1
|
Berger E, Brandes G, Kaiser O, Reifenrath J, Lenarz T, Wissel K, Durisin M. Induction of cell death by sodium hexachloroplatinate (IV) in the HEI-OC1 cell line, primary rat spiral ganglion cells and rat organ of Corti explants. PLoS One 2024; 19:e0307973. [PMID: 39058727 PMCID: PMC11280268 DOI: 10.1371/journal.pone.0307973] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2024] [Accepted: 07/15/2024] [Indexed: 07/28/2024] Open
Abstract
Although cochlear implants have become a well-established method for patients with sensory neural hearing loss, clinical results indicate that in some cases, corrosion of electrode contacts leads to high impedance that interferes with successful stimulation of the auditory nerve. As it is unclear whether corrosion products induce cell damage, we focused on cell culture models of the organ of Corti cell line (HEI-OC1), rat spiral ganglion cells (SGC) and rat organ of Corti explant (OCex) cultivated from neonatal rat cochleae to characterize the cytotoxicity of sodium hexachloroplatinate (IV) (Na2(PtCl6)). The oxidative activity in HEI-OC1 cells decreased with increasing Na2(PtCl6) concentrations between 8 and 16 ng/μl, and live cell staining with Calcein acetoxymethyl/Ethidium homodimer III revealed an increasing number of cells with disrupted membranes. Ultrastructural evidence of mitophagy followed by necroptosis was detected. Additionally, exposure of the SGC to 15-35 ng/μl Na2(PtCl6) dose-dependently reduced neuronal survival and neuritogenesis, as determined by neurofilament antigen staining. In parallel, staining glial cells and fibroblasts with specific antibodies confirmed the dose-dependent induction of cell death by Na2(PtCl6). Exposure of the OCex to 25-45 ng/μl Na2(PtCl6) resulted in severe concentration-dependent hair cell loss. Our data show for the first time that Na2(PtCl6) induces cell death in a concentration-dependent manner in inner ear cell types and tissues.
Collapse
Affiliation(s)
- Elisabeth Berger
- Department of Otorhinolaryngology, Hannover Medical School, Hannover, Germany
- Lower Saxony Centre for Biomedical Engineering, Implant Research and Development (NIFE), Hannover Medical School, Hannover, Germany
| | - Gudrun Brandes
- Hannover Medical School, Institute of Neuroanatomy and Cell Biology, Hannover, Germany
| | - Odett Kaiser
- Department of Otorhinolaryngology, Hannover Medical School, Hannover, Germany
- Lower Saxony Centre for Biomedical Engineering, Implant Research and Development (NIFE), Hannover Medical School, Hannover, Germany
| | - Janin Reifenrath
- Lower Saxony Centre for Biomedical Engineering, Implant Research and Development (NIFE), Hannover Medical School, Hannover, Germany
- Clinic for Orthopaedic Surgery, Hannover Medical School, Hannover, Germany
| | - Thomas Lenarz
- Department of Otorhinolaryngology, Hannover Medical School, Hannover, Germany
- Lower Saxony Centre for Biomedical Engineering, Implant Research and Development (NIFE), Hannover Medical School, Hannover, Germany
| | - Kirsten Wissel
- Department of Otorhinolaryngology, Hannover Medical School, Hannover, Germany
- Lower Saxony Centre for Biomedical Engineering, Implant Research and Development (NIFE), Hannover Medical School, Hannover, Germany
| | - Martin Durisin
- Department of Otorhinolaryngology, Hannover Medical School, Hannover, Germany
- Lower Saxony Centre for Biomedical Engineering, Implant Research and Development (NIFE), Hannover Medical School, Hannover, Germany
- University Clinic of Otolaryngology, Head and Neck Surgery, Otto-von-Guericke-University Magdeburg, Magdeburg, Germany
| |
Collapse
|
2
|
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.
Collapse
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
| | | |
Collapse
|
3
|
Salman IM. Key challenges in exploring the rat as a preclinical neurostimulation model for aortic baroreflex modulation in hypertension. Hypertens Res 2024; 47:399-415. [PMID: 37919429 DOI: 10.1038/s41440-023-01486-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2023] [Revised: 10/02/2023] [Accepted: 10/06/2023] [Indexed: 11/04/2023]
Abstract
Electrode-based electrophysiological interfaces with peripheral nerves have come a long way since the 1960s, with several neurostimulation applications witnessing widespread clinical implementation since then. In resistant hypertension, previous clinical trials have shown that "carotid" baroreflex stimulation using device-based baroreflex activation therapy (BAT) can effectively lower blood pressure (BP). However, device-based "aortic" baroreflex stimulation remains untouched for clinical translation. The rat is a remarkable animal model that facilitates exploration of mechanisms pertaining to the baroreceptor reflex and preclinical development of novel therapeutic strategies for BP modulation and hypertension treatment. Specifically, the aortic depressor nerve (ADN) in rats carries a relatively pure population of barosensitive afferent neurons, which enable selective investigation of the aortic baroreflex function. In a rat model of essential hypertension, the spontaneously hypertensive rat (SHR), we have recently investigated the aortic baroreceptor afferents as an alternate target for BP modulation, and showed that "low intensity" stimulation is able to evoke clinically meaningful reductions in BP. Deriving high quality short-term and long-term data on aortic baroreflex modulation in rats is currently hampered by a number of unresolved experimental challenges, including anatomical variations across rats which complicates identification of the ADN, the use of unrefined neurostimulation tools or paradigms, and issues arising from anesthetized and conscious surgical preparations. With the goal of refining existing experimental protocols designed for preclinical investigation of the baroreflex, this review seeks to outline current challenges hindering further progress in aortic baroreflex modulation studies in rats and present some practical considerations and recently emerging ideas to overcome them. Aortic baroreflex modulation.
