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Shah DD, Carter P, Shivdasani MN, Fong N, Duan W, Esrafilzadeh D, Poole-Warren LA, Aregueta Robles UA. Deciphering platinum dissolution in neural stimulation electrodes: Electrochemistry or biology? Biomaterials 2024; 309:122575. [PMID: 38677220 DOI: 10.1016/j.biomaterials.2024.122575] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2024] [Revised: 03/28/2024] [Accepted: 04/13/2024] [Indexed: 04/29/2024]
Abstract
Platinum (Pt) is the metal of choice for electrodes in implantable neural prostheses like the cochlear implants, deep brain stimulating devices, and brain-computer interfacing technologies. However, it is well known since the 1970s that Pt dissolution occurs with electrical stimulation. More recent clinical and in vivo studies have shown signs of corrosion in explanted electrode arrays and the presence of Pt-containing particulates in tissue samples. The process of degradation and release of metallic ions and particles can significantly impact on device performance. Moreover, the effects of Pt dissolution products on tissue health and function are still largely unknown. This is due to the highly complex chemistry underlying the dissolution process and the difficulty in decoupling electrical and chemical effects on biological responses. Understanding the mechanisms and effects of Pt dissolution proves challenging as the dissolution process can be influenced by electrical, chemical, physical, and biological factors, all of them highly variable between experimental settings. By evaluating comprehensive findings on Pt dissolution mechanisms reported in the fuel cell field, this review presents a critical analysis of the possible mechanisms that drive Pt dissolution in neural stimulation in vitro and in vivo. Stimulation parameters, such as aggregate charge, charge density, and electrochemical potential can all impact the levels of dissolved Pt. However, chemical factors such as electrolyte types, dissolved gases, and pH can all influence dissolution, confounding the findings of in vitro studies with multiple variables. Biological factors, such as proteins, have been documented to exhibit a mitigating effect on the dissolution process. Other biological factors like cells and fibro-proliferative responses, such as fibrosis and gliosis, impact on electrode properties and are suspected to impact on Pt dissolution. However, the relationship between electrical properties of stimulating electrodes and Pt dissolution remains contentious. Host responses to Pt degradation products are also controversial due to the unknown chemistry of Pt compounds formed and the lack of understanding of Pt distribution in clinical scenarios. The cytotoxicity of Pt produced via electrical stimulation appears similar to Pt-based compounds, including hexachloroplatinates and chemotherapeutic agents like cisplatin. While the levels of Pt produced under clinical and acute stimulation regimes were typically an order of magnitude lower than toxic concentrations observed in vitro, further research is needed to accurately assess the mass balance and type of Pt produced during long-term stimulation and its impact on tissue response. Finally, approaches to mitigating the dissolution process are reviewed. A wide variety of approaches, including stimulation strategies, coating electrode materials, and surface modification techniques to avoid excess charge during stimulation and minimise tissue response, may ultimately support long-term and safe operation of neural stimulating devices.
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Affiliation(s)
- Dhyey Devashish Shah
- Graduate School of Biomedical Engineering, University of New South Wales, Sydney, Australia
| | - Paul Carter
- Cochlear Ltd, Macquarie University, NSW, Australia
| | | | - Nicole Fong
- Cochlear Ltd, Macquarie University, NSW, Australia
| | - Wenlu Duan
- Graduate School of Biomedical Engineering, University of New South Wales, Sydney, Australia
| | - Dorna Esrafilzadeh
- Graduate School of Biomedical Engineering, University of New South Wales, Sydney, Australia
| | - Laura Anne Poole-Warren
- Graduate School of Biomedical Engineering, University of New South Wales, Sydney, Australia; The Tyree Foundation Institute of Health Engineering, University of New South Wales, Sydney, Australia.
