidelity electrode arrays with higher charge density requirement.
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Affiliation(s)
- Tomoko Hyakumura
- The Bionics Institute of Australia, East Melbourne, VIC, Australia.,Department of Medical Bionics, The University of Melbourne, Parkville, VIC, Australia
| | - Ulises Aregueta-Robles
- Graduate School of Biomedical Engineering, The University of New South Wales, Sydney, NSW, Australia
| | - Wenlu Duan
- Graduate School of Biomedical Engineering, The University of New South Wales, Sydney, NSW, Australia
| | - Joel Villalobos
- The Bionics Institute of Australia, East Melbourne, VIC, Australia.,Department of Medical Bionics, The University of Melbourne, Parkville, VIC, Australia
| | - Wendy K Adams
- The Bionics Institute of Australia, East Melbourne, VIC, Australia
| | - Laura Poole-Warren
- Graduate School of Biomedical Engineering, The University of New South Wales, Sydney, NSW, Australia.,Tyree Foundation Institute of Health Engineering, The University of New South Wales, Sydney, NSW, Australia
| | - James B Fallon
- The Bionics Institute of Australia, East Melbourne, VIC, Australia.,Department of Medical Bionics, The University of Melbourne, Parkville, VIC, Australia
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Dalrymple AN, Ting JE, Bose R, Trevathan JK, Nieuwoudt S, Lempka SF, Franke M, Ludwig KA, Shoffstall AJ, Fisher LE, Weber DJ. Stimulation of the dorsal root ganglion using an Injectrode ®. J Neural Eng 2021; 18. [PMID: 34650008 DOI: 10.1088/1741-2552/ac2ffb] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2021] [Accepted: 10/14/2021] [Indexed: 01/15/2023]
Abstract
Objective. The goal of this work was to compare afferent fiber recruitment by dorsal root ganglion (DRG) stimulation using an injectable polymer electrode (Injectrode®) and a more traditional cylindrical metal electrode.Approach. We exposed the L6 and L7 DRG in four cats via a partial laminectomy or burr hole. We stimulated the DRG using an Injectrode or a stainless steel (SS) electrode using biphasic pulses at three different pulse widths (80, 150, 300μs) and pulse amplitudes spanning the range used for clinical DRG stimulation. We recorded antidromic evoked compound action potentials (ECAPs) in the sciatic, tibial, and common peroneal nerves using nerve cuffs. We calculated the conduction velocity of the ECAPs and determined the charge-thresholds and recruitment rates for ECAPs from Aα, Aβ, and Aδfibers. We also performed electrochemical impedance spectroscopy measurements for both electrode types.Main results. The ECAP thresholds for the Injectrode did not differ from the SS electrode across all primary afferents (Aα, Aβ, Aδ) and pulse widths; charge-thresholds increased with wider pulse widths. Thresholds for generating ECAPs from Aβfibers were 100.0 ± 32.3 nC using the SS electrode, and 90.9 ± 42.9 nC using the Injectrode. The ECAP thresholds from the Injectrode were consistent over several hours of stimulation. The rate of recruitment was similar between the Injectrodes and SS electrode and decreased with wider pulse widths.Significance. The Injectrode can effectively excite primary afferents when used for DRG stimulation within the range of parameters used for clinical DRG stimulation. The Injectrode can be implanted through minimally invasive techniques while achieving similar neural activation to conventional electrodes, making it an excellent candidate for future DRG stimulation and neuroprosthetic applications.