Collapse
Affiliation(s)
- Ibrahim M Salman
- Department of Pharmaceutical Sciences, College of Pharmacy, Alfaisal University, Riyadh, Saudi Arabia.
| |
Collapse
|
4
|
Li L, Jiang C, Duan W, Wang Z, Zhang F, He C, Long T, Li L. Electrochemical and biological performance of hierarchical platinum-iridium electrodes structured by a femtosecond laser. MICROSYSTEMS & NANOENGINEERING 2022; 8:96. [PMID: 36065436 PMCID: PMC9440118 DOI: 10.1038/s41378-022-00433-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/23/2022] [Revised: 06/20/2022] [Accepted: 07/19/2022] [Indexed: 06/15/2023]
Abstract
Neural electrode interfaces are essential to the stimulation safety and recording quality of various bioelectronic therapies. The recently proposed hierarchical platinum-iridium (Pt-Ir) electrodes produced by femtosecond lasers have exhibited superior electrochemical performance in vitro, but their in vivo performance is still unclear. In this study, we explored the electrochemical performance, biological response, and tissue adhesion of hierarchical Pt-Ir electrodes by implantation in adult rat brains for 1, 8, and 16 weeks. Regular smooth Pt-Ir electrodes were used as a control. The results showed that the electrochemical performance of both electrodes decreased and leveled off during implantation. However, after 16 weeks, the charge storage capacity of hierarchical electrodes stabilized at ~16.8 mC/cm2, which was 15 times that of the smooth control electrodes (1.1 mC/cm2). Moreover, the highly structured electrodes had lower impedance amplitude and cutoff frequency values. The similar histological response to smooth electrodes indicated good biocompatibility of the hierarchically structured Pt-Ir electrodes. Given their superior in vivo performance, the femtosecond laser-treated Pt-Ir electrode showed great potential for neuromodulation applications.
Collapse
Affiliation(s)
- Linze Li
- National Engineering Research Center of Neuromodulation, School of Aerospace Engineering, Tsinghua University, Beijing, 100084 China
- School of Mechanical Engineering and Automation, Fuzhou University, Fuzhou, 350108 China
| | - Changqing Jiang
- National Engineering Research Center of Neuromodulation, School of Aerospace Engineering, Tsinghua University, Beijing, 100084 China
| | - Wanru Duan
- Department of Neurosurgery, China International Neuroscience Institute (CHINA-INI), Xuanwu Hospital, Capital Medical University, Beijing, 100053 China
- Lab of Spinal Cord Injury and Functional Reconstruction, China International Neuroscience Institute (CHINA-INI), Xuanwu Hospital, Capital Medical University, Beijing, 100053 China
| | - Zhiyan Wang
- National Engineering Research Center of Neuromodulation, School of Aerospace Engineering, Tsinghua University, Beijing, 100084 China
| | - Feng Zhang
- National Engineering Research Center of Neuromodulation, School of Aerospace Engineering, Tsinghua University, Beijing, 100084 China
| | - Changgeng He
- National Engineering Research Center of Neuromodulation, School of Aerospace Engineering, Tsinghua University, Beijing, 100084 China
| | - Tiangang Long
- National Engineering Research Center of Neuromodulation, School of Aerospace Engineering, Tsinghua University, Beijing, 100084 China
| | - Luming Li
- National Engineering Research Center of Neuromodulation, School of Aerospace Engineering, Tsinghua University, Beijing, 100084 China
- Precision Medicine & Healthcare Research Center, Tsinghua-Berkeley Shenzhen Institute, Tsinghua University, Shenzhen, 518071 China
- IDG/McGovern Institute for Brain Research at Tsinghua University, Beijing, 100084 China
- Institute of Epilepsy, Beijing Institute for Brain Disorders, Beijing, 100093 China
| |
Collapse
|
5
|
Ehlich J, Migliaccio L, Sahalianov I, Nikić M, Brodský J, Gablech I, Vu XT, Ingebrandt S, Głowacki ED. Direct measurement of oxygen reduction reactions at neurostimulation electrodes. J Neural Eng 2022; 19. [PMID: 35688124 DOI: 10.1088/1741-2552/ac77c0] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Accepted: 06/10/2022] [Indexed: 11/11/2022]
Abstract
Objective. Electric stimulation delivered by implantable electrodes is a key component of neural engineering. While factors affecting long-term stability, safety, and biocompatibility are a topic of continuous investigation, a widely-accepted principle is that charge injection should be reversible, with no net electrochemical products forming. We want to evaluate oxygen reduction reactions (ORR) occurring at different electrode materials when using established materials and stimulation protocols.Approach. As stimulation electrodes, we have tested platinum, gold, tungsten, nichrome, iridium oxide, titanium, titanium nitride, and poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate). We use cyclic voltammetry and voltage-step amperometry in oxygenated versus inert conditions to establish at which potentials ORR occurs, and the magnitudes of diffusion-limited ORR currents. We also benchmark the areal capacitance of each electrode material. We use amperometric probes (Clark-type electrodes) to quantify the O2and H2O2concentrations in the vicinity of the electrode surface. O2and H2O2concentrations are measured while applying DC current, or various biphasic charge-balanced pulses of amplitude in the range 10-30µC cm-2/phase. To corroborate experimental measurements, we employ finite element modelling to recreate 3D gradients of O2and H2O2.Main results. All electrode materials support ORR and can create hypoxic conditions near the electrode surface. We find that electrode materials differ significantly in their onset potentials for ORR, and in the extent to which they produce H2O2as a by-product. A key result is that typical charge-balanced biphasic pulse protocols do lead to irreversible ORR. Some electrodes induce severely hypoxic conditions, others additionally produce an accumulation of hydrogen peroxide into the mM range.Significance. Our findings highlight faradaic ORR as a critical consideration for neural interface devices and show that the established biphasic/charge-balanced approach does not prevent irreversible changes in O2concentrations. Hypoxia and H2O2can result in different (electro)physiological consequences.