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Abbott CJ, Allen PJ, Williams CE, Williams RA, Epp SB, Burns O, Thomas R, Harrison M, Thien PC, Saunders A, McGowan C, Sloan C, Luu CD, Nayagam DAX. Chronic electrical stimulation with a peripheral suprachoroidal retinal implant: a preclinical safety study of neuroprotective stimulation. Front Cell Dev Biol 2024; 12:1422764. [PMID: 38966426 PMCID: PMC11222648 DOI: 10.3389/fcell.2024.1422764] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2024] [Accepted: 06/05/2024] [Indexed: 07/06/2024] Open
Abstract
Purpose Extraocular electrical stimulation is known to provide neuroprotection for retinal cells in retinal and optic nerve diseases. Currently, the treatment approach requires patients to set up extraocular electrodes and stimulate potentially weekly due to the lack of an implantable stimulation device. Hence, a minimally-invasive implant was developed to provide chronic electrical stimulation to the retina, potentially improving patient compliance for long-term use. The aim of the present study was to determine the surgical and stimulation safety of this novel device designed for neuroprotective stimulation. Methods Eight normally sighted adult feline subjects were monocularly implanted in the suprachoroidal space in the peripheral retina for 9-39 weeks. Charge balanced, biphasic, current pulses (100 μA, 500 µs pulse width and 50 pulses/s) were delivered continuously to platinum electrodes for 3-34 weeks. Electrode impedances were measured hourly. Retinal structure and function were assessed at 1-, 2-, 4-, 6- and 8-month using electroretinography, optical coherence tomography and fundus photography. Retina and fibrotic thickness were measured from histological sections. Randomized, blinded histopathological assessments of stimulated and non-stimulated retina were performed. Results All subjects tolerated the surgical and stimulation procedure with no evidence of discomfort or unexpected adverse outcomes. The device position was stable after a post-surgery settling period. Median electrode impedance remained within a consistent range (5-10 kΩ) over time. There was no change in retinal thickness or function relative to baseline and fellow eyes. Fibrotic capsule thickness was equivalent between stimulated and non-stimulated tissue and helps to hold the device in place. There was no scarring, insertion trauma, necrosis, retinal damage or fibroblastic response in any retinal samples from implanted eyes, whilst 19% had a minimal histiocytic response, 19% had minimal to mild acute inflammation and 28% had minimal to mild chronic inflammation. Conclusion Chronic suprathreshold electrical stimulation of the retina using a minimally invasive device evoked a mild tissue response and no adverse clinical findings. Peripheral suprachoroidal electrical stimulation with an implanted device could potentially be an alternative approach to transcorneal electrical stimulation for delivering neuroprotective stimulation.
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Affiliation(s)
- Carla J. Abbott
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, East Melbourne, VIC, Australia
- Department of Surgery (Ophthalmology), University of Melbourne, East Melbourne, VIC, Australia
| | - Penelope J. Allen
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, East Melbourne, VIC, Australia
- Department of Surgery (Ophthalmology), University of Melbourne, East Melbourne, VIC, Australia
- Vitreoretinal Unit, Royal Victorian Eye and Ear Hospital, East Melbourne, VIC, Australia
| | - Chris E. Williams
- Bionics Institute, East Melbourne, VIC, Australia
- Medical Bionics Department, University of Melbourne, Fitzroy, VIC, Australia
| | - Richard A. Williams
- Department of Clinical Pathology, University of Melbourne, Parkville, VIC, Australia
- Dorevitch Pathology, Heidelberg, VIC, Australia
| | | | - Owen Burns
- Bionics Institute, East Melbourne, VIC, Australia
| | - Ross Thomas
- Bionics Institute, East Melbourne, VIC, Australia
| | | | - Patrick C. Thien
- Bionics Institute, East Melbourne, VIC, Australia
- Medical Bionics Department, University of Melbourne, Fitzroy, VIC, Australia
| | | | | | | | - Chi D. Luu
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, East Melbourne, VIC, Australia
- Department of Surgery (Ophthalmology), University of Melbourne, East Melbourne, VIC, Australia
| | - David A. X. Nayagam
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, East Melbourne, VIC, Australia
- Department of Clinical Pathology, University of Melbourne, Parkville, VIC, Australia
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Abstract
Inherited ocular diseases comprise a heterogeneous group of rare and complex diseases, including inherited retinal diseases (IRDs) and inherited optic neuropathies. Recent success in adeno-associated virus-based gene therapy, voretigene neparvovec (Luxturna®) for RPE65-related IRDs, has heralded rapid evolution in gene therapy platform technologies and strategies, from gene augmentation to RNA editing, as well as gene agnostic approaches such as optogenetics. This review discusses the fundamentals underlying the mode of inheritance, natural history studies and clinical trial outcomes, as well as current and emerging therapies covering gene therapy strategies, cell-based therapies and bionic vision.
