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Harris AR, Grayden DB, John SE. Electrochemistry in a Two- or Three-Electrode Configuration to Understand Monopolar or Bipolar Configurations of Platinum Bionic Implants. MICROMACHINES 2023; 14:722. [PMID: 37420955 DOI: 10.3390/mi14040722] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2023] [Revised: 03/21/2023] [Accepted: 03/22/2023] [Indexed: 07/09/2023]
Abstract
Electrodes are used in vivo for chemical sensing, electrophysiological recording, and stimulation of tissue. The electrode configuration used in vivo is often optimised for a specific anatomy and biological or clinical outcomes, not electrochemical performance. Electrode materials and geometries are constrained by biostability and biocompatibility issues and may be required to function clinically for decades. We performed benchtop electrochemistry, with changes in reference electrode, smaller counter-electrode sizes, and three- or two-electrode configurations. We detail the effects different electrode configurations have on typical electroanalytical techniques used on implanted electrodes. Changes in reference electrode required correction by application of an offset potential. In a two-electrode configuration with similar working and reference/counter-electrode sizes, the electrochemical response was dictated by the rate-limiting charge transfer step at either electrode. This could invalidate calibration curves, standard analytical methods, and equations, and prevent use of commercial simulation software. We provide methods for determining if an electrode configuration is affecting the in vivo electrochemical response. We recommend sufficient details be provided in experimental sections on electronics, electrode configuration, and their calibration to justify results and discussion. In conclusion, the experimental limitations of performing in vivo electrochemistry may dictate what types of measurements and analyses are possible, such as obtaining relative rather than absolute measurements.
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Affiliation(s)
- Alexander R Harris
- Department of Biomedical Engineering, University of Melbourne, Melbourne 3010, Australia
| | - David B Grayden
- Department of Biomedical Engineering, University of Melbourne, Melbourne 3010, Australia
- Graeme Clark Institute, University of Melbourne, Melbourne 3010, Australia
| | - Sam E John
- Department of Biomedical Engineering, University of Melbourne, Melbourne 3010, Australia
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Ong S, Kullmann A, Mertens S, Rosa D, Diaz-Botia CA. Electrochemical Testing of a New Polyimide Thin Film Electrode for Stimulation, Recording, and Monitoring of Brain Activity. MICROMACHINES 2022; 13:1798. [PMID: 36296151 PMCID: PMC9611492 DOI: 10.3390/mi13101798] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/20/2022] [Revised: 10/13/2022] [Accepted: 10/15/2022] [Indexed: 06/16/2023]
Abstract
Subdural electrode arrays are used for monitoring cortical activity and functional brain mapping in patients with seizures. Until recently, the only commercially available arrays were silicone-based, whose thickness and lack of conformability could impact their performance. We designed, characterized, manufactured, and obtained FDA clearance for 29-day clinical use (510(k) K192764) of a new thin-film polyimide-based electrode array. This study describes the electrochemical characterization undertaken to evaluate the quality and reliability of electrical signal recordings and stimulation of these new arrays. Two testing paradigms were performed: a short-term active soak with electrical stimulation and a 29-day passive soak. Before and after each testing paradigm, the arrays were evaluated for their electrical performance using Electrochemical Impedance Spectroscopy (EIS), Cyclic Voltammetry (CV) and Voltage Transients (VT). In all tests, the impedance remained within an acceptable range across all frequencies. The different CV curves showed no significant changes in shape or area, which is indicative of stable electrode material. The electrode polarization remained within appropriate limits to avoid hydrolysis.
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Comparison of the In Vitro and In Vivo Electrochemical Performance of Bionic Electrodes. MICROMACHINES 2022; 13:mi13010103. [PMID: 35056268 PMCID: PMC8779563 DOI: 10.3390/mi13010103] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/30/2021] [Revised: 12/14/2021] [Accepted: 01/04/2022] [Indexed: 12/13/2022]
Abstract
The electrochemical performance of platinum electrodes was assessed in vitro and in vivo to determine the impact of electrode implantation and the relevance of in vitro testing in predicting in vivo behaviour. A significant change in electrochemical response was seen after electrode polarisation. As a result, initial in vitro measurements were poor predictors of subsequent measurements performed in vitro or in vivo. Charge storage capacity and charge density measurements from initial voltammetric measurements were not correlated with subsequent measurements. Electrode implantation also affected the electrochemical impedance. The typically reported impedance at 1 kHz was a very poor predictor of electrode performance. Lower frequencies were significantly more dependent on electrode properties, while higher frequencies were dependent on solution properties. Stronger correlations in impedance at low frequencies were seen between in vitro and in vivo measurements after electrode activation had occurred. Implanting the electrode increased the resistance of the electrochemical circuit, with bone having a higher resistivity than soft tissue. In contrast, protein fouling and fibrous tissue formation had a minimal impact on electrochemical response. In vivo electrochemical measurements also typically use a quasi-reference electrode, may operate in a 2-electrode system, and suffer from uncompensated resistance. The impact of these experimental conditions on electrochemical performance and the relevance of in vitro electrode assessment is discussed. Recommended in vitro testing protocols for assessing bionic electrodes are presented.