Collapse
Affiliation(s)
- Jiří Ehlich
- Bioelectronics Materials and Devices Laboratory, Central European Institute of Technology CEITEC, Brno University of Technology, Purkyňova 123, 61200 Brno, Czech Republic
| | - Ludovico Migliaccio
- Bioelectronics Materials and Devices Laboratory, Central European Institute of Technology CEITEC, Brno University of Technology, Purkyňova 123, 61200 Brno, Czech Republic
| | - Ihor Sahalianov
- Bioelectronics Materials and Devices Laboratory, Central European Institute of Technology CEITEC, Brno University of Technology, Purkyňova 123, 61200 Brno, Czech Republic
| | - Marta Nikić
- Bioelectronics Materials and Devices Laboratory, Central European Institute of Technology CEITEC, Brno University of Technology, Purkyňova 123, 61200 Brno, Czech Republic.,Institute of Neuroelectronics, Technical University of Munich, Munich, Germany
| | - Jan Brodský
- Bioelectronics Materials and Devices Laboratory, Central European Institute of Technology CEITEC, Brno University of Technology, Purkyňova 123, 61200 Brno, Czech Republic
| | - Imrich Gablech
- Bioelectronics Materials and Devices Laboratory, Central European Institute of Technology CEITEC, Brno University of Technology, Purkyňova 123, 61200 Brno, Czech Republic
| | - Xuan Thang Vu
- Institute of Materials in Electrical Engineering 1, RWTH Aachen University, 52074 Aachen, Germany
| | - Sven Ingebrandt
- Institute of Materials in Electrical Engineering 1, RWTH Aachen University, 52074 Aachen, Germany
| | - Eric Daniel Głowacki
- Bioelectronics Materials and Devices Laboratory, Central European Institute of Technology CEITEC, Brno University of Technology, Purkyňova 123, 61200 Brno, Czech Republic
| |
Collapse
|
6
|
Evers J, Sridhar K, Liegey J, Brady J, Jahns H, Lowery M. Stimulation-induced changes at the electrode-tissue interface and their influence on deep brain stimulation. J Neural Eng 2022; 19. [PMID: 35728575 DOI: 10.1088/1741-2552/ac7ad6] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2022] [Accepted: 06/21/2022] [Indexed: 11/12/2022]
Abstract
OBJECTIVE During deep brain stimulation (DBS) the electrode-tissue interface forms a critical path between device and brain tissue. Although changes in the electrical double layer and glial scar can impact stimulation efficacy, the effects of chronic DBS on the electrode-tissue interface have not yet been established. APPROACH In this study, we characterised the electrode-tissue interface surrounding chronically implanted DBS electrodes in rats and compared the impedance and histological properties at the electrode interface in animals that received daily stimulation and in those where no stimulation was applied, up to eight weeks post-surgery. A computational model was developed based on the experimental data, which allowed the dispersive electrical properties of the surrounding encapsulation tissue to be estimated. The model was then used to study the effect of stimulation-induced changes in the electrode-tissue interface on the electric field and neural activation during voltage- and current-controlled stimulation. MAIN RESULTS Incorporating the observed changes in simulations in silico, we estimated the frequency-dependent dielectric properties of the electrical double layer and surrounding encapsulation tissue. Through simulations we show how stimulation-induced changes in the properties of the electrode-tissue interface influence the electric field and alter neural activation during voltage-controlled stimulation. A substantial increase in the number of stimulated collaterals, and their distance from the electrode, was observed during voltage-controlled stimulation with stimulated ETI properties. In vitro examination of stimulated electrodes confirmed that high frequency stimulation leads to desorption of proteins at the electrode interface, with a concomitant reduction in impedance. SIGNIFICANCE The demonstration of stimulation-induced changes in the electrode-tissue interface has important implications for future DBS systems including closed-loop systems where the applied stimulation may change over time. Understanding these changes is particularly important for systems incorporating simultaneous stimulation and sensing, which interact dynamically with brain networks.
Collapse
Affiliation(s)
- J Evers
- School of Electrical and Electronic Engineering, University College Dublin, Engineering Building, UCD Belfield, Dublin, Dublin, 4, IRELAND
| | - K Sridhar
- School of Electrical and Electronic Engineering, University College Dublin, Engineering Building, UCD Belfield, Dublin, Dublin, 4, IRELAND
| | - J Liegey
- School of Electrical and Electronic Engineering, University College Dublin, Engineering Building, UCD Belfield, Dublin, Dublin, 4, IRELAND
| | - J Brady
- School of Veterinary Medicine, University College Dublin, Veterinary Science Center, Dublin, 4, IRELAND
| | - H Jahns
- School of Veterinary Medicine, University College Dublin, Veterinary Science Center, Dublin, 4, IRELAND
| | - M Lowery
- School of Electrical, Electronic & Mechancial Engineering, University College Dublin, Engineering & Materials Science Centre, Belfield, Dublin 4, Dublin, 4, IRELAND
| |
Collapse
|
7
|
Habibi S, Lee HY, Moncada-Hernandez H, Minerick AR. Induction and suppression of cell lysis in an electrokinetic microfluidic system. Electrophoresis 2022; 43:1322-1336. [PMID: 35306692 DOI: 10.1002/elps.202100310] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Revised: 12/23/2021] [Accepted: 01/24/2022] [Indexed: 01/26/2023]
Abstract
The ability to strategically induce or suppress cell lysis is critical for many cellular-level diagnostic and therapeutic applications conducted within electrokinetic microfluidic platforms. The chemical and structural integrity of sub-cellular components is important when inducing cell lysis. However, metal electrodes and electrolytes participate in undesirable electrochemical reactions that alter solution composition and potentially damage protein, RNA, and DNA integrity within device microenvironments. For many biomedical applications, cell viability must be maintained even when device-imposed cell-stressing stimuli (e.g., electrochemical reaction byproducts) are present. In this work, we explored a novel and tunable method to accurately induce or suppress device-imposed artifacts on human red blood cell (RBC) lysis in non-uniform AC electric fields. For precise tunability, a dielectric hafnium oxide (HfO2 ) layer was used to prevent electron transfer between the electrodes and the electric double layer and thus reduce harmful electrochemical reactions. Additionally, a low concentration of Triton X-100 surfactant was explored as a tool to stabilize cell membrane integrity. The extent of hemolysis was studied as a function of time, electrode configuration (T-shaped and star-shaped), cell position, applied non-uniform AC electric field, with uncoated and HfO2 coated electrodes (50 nm), and absence and presence of Triton X-100 (70 µM). Tangible outcomes include a parametric analysis relying upon literature and this work to design, tune, and operate electrokinetic microdevices to intentionally induce or suppress cellular lysis without altering intracellular components. Implications are that devices can be engineered to leverage or minimize device-imposed biological artefacts extending the versatility and utility of electrokinetic diagnostics.