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Affiliation(s)
- Hwei Wuen Chan
- Department of Ophthalmology, National University Hospital, Singapore,Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore,Correspondence: Dr Hwei Wuen Chan, Assistant Professor, Department of Ophthalmology (Eye), Yong Loo Lin School of Medicine, National University of Singapore, 1E Kent Ridge Road, NUHS Tower Block, Level 7, 119228, Singapore. E-mail:
| | - Jaslyn Oh
- Department of Ophthalmology, National University Hospital, Singapore
| | - Bart Leroy
- Department of Ophthalmology, Ghent University Hospital, Ghent, Belgium,Department of Head and Skin, Ghent University, Ghent, Belgium,Center for Medical Genetics, Ghent University Hospital, Ghent, Belgium,Division of Ophthalmology, Children's Hospital of Philadelphia, Philadelphia, PA, USA
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Muqit MMK, Mer YL, Holz FG, Sahel JA. Long-term observations of macular thickness after subretinal implantation of a photovoltaic prosthesis in patients with atrophic age-related macular degeneration. J Neural Eng 2022; 19:10.1088/1741-2552/ac9645. [PMID: 36174540 PMCID: PMC9684097 DOI: 10.1088/1741-2552/ac9645] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2022] [Accepted: 09/29/2022] [Indexed: 11/12/2022]
Abstract
Objective. Subretinal prostheses electrically stimulate the residual inner retinal neurons to partially restore vision. We investigated the changes in neurosensory macular structures and it is thickness associated with subretinal implantation in geographic atrophy (GA) secondary to age-related macular degeneration (AMD).Approach. Using optical coherence tomography, changes in distance between electrodes and retinal inner nuclear layer (INL) as well as alterations in thickness of retinal layers were measured over time above and near the subretinal chip implanted within the atrophic area. Retinal thickness (RT) was quantified across the implant surface and edges as well as outside the implant zone to compare with the natural macular changes following subretinal surgery, and the natural course of dry AMD.Main results. GA was defined based on complete retinal pigment epithelium and outer retinal atrophy (cRORA). Based on the analysis of three patients with subretinal implantation, we found that the distance between the implant and the target cells was stable over the long-term follow-up. Total RT above the implant decreased on average, by 39 ± 12µm during 3 months post-implantation, but no significant changes were observed after that, up to 36 months of the follow-up. RT also changed near the temporal entry point areas outside the implantation zone following the surgical trauma of retinal detachment. There was no change in the macula cRORA nasal to the implanted zone, where there was no surgical trauma or manipulation.Significance. The surgical delivery of the photovoltaic subretinal implant causes minor RT changes that settle after 3 months, and then remain stable over long-term with no adverse structural or functional effects. Distance between the implant and the INL remains stable up to 36 months of the follow-up.