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Wang C, Rubakhin SS, Enright MJ, Sweedler JV, Nuzzo RG. 3D Particle Free Printing of Biocompatible Conductive Hydrogel Platforms for Neuron Growth and Electrophysiological Recording. ADVANCED FUNCTIONAL MATERIALS 2021; 31:2010246. [PMID: 34305503 PMCID: PMC8297588 DOI: 10.1002/adfm.202010246] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2020] [Indexed: 05/26/2023]
Abstract
Electrically conductive 3D periodic microscaffolds are fabricated using a particle-free direct ink writing approach for use as neuronal growth and electrophysiological recording platforms. A poly (2-hydroxyethyl methacrylate) (pHEMA)/pyrrole ink, followed by chemical in situ polymerization of pyrrole, enables hydrogel printing through nozzles as small as 1 μm. These conductive hydrogels can pattern complex 2D and 3D structures and have good biocompatibility with test cell cultures (~94.5% viability after 7 days). Hydrogel arrays promote extensive neurite outgrowth of cultured Aplysia californica pedal ganglion neurons. This platform allows extracellular electrophysiological recording of steady-state and stimulated electrical neuronal activities. In summation, this 3D conductive ink printing process enables preparation of biocompatible and micron-sized structures to create customized in vitro electrophysiological recording platforms.
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Affiliation(s)
- Chen Wang
- Frederick Seitz Materials Research Laboratory and Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, 1304 West Green Street, Urbana, IL 61801, USA
| | | | - Michael J Enright
- Department of Chemistry, University of Illinois at Urbana Champaign, 600 South Mathews Avenue, Urbana, IL 61801
| | - Jonathan V Sweedler
- Department of Chemistry, University of Illinois, 71 RAL, Box 63-5, 600 South Mathews Avenue, Urbana, IL 61801
| | - Ralph G Nuzzo
- Department of Chemistry, University of Illinois at Urbana Champaign, 600 South Mathews Avenue, Urbana, IL 61801
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Fibrinogen, collagen, and transferrin adsorption to poly(3,4-ethylenedioxythiophene)-xylorhamno-uronic glycan composite conducting polymer biomaterials for wound healing applications. Biointerphases 2021; 16:021003. [PMID: 33752337 DOI: 10.1116/6.0000708] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
We present the conducting polymer poly (3,4-ethylenedioxythiophene) (PEDOT) doped with an algal-derived glycan extract, Phycotrix™ [xylorhamno-uronic glycan (XRU84)], as an innovative electrically conductive material capable of providing beneficial biological and electrical cues for the promotion of favorable wound healing processes. Increased loading of the algal XRU84 into PEDOT resulted in a reduced surface nanoroughness and interfacial surface area and an increased static water contact angle. PEDOT-XRU84 films demonstrated good electrical stability and charge storage capacity and a reduced impedance relative to the control gold electrode. A quartz crystal microbalance with dissipation monitoring study of protein adsorption (transferrin, fibrinogen, and collagen) showed that collagen adsorption increased significantly with increased XRU84 loading, while transferrin adsorption was significantly reduced. The viscoelastic properties of adsorbed protein, characterized using the ΔD/Δf ratio, showed that for transferrin and fibrinogen, a rigid, dehydrated layer was formed at low XRU84 loadings. Cell studies using human dermal fibroblasts demonstrated excellent cell viability, with fluorescent staining of the cell cytoskeleton illustrating all polymers to present excellent cell adhesion and spreading after 24 h.