Collapse
Affiliation(s)
- Sanaz Habibi
- Department of Chemical Engineering, Michigan Technological University, Houghton, Michigan, USA
| | - Hwi Yong Lee
- Department of Chemical Engineering, Michigan Technological University, Houghton, Michigan, USA
| | | | - Adrienne R Minerick
- Department of Chemical Engineering, Michigan Technological University, Houghton, Michigan, USA
| |
Collapse
|
8
|
Silvaragi TGB, Vigneswari S, Murugaiyah V, Al-Ashraf A, Ramakrishna S. Exploring polymeric biomaterials in developing neural prostheses. J BIOACT COMPAT POL 2022. [DOI: 10.1177/08839115221075843] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Neuroprosthetics, with a range of applications such as cognitive, auditory, pain relief, recording, motor, and visual prosthetics have emerged as a promising field in recent years. However, poor electrical conductivity, a high disparity between tissue and interfaces and the onset of reactive gliosis post-implantation remains major challenges in the development of neuroprostheses. The choice of biomaterials in designing the neural interfaces’ in neuroprosthetic applications is of high importance, as the overall sustained performance of neuroprosthetic devices is based on the features of materials used for the neural interfaces. Numerous biomaterials, such as metals and carbon-based materials, have been used in neuroprosthetics thus far. Nonetheless, neuroprosthetics made from polymeric biomaterials are in high demand due to their high biocompatibility, conductivity, and biostability. Furthermore, polymeric biomaterials can be used as a hybrid design to overcome the limitations of other co-biomaterials. This article makes an attempt to review the polymeric biomaterials involved in this cutting-edge technology utilized for different purposes such as substrates, coatings, and miniaturization of electrodes, that might help in enriching our understanding on neuroprosthetics.
Collapse
Affiliation(s)
| | - Sevakumaran Vigneswari
- Faculty of Science and Marine Environment, Universiti Malaysia Terengganu, Kuala Terengganu, Terengganu, Malaysia
| | - Vikneswaran Murugaiyah
- Discipline of Pharmacology, School of Pharmaceutical Sciences, Universiti Sains Malaysia, Gelugor, Penang, Malaysia
| | - Amirul Al-Ashraf
- School of Biological Sciences, Universiti Sains Malaysia, Gelugor, Penang, Malaysia
| | - Seeram Ramakrishna
- Department of Mechanical Engineering, Center for Nanofibers and Nanotechnology, National University of Singapore, Singapore, Singapore
| |
Collapse
|
9
|
Doering M, Kieninger J, Urban G, Weltin A. Electrochemical microelectrode degradation monitoring: in situ investigation of platinum corrosion at neutral pH. J Neural Eng 2022; 19. [PMID: 34983028 DOI: 10.1088/1741-2552/ac47da] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2021] [Accepted: 01/04/2022] [Indexed: 11/11/2022]
Abstract
OBJECTIVE The stability of platinum and other noble metal electrodes is critical for neural implants, electrochemical sensors, and energy sources. Beyond the acidic or alkaline environment found in most electrochemical studies, the investigation of electrode corrosion in neutral pH and chloride containing electrolytes is essential, particularly regarding the long-term stability of neural interfaces, such as brain stimulation electrodes or cochlear implants. In addition, the increased use of microfabricated devices demands the investigation of thin-film electrode stability. APPROACH We developed a procedure of electrochemical methods for continuous tracking of electrode degradation in situ over the complete life cycle of platinum thin-film microelectrodes in a unique combination with simultaneous chemical sensing. We used chronoamperometry and cyclic voltammetry to measure electrode surface and analyte redox processes, together with accelerated electrochemical degradation. MAIN RESULTS We compared degradation between thin-film microelectrodes and bulk electrodes, neutral to acidic pH, different pulsing schemes, and the presence of the redox active species oxygen and hydrogen peroxide. Results were confirmed by mechanical profilometry and microscopy to determine material changes on a nanometer scale. We found that electrode degradation is mainly driven by repeated formation and removal of the platinum surface oxide, also within the electrochemical stability window of water. There was no considerable difference between thin-film micro- and macroscopic bulk electrodes or in the presence of reactive species, whereas acidic pH or extending the potential window led to increased degradation. SIGNIFICANCE Our results provide valuable fundamental information on platinum microelectrode degradation under conditions found in biomedical applications. For the first time, we deployed a unified method to report quantitative data on electrode degradation up to a defined endpoint. Our method is a widely applicable framework for comparative long-term studies of sensor and neural interface stability.
Collapse
Affiliation(s)
- Moritz Doering
- University of Freiburg, Georges-Köhler-Allee 103, Freiburg im Breisgau, Baden-Württemberg, 79110, GERMANY
| | - Jochen Kieninger
- University of Freiburg, Georges-Köhler-Allee 103, Freiburg im Breisgau, Baden-Württemberg, 79110, GERMANY
| | - Gerald Urban
- Department of Microsystems Engineering, Albert-Ludwigs-Universitat Freiburg, Georges-Köhler-Allee 103, Freiburg im Breisgau, 79110, GERMANY
| | - Andreas Weltin
- IMTEK - Department of Microsystems Engineering, University of Freiburg, Georges-Köhler-Allee 103, Freiburg im Breisgau, 79110, GERMANY
| |
Collapse
|
10
|
Weltin A, Kieninger J. Electrochemical methods for neural interface electrodes. J Neural Eng 2021; 18. [PMID: 34547734 DOI: 10.1088/1741-2552/ac28d5] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Accepted: 09/21/2021] [Indexed: 11/11/2022]
Abstract
Objective. Neural interfaces often rely on charge transfer processes between electrodes and the tissue or electrolyte. Electrochemical processes are at the core of electrode function and, therefore, the key to neural interface stability, electrode performance characterization, and utilization of electrodes as chemical sensors. Electrochemical techniques offer a variety of options to investigate the charge transfer and electrocatalytic properties of electrodes.Approach. In this tutorial, we present various experiments to illustrate the power of electrochemical methods, serve as a reference and guideline, and stimulate deeper understanding of the subject.Main results.As a basis for the following experiments, we discuss the platinum cyclic voltammogram and focus on understanding surface processes and roughness determination. We highlight the importance of appropriate instrumentation using potentiostats and how strongly it can influence results. We then discuss a number of potential-controlled and current-controlled methods for electrode characterization, including chronocoulometry, chronoamperometry, (active) potentiometry, and chronopotentiometry. They illustrate charge transfer caused by both electrode surface processes and the presence of redox-active species, such as dissolved oxygen and hydrogen, or hydrogen peroxide. We also discuss the electrode potential with respect to a reference electrode under various conditions and how it affects its electrochemical properties like surface state, catalytic properties and capability to transfer charge.Significance.Electrochemical methods are still underutilized in neural engineering, and valuable information is therefore often not accessed. Many studies on electrode characterization would benefit from a more consistent and target-oriented electrochemical methodology and instrumentation. That ranges from the investigation of new materials and processes, over electrode performance assessment to the development of more long-term stable and biocompatible neural interfaces. Ultimately, standardization, consistency and comparability will play a key role in the translation of microtechnology into biomedical and clinical applications.