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Affiliation(s)
- Ashley N Dalrymple
- Department of Mechanical Engineering, Carnegie Mellon University, 5000 Forbes Ave, Wean 1323, Pittsburgh, PA 15217, United States of America.,Rehab Neural Engineering Labs, University of Pittsburgh, Pittsburgh, PA, 15217, United States of America
| | - Jordyn E Ting
- Rehab Neural Engineering Labs, University of Pittsburgh, Pittsburgh, PA, 15217, United States of America.,Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, United States of America.,Center for Neural Basis of Cognition, Pittsburgh, PA, 15217, United States of America
| | - Rohit Bose
- Rehab Neural Engineering Labs, University of Pittsburgh, Pittsburgh, PA, 15217, United States of America.,Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, United States of America.,Center for Neural Basis of Cognition, Pittsburgh, PA, 15217, United States of America
| | - James K Trevathan
- Departments of Biomedical Engineering and Neurological Surgery, University of Wisconsin-Madison, Madison, WI, United States of America
| | | | - Scott F Lempka
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, United States of America
| | | | - Kip A Ludwig
- Departments of Biomedical Engineering and Neurological Surgery, University of Wisconsin-Madison, Madison, WI, United States of America.,Neuronoff Inc., Cleveland, OH, United States of America.,Wisconsin Institute for Translational Neuroengineering (WITNe), Madison, WI, United States of America
| | - Andrew J Shoffstall
- Neuronoff Inc., Cleveland, OH, United States of America.,Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, United States of America
| | - Lee E Fisher
- Rehab Neural Engineering Labs, University of Pittsburgh, Pittsburgh, PA, 15217, United States of America.,Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, United States of America.,Center for Neural Basis of Cognition, Pittsburgh, PA, 15217, United States of America.,Department of Physical Medicine and Rehabilitation, University of Pittsburgh, Pittsburgh, PA, United States of America
| | - Douglas J Weber
- Department of Mechanical Engineering, Carnegie Mellon University, 5000 Forbes Ave, Wean 1323, Pittsburgh, PA 15217, United States of America.,Rehab Neural Engineering Labs, University of Pittsburgh, Pittsburgh, PA, 15217, United States of America.,Center for Neural Basis of Cognition, Pittsburgh, PA, 15217, United States of America.,Neuroscience Institute, Carnegie Mellon University, 5000 Forbes Ave, Wean 1323, Pittsburgh, PA 15217, United States of America
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Shepherd RK, Carter PM, Dalrymple AN, Enke YL, Wise AK, Nguyen T, Firth J, Thompson A, Fallon JB. Platinum dissolution and tissue response following long-term electrical stimulation at high charge densities. J Neural Eng 2021; 18:10.1088/1741-2552/abe5ba. [PMID: 33578409 PMCID: PMC8711780 DOI: 10.1088/1741-2552/abe5ba] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Accepted: 02/12/2021] [Indexed: 11/11/2022]
Abstract
Objective. Established guidelines for safe levels of electrical stimulation for neural prostheses are based on a limited range of the stimulus parameters used clinically. Recent studies have reported particulate platinum (Pt) associated with long-term clinical use of these devices, highlighting the need for more carefully defined safety limits. We previously reported no adverse effects of Pt corrosion products in the cochleae of guinea pigs following 4 weeks of electrical stimulation using charge densities far greater than the published safe limits for cochlear implants. The present study examines the histopathological effects of Pt within the cochlea following continuous stimulation at a charge density well above the defined safe limits for periods up to 6 months.Approach. Six cats were bilaterally implanted with Pt electrode arrays and unilaterally stimulated using charge balanced current pulses at a charge density of 267μC cm-2phase-1using a tripolar electrode configuration. Electrochemical measurements were made throughout the implant duration and evoked potentials recorded at the outset and on completion of the stimulation program. Cochleae were examined histologically for particulate Pt, tissue response, and auditory nerve survival; electrodes were examined for surface corrosion; and cochlea, brain, kidney, and liver tissue analysed for trace levels of Pt.Main results. Chronic stimulation resulted in both a significant increase in tissue response and particulate Pt within the tissue capsule surrounding the electrode array compared with implanted, unstimulated control cochleae. Importantly, there was no stimulus-induced loss of auditory neurons (ANs) or increase in evoked potential thresholds. Stimulated electrodes were significantly more corroded compared with unstimulated electrodes. Trace analysis revealed Pt in both stimulated and control cochleae although significantly greater levels were detected within stimulated cochleae. There was no evidence of Pt in brain or liver; however, trace levels of Pt were recorded in the kidneys of two animals. Finally, increased charge storage capacity and charge injection limit reflected the more extensive electrode corrosion associated with stimulated electrodes.Significance. Long-term electrical stimulation of Pt electrodes at a charge density well above existing safety limits and nearly an order of magnitude higher than levels used clinically, does not adversely affect the AN population or reduce neural function, despite a stimulus-induced tissue response and the accumulation of Pt corrosion product. The mechanism resulting in Pt within the unstimulated cochlea is unclear, while the level of Pt observed systemically following stimulation at these very high charge densities does not appear to be of clinical significance.