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Affiliation(s)
- Mahiul M K Muqit
- Vitreoretinal Service, Moorfields Eye Hospital, London, United Kingdom
- Institute of Ophthalmology, University College London, London, United Kingdom
| | - Yannick Le Mer
- Department of Ophthalmology, Fondation Ophtalmologique A. de Rothschild, Paris, France
| | - Frank G Holz
- University of Bonn, Department of Ophthalmology, Bonn, Germany
| | - José A Sahel
- Department of Ophthalmology, Fondation Ophtalmologique A. de Rothschild, Paris, France
- Clinical Investigation Center INSERM-DGOS 1423, Quinze-Vingts National Eye Hospital, Paris, France
- Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, PA, United States of America
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Zeng Q, Yu S, Fan Z, Huang Y, Song B, Zhou T. Nanocone-Array-Based Platinum-Iridium Oxide Neural Microelectrodes: Structure, Electrochemistry, Durability and Biocompatibility Study. NANOMATERIALS (BASEL, SWITZERLAND) 2022; 12:nano12193445. [PMID: 36234573 PMCID: PMC9565584 DOI: 10.3390/nano12193445] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2022] [Revised: 09/23/2022] [Accepted: 09/28/2022] [Indexed: 05/14/2023]
Abstract
Neural interfaces provide a window for bio-signal modulation and recording with the assistance of neural microelectrodes. However, shrinking the size of electrodes results in high electrochemical impedance and low capacitance, thus limiting the stimulation/recording efficiency. In order to achieve critical stability and low power consumption, here, nanocone-shaped platinum (Pt) with an extensive surface area is proposed as an adhesive layer on a bare Pt substrate, followed by the deposition of a thin layer of iridium oxide (IrOx) to fabricate high-performance nanocone-array-based Pt-IrOx neural microelectrodes (200 μm in diameter). A uniform nanocone-shaped Pt with significant roughness is created via controlling the ratio of NH4+ and Pt4+ ions in the electrolyte, which can be widely applicable for batch production on multichannel flexible microelectrode arrays (fMEAs) and various substrates with different dimensions. The Pt-IrOx nanocomposite-coated microelectrode presents a significantly low impedance down to 0.72 ± 0.04 Ω cm2 at 1 kHz (reduction of ~92.95%). The cathodic charge storage capacity (CSCc) and charge injection capacity (CIC) reaches up to 52.44 ± 2.53 mC cm-2 and 4.39 ± 0.36 mC cm-2, respectively. Moreover, superior chronic stability and biocompatibility are also observed. The modified microelectrodes significantly enhance the adhesion of microglia, the major immune cells in the central nervous system. Therefore, such a coating strategy presents great potential for biomedical and other practical applications.
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Affiliation(s)
- Qi Zeng
- Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China
- College of Physics and Optoelectronic Engineering, Shenzhen University, Shenzhen 518061, China
- Correspondence: (Q.Z.); (B.S.); (T.Z.)
| | - Shoujun Yu
- Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China
| | - Zihui Fan
- Institutes of Biomedical Sciences, Fudan University, Shanghai 200032, China
| | - Yubin Huang
- Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China
| | - Bing Song
- Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China
- Correspondence: (Q.Z.); (B.S.); (T.Z.)
| | - Tian Zhou
- Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China
- Correspondence: (Q.Z.); (B.S.); (T.Z.)
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Abbott CJ, Baglin EK, Kolic M, McGuinness MB, Titchener SA, Young KA, Yeoh J, Luu CD, Ayton LN, Petoe MA, Allen PJ. Interobserver Agreement of Electrode to Retina Distance Measurements in a Second-Generation (44-Channel) Suprachoroidal Retinal Prosthesis. Transl Vis Sci Technol 2022; 11:4. [PMID: 36066322 PMCID: PMC9463715 DOI: 10.1167/tvst.11.9.4] [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] [Indexed: 11/24/2022] Open
Abstract
Purpose The electrode to retina (ER) distance is an important contributory factor to the safety and efficacy of a suprachoroidal retinal prosthesis. Measuring ER distance may be performed by different observers during multisite studies. The aim of this study was to assess the interobserver agreement in measuring ER distance. Methods Three independent, trained observers measured ER distance from the center of each suprachoroidal electrode to the inner retinal pigment epithelium in spectral-domain optical coherence tomography (SD-OCT) B-scans. A total of 121 ER distance measurements from 77 B-scans collected over 5 months from one subject implanted with a second-generation 44-channel suprachoroidal retinal prosthesis (NCT03406416) were made by each observer. Results ER distance ranged from 208 to 509 µm. Pearson's correlation coefficient (ρ) showed agreement of 0.99 (95% confidence interval [CI] = 0.98–0.99) in measuring ER for each pairwise comparison. The mean difference in ER distance between observers ranged from 2.4 to 6.4 µm with pairwise limits of agreement (95% CI) of ±20 µm (5.5% of mean). Intraclass correlation coefficient (ICC) showed agreement of 0.98 (95% CI = 0.97–0.99) between observers. Conclusions There is high agreement in measuring ER distances for suprachoroidal retinal prostheses using our systematic approach between multiple, trained observers, supporting the use of a single observer for each image. Translational Relevance High interobserver agreement outcomes indicate that multiple, trained observers can be used to take ER measurements across different images in suprachoroidal retinal prosthesis studies. This improves multisite study efficiency and gives confidence in interpreting results relating to the safety and efficacy of suprachoroidal retinal prostheses.