Collapse
Affiliation(s)
- Andreas Weltin
- Laboratory for Sensors, IMTEK-Department of Microsystems Engineering, University of Freiburg, Freiburg, Germany.,BrainLinks-BrainTools Center, University of Freiburg, Freiburg, Germany
| | - Jochen Kieninger
- Laboratory for Sensors, IMTEK-Department of Microsystems Engineering, University of Freiburg, Freiburg, Germany.,BrainLinks-BrainTools Center, University of Freiburg, Freiburg, Germany
| |
Collapse
|
11
|
Harris AR, Newbold C, Carter P, Cowan R, Wallace GG. Using Chronopotentiometry to Better Characterize the Charge Injection Mechanisms of Platinum Electrodes Used in Bionic Devices. Front Neurosci 2019; 13:380. [PMID: 31118879 PMCID: PMC6508053 DOI: 10.3389/fnins.2019.00380] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2018] [Accepted: 04/02/2019] [Indexed: 11/13/2022] Open
Abstract
The safe charge injection capacity and charge density of neural stimulating electrodes is based on empirical evidence obtained from stimulating feline cortices. Stimulation induced tissue damage may be caused by electrochemical or biological mechanisms. Separating these mechanisms requires greater understanding of charge transfer at the electrode-tissue interface. Clinical devices typically use a biphasic waveform with controlled current. Therefore, the charge injection mechanism and charge injection capacity of platinum was assessed on a commercial potentiostat by chronopotentiometry (controlled current stimulation). Platinum is a non-ideal electrode, charge injection by chronopotentiometry can be passed via capacitive and Faradaic mechanisms. Electrodes were tested under a variety of conditions to assess the impact on charge injection capacity. The change in electrode potential (charge injection capacity) was affected by applied charge density, pulse length, pulse polarity, electrode size, polishing method, electrolyte composition, and oxygen concentration. The safe charge injection capacity and charge density could be increased by changing the electrode-solution composition and stimulation parameters. However, certain conditions (e.g., acid polished electrodes) allowed the electrode to exceed the water electrolysis potential despite the stimulation protocol being deemed safe according to the Shannon plot. Multiple current pulses led to a shift or ratcheting in electrode potential due to changes in the electrode-solution composition. An accurate measure of safe charge injection capacity and charge density of an implantable electrode can only be obtained from suitable conditions (an appropriately degassed electrolyte and clinically relevant electrode structure). Cyclic voltammetric measurement of charge storage capacity can be performed on implantable electrodes, but will not provide information on electrode stability to multiple chronopotentiometric pulses. In contrast, chronopotentiometry will provide details on electrode stability, but the minimum time resolution of typical commercial potentiostats (ms range) is greater than used in a clinical stimulator (μs range) so that extrapolation to short stimulation pulses is required. Finally, an impedance test is typically used to assess clinical electrode performance. The impedance test is also based on a biphasic chronopotentiometic waveform where the measured potential is used to calculate an impedance value. Here it is shown that the measured potential is a function of many parameters (solution composition, electrode area, and surface composition). Subsequently, impedance test results allow electrode comparison and to indicate electrode failure, but use of Ohm's law to calculate an impedance value is not valid.
Collapse
Affiliation(s)
- Alexander R. Harris
- ARC Centre of Excellence for Electromaterials Science, Intelligent Polymer Research Institute, University of Wollongong, Wollongong, NSW, Australia
- The HEARing CRC, University of Melbourne, Melbourne, VIC, Australia
| | - Carrie Newbold
- The HEARing CRC, University of Melbourne, Melbourne, VIC, Australia
- Department of Audiology and Speech Pathology, University of Melbourne, Melbourne, VIC, Australia
| | - Paul Carter
- Cochlear, Ltd., Macquarie University, Sydney, NSW, Australia
| | - Robert Cowan
- The HEARing CRC, University of Melbourne, Melbourne, VIC, Australia
- Department of Audiology and Speech Pathology, University of Melbourne, Melbourne, VIC, Australia
| | - Gordon G. Wallace
- ARC Centre of Excellence for Electromaterials Science, Intelligent Polymer Research Institute, University of Wollongong, Wollongong, NSW, Australia
- The HEARing CRC, University of Melbourne, Melbourne, VIC, Australia
| |
Collapse
|
12
|
Corrosion Study of Implanted Tin Electrodes Using Excessive Electrical Stimulation in Minipigs. METALS 2019. [DOI: 10.3390/met9040389] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
(1) Background: Titanium nitride (TiN) electrodes have been used for implantable stimulation and sensing electrodes for decades. Nevertheless, there still is a discrepancy between the in vitro and in vivo determined safe charge injection limits. This study investigated the consequences of pulsing implanted electrodes beyond the in vivo safe charge injection limits. (2) Methods: The electrodes were implanted for a month and then pulsed at 20 mA and 50 mA and 200 Hz and 400 Hz. Afterwards, the electrodes were investigated using electrochemical and analytical methods to evaluate whether electrode degradation had occurred. (3) Results: Electrochemical tests showed that electrodes that pulsed at 20 mA and 200 Hz (lowest electrical dose) had a significantly lower charge injection capacity and higher impedance than the other used and unused electrodes. (4) Conclusions: The electrodes pulsed at the lowest electrical dose, for which no tissue damage was found, appeared to have degraded. Electrodes pulsed at higher electrical doses for which tissue damage did occur, on the other hand, show no significant degradation in electrochemical tests compared to unused implanted and not implanted electrodes. It is thus clear that the tissue surrounding the electrode has an influence on the charge injection properties of the electrodes and vice versa.