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Affiliation(s)
- Robert K Shepherd
- Bionics Institute, St Vincent's Hospital, Melbourne, Australia
- Medical Bionics Department, University of Melbourne, Melbourne, Australia
| | | | - Ashley N Dalrymple
- Bionics Institute, St Vincent's Hospital, Melbourne, Australia
- Department of Mechanical Engineering, Carnegie Mellon University, Pittsburgh, PA, United States of America
| | | | - Andrew K Wise
- Bionics Institute, St Vincent's Hospital, Melbourne, Australia
- Medical Bionics Department, University of Melbourne, Melbourne, Australia
| | - Trung Nguyen
- Bionics Institute, St Vincent's Hospital, Melbourne, Australia
| | - James Firth
- Bionics Institute, St Vincent's Hospital, Melbourne, Australia
| | - Alex Thompson
- Bionics Institute, St Vincent's Hospital, Melbourne, Australia
| | - James B Fallon
- Bionics Institute, St Vincent's Hospital, Melbourne, Australia
- Medical Bionics Department, University of Melbourne, Melbourne, Australia
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Elyahoodayan S, Jiang W, Lee CD, Shao X, Weiland G, Whalen JJ, Petrossians A, Song D. Stimulation and Recording of the Hippocampus Using the Same Pt-Ir Coated Microelectrodes. Front Neurosci 2021; 15:616063. [PMID: 33716647 PMCID: PMC7943859 DOI: 10.3389/fnins.2021.616063] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2020] [Accepted: 01/28/2021] [Indexed: 01/11/2023] Open
Abstract
Same-electrode stimulation and recording with high spatial resolution, signal quality, and power efficiency is highly desirable in neuroscience and neural engineering. High spatial resolution and signal-to-noise ratio is necessary for obtaining unitary activities and delivering focal stimulations. Power efficiency is critical for battery-operated implantable neural interfaces. This study demonstrates the capability of recording single units as well as evoked potentials in response to a wide range of electrochemically safe stimulation pulses through high-resolution microelectrodes coated with co-deposition of Pt-Ir. It also compares signal-to-noise ratio, single unit activity, and power efficiencies between Pt-Ir coated and uncoated microelectrodes. To enable stimulation and recording with the same microelectrodes, microelectrode arrays were treated with electrodeposited platinum-iridium coating (EPIC) and tested in the CA1 cell body layer of rat hippocampi. The electrodes' ability to (1) inject a large range of electrochemically reversable stimulation pulses to the tissue, and (2) record evoked potentials and single unit activities were quantitively assessed over an acute time period. Compared to uncoated electrodes, EPIC electrodes recorded signals with higher signal-to-noise ratios (coated: 9.77 ± 1.95 dB; uncoated: 1.95 ± 0.40 dB) and generated lower voltages (coated: 100 mV; uncoated: 650 mV) for a given stimulus (5 μA). The improved performance corresponded to lower energy consumptions and electrochemically safe stimulation above 5 μA (>0.38 mC/cm2), which enabled elicitation of field excitatory post synaptic potentials and population spikes. Spontaneous single unit activities were also modulated by varying stimulation intensities and monitored through the same electrodes. This work represents an example of stimulation and recording single unit activities from the same microelectrode, which provides a powerful tool for monitoring and manipulating neural circuits at the single neuron level.
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Affiliation(s)
- Sahar Elyahoodayan
- Department of Biomedical Engineering, Center for Neural Engineering, University of Southern California, Los Angeles, CA, United States
| | - Wenxuan Jiang
- Department of Biomedical Engineering, Center for Neural Engineering, University of Southern California, Los Angeles, CA, United States
| | | | - Xiecheng Shao
- Department of Biomedical Engineering, Center for Neural Engineering, University of Southern California, Los Angeles, CA, United States
| | | | | | | | - Dong Song
- Department of Biomedical Engineering, Center for Neural Engineering, University of Southern California, Los Angeles, CA, United States
- Neuroscience Graduate Program, University of Southern California, Los Angeles, CA, United States
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Dalrymple AN. Implanted devices: the importance of both electrochemical performance and biological acceptance. Neural Regen Res 2021; 16:1188-1189. [PMID: 33269769 PMCID: PMC8224142 DOI: 10.4103/1673-5374.300342] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Affiliation(s)
- Ashley N Dalrymple
- Department of Physical Medicine and Rehabilitation Rehabilitation Neural Engineering Labs, University of Pittsburgh, Pittsburgh, PA, USA
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Shepherd RK, Carter PM, Enke YL, Thompson A, Flynn B, Trang EP, Dalrymple AN, Fallon JB. Chronic intracochlear electrical stimulation at high charge densities: reducing platinum dissolution. J Neural Eng 2020; 17:056009. [DOI: 10.1088/1741-2552/abb7a6] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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Dalrymple AN, Huynh M, Nayagam BA, Lee CD, Weiland GR, Petrossians A, J J, Iii W, Fallon JB, Shepherd RK. Electrochemical and biological characterization of thin-film platinum-iridium alloy electrode coatings: a chronic in vivo study. J Neural Eng 2020; 17:036012. [PMID: 32408281 DOI: 10.1088/1741-2552/ab933d] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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 h d, 5 d week-1 for 5 weeks at levels within the normal clinical range. 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.
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Dalrymple AN, Robles UA, Huynh M, Nayagam BA, Green RA, Poole-Warren LA, Fallon JB, Shepherd RK. Electrochemical and biological performance of chronically stimulated conductive hydrogel electrodes. J Neural Eng 2020; 17:026018. [DOI: 10.1088/1741-2552/ab7cfc] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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