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Affiliation(s)
- Carla J Abbott
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Victoria, Australia.,Department of Surgery (Ophthalmology), University of Melbourne, Victoria, Australia
| | - Elizabeth K Baglin
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Victoria, Australia
| | - Maria Kolic
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Victoria, Australia
| | - Myra B McGuinness
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Victoria, Australia.,Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, University of Melbourne, Victoria, Australia
| | - Samuel A Titchener
- Bionics Institute of Australia, Victoria, Australia.,Medical Bionics Department, University of Melbourne, Victoria, Australia
| | - Kiera A Young
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Victoria, Australia
| | - Jonathan Yeoh
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Victoria, Australia
| | - Chi D Luu
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Victoria, Australia.,Department of Surgery (Ophthalmology), University of Melbourne, Victoria, Australia
| | - Lauren N Ayton
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Victoria, Australia.,Department of Surgery (Ophthalmology), University of Melbourne, Victoria, Australia.,Department of Optometry and Vision Sciences, University of Melbourne, Australia
| | - Matthew A Petoe
- Bionics Institute of Australia, Victoria, Australia.,Medical Bionics Department, University of Melbourne, Victoria, Australia
| | - Penelope J Allen
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Victoria, Australia.,Department of Surgery (Ophthalmology), University of Melbourne, Victoria, Australia
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7
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Wang J, Zhao R, Li P, Fang Z, Li Q, Han Y, Zhou R, Zhang Y. Clinical Progress and Optimization of Information Processing in Artificial Visual Prostheses. SENSORS (BASEL, SWITZERLAND) 2022; 22:6544. [PMID: 36081002 PMCID: PMC9460383 DOI: 10.3390/s22176544] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/26/2022] [Revised: 08/22/2022] [Accepted: 08/26/2022] [Indexed: 06/15/2023]
Abstract
Visual prostheses, used to assist in restoring functional vision to the visually impaired, convert captured external images into corresponding electrical stimulation patterns that are stimulated by implanted microelectrodes to induce phosphenes and eventually visual perception. Detecting and providing useful visual information to the prosthesis wearer under limited artificial vision has been an important concern in the field of visual prosthesis. Along with the development of prosthetic device design and stimulus encoding methods, researchers have explored the possibility of the application of computer vision by simulating visual perception under prosthetic vision. Effective image processing in computer vision is performed to optimize artificial visual information and improve the ability to restore various important visual functions in implant recipients, allowing them to better achieve their daily demands. This paper first reviews the recent clinical implantation of different types of visual prostheses, summarizes the artificial visual perception of implant recipients, and especially focuses on its irregularities, such as dropout and distorted phosphenes. Then, the important aspects of computer vision in the optimization of visual information processing are reviewed, and the possibilities and shortcomings of these solutions are discussed. Ultimately, the development direction and emphasis issues for improving the performance of visual prosthesis devices are summarized.
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Affiliation(s)
- Jing Wang
- School of Information, Shanghai Ocean University, Shanghai 201306, China
- Key Laboratory of Fishery Information, Ministry of Agriculture, Shanghai 200335, China
| | - Rongfeng Zhao
- School of Information, Shanghai Ocean University, Shanghai 201306, China
| | - Peitong Li
- School of Information, Shanghai Ocean University, Shanghai 201306, China
| | - Zhiqiang Fang
- School of Information, Shanghai Ocean University, Shanghai 201306, China
| | - Qianqian Li
- School of Information, Shanghai Ocean University, Shanghai 201306, China
| | - Yanling Han
- School of Information, Shanghai Ocean University, Shanghai 201306, China
| | - Ruyan Zhou
- School of Information, Shanghai Ocean University, Shanghai 201306, China
| | - Yun Zhang
- School of Information, Shanghai Ocean University, Shanghai 201306, China
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