Collapse
|
13
|
Shepherd RK, Carter PM, Enke YL, Wise AK, Fallon JB. Chronic intracochlear electrical stimulation at high charge densities results in platinum dissolution but not neural loss or functional changes in vivo. J Neural Eng 2018; 16:026009. [PMID: 30523828 DOI: 10.1088/1741-2552/aaf66b] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
OBJECTIVE Although there are useful guidelines defining the boundary between damaging and non-damaging electrical stimulation they were derived from acute studies using large surface area electrodes in direct contact with cortical neurons. These parameters are a small subset of the parameters used by neural stimulators. More recently, histological examination of cochleae from patients that were long-term cochlear implant users have shown evidence of particulate platinum (Pt). The pathophysiological effect of Pt within the cochlea is unknown. We examined the response of the cochlea to stimulus levels beyond those regarded as safe, and to evaluate the pathophysiological response of the cochlea following chronic stimulation at charge densities designed to induce Pt corrosion in vivo. APPROACH 19 guinea pigs were systemically deafened and implanted with a cochlear electrode array containing eight Pt electrodes of 0.05, 0.075 or 0.2 mm2 area. Animals were electrically stimulated continuously for 28 d using charge balanced current pulses at charge densities of 400, 267 or 100 µC/cm2/phase. Electrically-evoked auditory brainstem responses (EABRs) were recorded to monitor neural function. On completion of stimulation electrodes were examined using scanning electron microscopy (SEM) and cochleae examined histology. Finally, analysis of Pt was measured using energy dispersive x-ray spectroscopy (EDS) and inductively coupled plasma mass spectrometry (ICP-MS). MAIN RESULTS Compared with unstimulated control electrodes and electrodes stimulated at 100 µC/cm2/phase, stimulation at 267 or 400 µC/cm2/phase resulted in significant Pt corrosion. Cochleae stimulated at these high charge densities contained particulate Pt. The extent of the foreign body response depended on the level of stimulation; cochleae stimulated at 267 or 400 µC/cm2/phase exhibited an extensive tissue response that included a focal region of necrosis close to the electrode. Despite chronic stimulation at high charge densities there was no loss of auditory neurons (ANs) in stimulated cochleae compared with their contralateral controls. Indeed, we report a statistically significant increase in AN density proximal to electrodes stimulated at 267 or 400 µC/cm2/phase. Finally, there was no evidence of a reduction in AN function associated with chronic stimulation at 100, 267 or 400 µC/cm2/phase as evidenced by stable EABR thresholds over the stimulation program. SIGNIFICANCE Chronic electrical stimulation of Pt electrodes at 267 or 400 µC/cm2/phase evoked a vigorous tissue response and produced Pt corrosion products that were located close to the electrode. Despite these changes at the electrode/tissue interface there was no evidence of neural loss or a reduction in neural function.
Collapse
Affiliation(s)
- Robert K Shepherd
- Bionics Institute, St Vincent's Hospital, Melbourne, Australia. Medical Bionics Department, The University of Melbourne, Melbourne, Australia
| | | | | | | | | |
Collapse
|
14
|
Hudak EM, Kumsa DW, Martin HB, Mortimer JT. Electron transfer processes occurring on platinum neural stimulating electrodes: calculated charge-storage capacities are inaccessible during applied stimulation. J Neural Eng 2018; 14:046012. [PMID: 28345534 DOI: 10.1088/1741-2552/aa6945] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
OBJECTIVE Neural prostheses employing platinum electrodes are often constrained by a charge/charge-density parameter known as the Shannon limit. In examining the relationship between charge injection and observed tissue damage, the electrochemistry at the electrode-tissue interface should be considered. The charge-storage capacity (CSC) is often used as a predictor of how much charge an electrode can inject during stimulation, but calculating charge from a steady-state i-E curve (cyclic voltammogram) over the water window misrepresents how electrodes operate during stimulation. We aim to gain insight into why CSC predictions from classic i-E curves overestimate the amount of charge that can be injected during neural stimulation pulsing. APPROACH In this study, we use a standard electrochemical technique to investigate how platinum electrochemistry depends on the potentials accessed by the electrode and on the electrolyte composition. MAIN RESULTS The experiments indicate: (1) platinum electrodes must be subjected to a 'cleaning' procedure in order to expose the maximum number of surface platinum sites for hydrogen adsorption; (2) the 'cleaned' platinum surface will likely revert to an obstructed condition under typical neural stimulation conditions; (3) irreversible oxygen reduction may occur under neural stimulation conditions, so the consequences of this reaction should be considered; and (4) the presence of the chloride ion (Cl-) or proteins (bovine serum albumin) inhibits oxide formation and alters H adsorption. SIGNIFICANCE These observations help explain why traditional CSC calculations overestimate the charge that can be injected during neural stimulation. The results underscore how careful electrochemical examination of the electrode-electrolyte interface can result in more accurate expectations of electrode performance during applied stimulation.
Collapse
Affiliation(s)
- Eric M Hudak
- Department of Chemical and Biomolecular Engineering, Case Western Reserve University, AW Smith Building, Cleveland, OH, United States of America
| | | | | | | |
Collapse
|
15
|
Wissel K, Brandes G, Pütz N, Angrisani GL, Thieleke J, Lenarz T, Durisin M. Platinum corrosion products from electrode contacts of human cochlear implants induce cell death in cell culture models. PLoS One 2018; 13:e0196649. [PMID: 29763442 PMCID: PMC5953457 DOI: 10.1371/journal.pone.0196649] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2017] [Accepted: 04/17/2018] [Indexed: 12/18/2022] Open
Abstract
Despite the technological progress made with cochlear implants (CI), impedances and their diagnosis remain a focus of interest. Increases in impedance have been related to technical defects of the electrode as well as inflammatory and/or fibrosis along the electrode. Recent studies have demonstrated highly increased impedances as the result of corroded platinum (Pt) electrode contacts. This in vitro study examined the effects of Pt ions and compounds generated by corrosion of the electrode contacts of a human CI on cell metabolism. Since traces of solid Pt in surrounding cochlear tissues have been reported, the impact of commercially available Pt nanoparticles (Pt-NP, size 3 nm) on the cell culture model was also determined. For this purpose, the electrode contacts were electrically stimulated in a 0.5% aqueous NaCl solution for four weeks and the mass fraction of the platinum dissolute (Pt-Diss) was determined by mass spectrometry (ICP-MS). Metabolic activity of the murine fibroblasts (NIH 3T3) and the human neuroblastoma (SH-SY5Y) cells was determined using the WST-1 assay following exposure to Pt-Diss and Pt-NP. It was found that 5–50 μg/ml of the Pt-NP did not affect the viability of both cell types. In contrast, 100 μg/ml of the nanoparticles caused significant loss in metabolic activity. Furthermore, transmission electron microscopy (TEM) revealed mitochondrial swelling in both cell types indicating cytotoxicity. Additionally, TEM demonstrated internalized Pt-NP in NIH 3T3 cells in a concentration dependent manner, whereas endocytosis in SH-SY5Y cells was virtually absent. In comparison with the Pt-NP, the corrosion products (Pt-Diss) with concentrations between 1.64 μg/ml and 8.2 μg/ml induced cell death in both cell lines in a concentration dependent manner. TEM imaging revealed both mitochondrial disintegration and swelling of the endoplasmic reticulum, suggesting that Pt ions trigger cytotoxicity in both NIH 3T3 and SH-SY5Y cell lines by interacting with the respiratory chain.