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Harris AR, Carter P, Cowan R, Wallace GG. Impact of Protein Fouling on the Charge Injection Capacity, Impedance, and Effective Electrode Area of Platinum Electrodes for Bionic Devices. ChemElectroChem 2021. [DOI: 10.1002/celc.202001574] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Affiliation(s)
- Alexander R. Harris
- Aikenhead Centre for Medical Discovery ARC Centre of Excellence for Electromaterials Science Faculty of Medicine, Dentistry and Health Sciences University of Melbourne Melbourne Vic 3010 Australia
- The HEARing CRC University of Melbourne 550 Swanston St Melbourne 3010 Australia
| | - Paul Carter
- Cochlear Ltd Macquarie University 1 University Ave Sydney NSW 2109 Australia
| | - Robert Cowan
- The HEARing CRC University of Melbourne 550 Swanston St Melbourne 3010 Australia
- Department of Audiology & Speech Pathology University of Melbourne 550 Swanston St Melbourne 3010 Australia
| | - Gordon G. Wallace
- ARC Centre of Excellence for Electromaterials Science Intelligent Polymer Research Institute University of Wollongong Wollongong, NSW 2522 Australia
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Harris A. Understanding Charge Transfer on the Clinically Used Conical Utah Electrode Array: Charge Storage Capacity, Electrochemical Impedance Spectroscopy and Effective Electrode Area. J Neural Eng 2021; 18. [PMID: 33401255 DOI: 10.1088/1741-2552/abd897] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2020] [Accepted: 01/05/2021] [Indexed: 11/11/2022]
Abstract
OBJECTIVE The Utah electrode is used for pre/clinical studies on neural recording and stimulation. Anecdotal and empirical reports on their performance have been made, resulting in variable testing methods. An in depth investigation was performed to understand the electrochemical behaviour and charge transfer mechanisms occurring on these clinically important electrodes. APPROACH Platinum and iridium electrodes were assessed by cyclic voltammetry and electrochemical impedance spectroscopy. The effective electrode area was measured by reduction of Ru(NH3)63+. MAIN RESULTS Pristine Utah electrodes have little to no oxide present and the surface roughness is very low. Pristine iridium electrodes pass charge through capacitance and oxide formation. Hydride and anion adsorption occurs on the platinum electrode. Anodic current oxidises both metal surfaces, altering the charge transfer mechanisms at the electrode-solution interface. The charge storage capacity depends on measurement technique and electrode structure, providing no information on charge transfer mechanisms. Electrode oxidation increases pseudocapacitance, reducing impedance. Charge transfer was non-homogeneous, most likely due to the electrode geometry enhancing charge density at the electrode tip and base. Oxidation of the electrode surface enhanced charge transfer inhomogeneity. The effective electrode area could be measured by reduction of Ru(NH3)63+ and calculated with a finite cone geometry. SIGNIFICANCE Increasing electrode pseudocapacitance, demonstrated by metal oxidation, reduces impedance. Increasing electrode capacitance offers a potential route to reducing thermal noise and increasing signal-to-noise ratio of neural recording. The effective electrode area of conical electrodes can be measured. The charge density of the conical electrode was greater than expected on a planar disc electrode, indicating modification of electrode geometry can increase an electrodes safe charge injection capacity. In vivo electrochemical measurements often don't include sufficient details to understand the electrode behaviour. Electrode oxidation most likely accounts for a significant amount of variation in previously published Utah electrode impedance data.
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Affiliation(s)
- Alex Harris
- Faculty of Medicine, Dentistry and Health Sciences, University of Melbourne, Aikenhead Centre for Medical Discovery, Melbourne, Victoria, 3065, AUSTRALIA
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Gnatkovsky V, Cattalini A, Antonini A, Spreafico L, Saini M, Noè F, Alessi C, Librizzi L, Uva L, Marras CE, de Curtis M, Ferrari S. Recording Electrical Brain Activity with Novel Stretchable Electrodes Based on Supersonic Cluster Beam Implantation Nanotechnology on Conformable Polymers. Int J Nanomedicine 2020; 14:10079-10089. [PMID: 31920304 PMCID: PMC6935312 DOI: 10.2147/ijn.s224243] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2019] [Accepted: 09/25/2019] [Indexed: 11/23/2022] Open
Abstract
Background Multielectrodes are implanted in central and peripheral nervous systems for rehabilitation and diagnostic purposes. The physical resistance of intracranial devices to mechanical stress is critical and fractures or electrode displacement may occur. We describe here a new recording device with stretchable properties based on Supersonic Cluster Beam Implantation (SCBI) technology with high mechanical adaptability to displacement and movement. Results The capability of SCBI-based multichannel electrodes to record brain electrical activity was compared to glass/silicon microelectrodes in acute in vitro experiments on the isolated guinea pig brain preparation. Field potentials and power frequency analysis demonstrated equal recording features for SCBI and standard electrodes. Chronic in vivo epidural implantation of the SCBI electrodes confirmed excellent long-term recording properties in comparison to standard EEG metal electrodes. Tissue biocompatibility was demonstrated by neuropathological evaluation of the brain tissue 2 months after the implantation of the devices in the subarachnoid space. Conclusion We confirm the biocompatibility of novel SCBI-based stretchable electrode devices and demonstrate their suitability for recording electrical brain activity in pre-clinical settings.
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Affiliation(s)
- Vadym Gnatkovsky
- Unit of Epileptology, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milano, Italy
| | - Alessandro Cattalini
- Unit of Epileptology, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milano, Italy
| | | | | | | | - Francesco Noè
- Unit of Epileptology, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milano, Italy
| | - Camilla Alessi
- Unit of Epileptology, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milano, Italy
| | - Laura Librizzi
- Unit of Epileptology, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milano, Italy
| | - Laura Uva
- Unit of Epileptology, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milano, Italy
| | - Carlo Efisio Marras
- Neurosurgery Unit, Department of Neuroscience and Neurorehabilitation, IRCCS Bambino Gesù Children's Hospital, Roma, Italy
| | - Marco de Curtis
- Unit of Epileptology, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milano, Italy
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