Collapse
Affiliation(s)
- Kirsten Wissel
- Department of Otorhinolaryngology, Hannover Medical School, Hannover, Germany
- Cluster of Excellence ‘Hearing 4 all’, NIFE, Hannover, Germany
- * E-mail:
| | - Gudrun Brandes
- Institute of Neuroanatomy and Cell Biology, Center of Anatomy and Cell Biology, Hannover Medical School, Hannover, Germany
| | - Nils Pütz
- Department of Otorhinolaryngology, Hannover Medical School, Hannover, Germany
- Biotechnology Center, TU Dresden, Dresden, Germany
| | | | - Jan Thieleke
- Institute of Inorganic Chemistry, Leibniz University Hannover, Hannover, Germany
| | - Thomas Lenarz
- Department of Otorhinolaryngology, Hannover Medical School, Hannover, Germany
- Cluster of Excellence ‘Hearing 4 all’, NIFE, Hannover, Germany
| | - Martin Durisin
- Department of Otorhinolaryngology, Hannover Medical School, Hannover, Germany
| |
Collapse
|
16
|
Kumsa D, Hudak EM, Montague FW, Kelley SC, Untereker DF, Hahn BP, Condit C, Cholette M, Lee H, Bardot D, Takmakov P. Electrical neurostimulation with imbalanced waveform mitigates dissolution of platinum electrodes. J Neural Eng 2016; 13:054001. [PMID: 27650936 PMCID: PMC5565726 DOI: 10.1088/1741-2560/13/5/054001] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
OBJECTIVE Electrical neurostimulation has traditionally been limited to the use of charge-balanced waveforms. Charge-imbalanced and monophasic waveforms are not used to deliver clinical therapy, because it is believed that these stimulation paradigms may generate noxious electrochemical species that cause tissue damage. APPROACH In this study, we investigated the dissolution of platinum as one of such irreversible reactions over a range of charge densities up to 160 μC cm-2 with current-controlled first phase, capacitive discharge second phase waveforms of both cathodic-first and anodic-first polarity. We monitored the concentration of platinum in solution under different stimulation delivery conditions including charge-balanced, charge-imbalanced, and monophasic pulses. MAIN RESULTS We observed that platinum dissolution decreased during charge-imbalanced and monophasic stimulation when compared to charge-balanced waveforms. SIGNIFICANCE This observation provides an opportunity to re-evaluate the charge-balanced waveform as the primary option for sustainable neural stimulation.
Collapse
Affiliation(s)
- Doe Kumsa
- Division of Biology, Chemistry, and Materials Science, Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, US Food and Drug Administration, White Oak Federal Research Center, Silver Spring, MD, USA. Medical Device Innovation Consortium, St. Louis Park, MN, USA
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
17
|
Meijs S, Fjorback M, Jensen C, Sørensen S, Rechendorff K, Rijkhoff NJM. Influence of fibrous encapsulation on electro-chemical properties of TiN electrodes. Med Eng Phys 2016; 38:468-76. [PMID: 26997562 DOI: 10.1016/j.medengphy.2016.02.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2015] [Revised: 02/10/2016] [Accepted: 02/16/2016] [Indexed: 10/22/2022]
Abstract
The aim of this study was to investigate how the electrochemical properties of porous titanium nitride stimulation electrode are affected by fibrous encapsulation in vivo. Electrochemical impedance spectroscopy (EIS), cyclic voltammetry and voltage transient (VT) measurements were performed in vivo and in phosphate buffered saline, where the encapsulation process is absent. EIS was used as a non-invasive measurement to follow the inflammation, healing and encapsulation process. EIS showed that the healing and encapsulation process lasted 3-4 weeks. The VTs increased during the first 3-4 weeks, after which they stabilized. The charge storage capacity (CSC) decreased most during the first 3-4 weeks. The increasing VTs and decreasing CSC during the first 3-4 weeks after implantation of the in vivo electrodes seem related to healing and fibrous encapsulation. It is suggested that the charge injection pathway during the encapsulation process changes, which implies that charge injection limits are underestimated with conventional methods.
Collapse
Affiliation(s)
- Suzan Meijs
- Center for Sensory-Motor Interaction, Aalborg University, Fredrik Bajersvej 7E, 9220 Aalborg, Denmark.
| | - Morten Fjorback
- Neurodan A/S, Aalborg, Denmark; Bang & Olufsen Medicom A/S, Struer, Denmark
| | - Carina Jensen
- Neurodan A/S, Aalborg, Denmark; Aalborg University Hospital, Aalborg, Denmark
| | | | | | - Nico J M Rijkhoff
- Center for Sensory-Motor Interaction, Aalborg University, Fredrik Bajersvej 7E, 9220 Aalborg, Denmark
| |
Collapse
|
18
|
Howlader MMR, Ul Alam A, Sharma RP, Deen MJ. Materials analyses and electrochemical impedance of implantable metal electrodes. Phys Chem Chem Phys 2015; 17:10135-45. [PMID: 25790136 DOI: 10.1039/c4cp05899b] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Implantable electrodes with high flexibility, high mechanical fixation and low electrochemical impedance are desirable for neuromuscular activation because they provide safe, effective and stable stimulation. In this paper, we report on detailed materials and electrical analyses of three metal implantable electrodes - gold (Au), platinum (Pt) and titanium (Ti) - using X-ray photoelectron spectroscopy (XPS), scanning acoustic microscopy, drop shape analysis and electrochemical impedance spectroscopy. We investigated the cause of changes in electrochemical impedance of long-term immersed Au, Pt and Ti electrodes on liquid crystal polymers (LCPs) in phosphate buffered saline (PBS). We analyzed the surface wettability, surface and interface defects and the elemental depth profile of the electrode-adhesion layers on the LCP. The impedance of the electrodes decreased at lower frequencies, but increased at higher frequencies compared with that of the short-term immersion. The increase of impedances was influenced by the oxidation of the electrode/adhesion-layers that affected the double layer capacitance behavior of the electrode/PBS. The oxidation of the adhesion layer for all the electrodes was confirmed by XPS. Alkali ions (sodium) were adsorbed on the Au and Pt surfaces, but diffused into the Ti electrode and LCPs. The Pt electrode showed a higher sensitivity to surface and interface defects than that of Ti and Au electrodes. These findings may be useful when designing electrodes for long-term implantable devices.
Collapse
Affiliation(s)
- Matiar M R Howlader
- Department of Electrical and Computer Engineering, McMaster University, Hamilton, Ontario L8S 4K1, Canada.
| | | | | | | |
Collapse
|
19
|
Leung RT, Shivdasani MN, Nayagam DAX, Shepherd RK. In Vivo and In Vitro Comparison of the Charge Injection Capacity of Platinum Macroelectrodes. IEEE Trans Biomed Eng 2015; 62:849-57. [DOI: 10.1109/tbme.2014.2366514] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
|
20
|
Ahadian S, Ramón-Azcón J, Ostrovidov S, Camci-Unal G, Kaji H, Ino K, Shiku H, Khademhosseini A, Matsue T. A contactless electrical stimulator: application to fabricate functional skeletal muscle tissue. Biomed Microdevices 2013; 15:109-15. [PMID: 22965808 DOI: 10.1007/s10544-012-9692-1] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Engineered skeletal muscle tissues are ideal candidates for applications in drug screening systems, bio-actuators, and as implantable constructs in tissue engineering. Electrical field stimulation considerably improves the differentiation of muscle cells to muscle myofibers. Currently used electrical stimulators often use direct contact of electrodes with tissue constructs or their culture medium, which may cause hydrolysis of the culture medium, joule heating of the medium, contamination of the culture medium due to products of electrodes corrosion, and surface fouling of electrodes. Here, we used an interdigitated array of electrodes combined with an isolator coverslip as a contactless platform to electrically stimulate engineered muscle tissue, which eliminates the aforementioned problems. The effective stimulation of muscle myofibers using this device was demonstrated in terms of contractile activity and higher maturation as compared to muscle tissues without applying the electrical field. Due to the wide array of potential applications of electrical stimulation to two- and three-dimensional (2D and 3D) cell and tissue constructs, this device could be of great interest for a variety of biological applications as a tool to create noninvasive, safe, and highly reproducible electric fields.
Collapse
Affiliation(s)
- Samad Ahadian
- WPI-Advanced Institute for Materials Research, Tohoku University, Sendai, 980-8577, Japan
| | | | | | | | | | | | | | | | | |
Collapse
|
21
|
Chen L, Lv C, Chen J, Bi S. Numerical simulation study on cyclic reciprocal derivative chronopotentiometry of reversible electrode reaction coupled with Langmuir adsorption. Electrochim Acta 2013. [DOI: 10.1016/j.electacta.2012.12.123] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
|
22
|
|
23
|
Nam KM, Shin DH, Jung N, Joo MG, Jeon S, Park SM, Chang BY. Development of Galvanostatic Fourier Transform Electrochemical Impedance Spectroscopy. Anal Chem 2013; 85:2246-52. [DOI: 10.1021/ac303108n] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Affiliation(s)
| | | | - Namchul Jung
- Department of Chemical Engineering, Pohang University of Science and Technology, San 31
Namgu Hyojadong, Pohang, Korea
| | | | - Sangmin Jeon
- Department of Chemical Engineering, Pohang University of Science and Technology, San 31
Namgu Hyojadong, Pohang, Korea
| | - Su-Moon Park
- Interdisciplinary School of
Green Energy, Ulsan National Institute of Science and Engineering, Ulsan 689-805, Korea
| | | |
Collapse
|
24
|
Musa S, Rand DR, Cott DJ, Loo J, Bartic C, Eberle W, Nuttin B, Borghs G. Bottom-up SiO2 embedded carbon nanotube electrodes with superior performance for integration in implantable neural microsystems. ACS NANO 2012; 6:4615-4628. [PMID: 22551016 DOI: 10.1021/nn201609u] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The reliable integration of carbon nanotube (CNT) electrodes in future neural probes requires a proper embedding of the CNTs to prevent damage and toxic contamination during fabrication and also to preserve their mechanical integrity during implantation. Here we describe a novel bottom-up embedding approach where the CNT microelectrodes are encased in SiO(2) and Parylene C with lithographically defined electrode openings. Vertically aligned CNTs are grown on microelectrode arrays using low-temperature plasma-enhanced chemical vapor deposition compatible with wafer-scale CMOS processing. Electrodes with 5, 10, and 25 μm diameter are realized. The CNT electrodes are characterized by electrochemical impedance spectroscopy and cyclic voltammetry and compared against cofabricated Pt and TiN electrodes. The superior performance of the CNTs in terms of impedance (≤4.8 ± 0.3 kΩ at 1 kHz) and charge-storage capacity (≥513.9 ± 61.6 mC/cm(2)) is attributed to an increased wettability caused by the removal of the SiO(2) embedding in buffered hydrofluoric acid. Infrared spectroscopy reveals an unaltered chemical fingerprint of the CNTs after fabrication. Impedance monitoring during biphasic current pulsing with increasing amplitudes provides clear evidence of the onset of gas evolution at CNT electrodes. Stimulation is accordingly considered safe for charge densities ≤40.7 mC/cm(2). In addition, prolonged stimulation with 5000 biphasic current pulses at 8.1, 40.7, and 81.5 mC/cm(2) increases the CNT electrode impedance at 1 kHz only by 5.5, 1.2, and 12.1%, respectively. Finally, insertion of CNT electrodes with and without embedding into rat brains demonstrates that embedded CNTs are mechanically more stable than non-embedded CNTs.
Collapse
Affiliation(s)
- Silke Musa
- Imec, Kapeldreef 75, 3001 Heverlee, Belgium.
| | | | | | | | | | | | | | | |
Collapse
|