1
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Bhuckory MB, Wang BY, Chen ZC, Shin A, Pham-Howard D, Shah S, Monkongpitukkul N, Galambos L, Kamins T, Mathieson K, Palanker D. 3D electronic implants in subretinal space: Long-term follow-up in rodents. Biomaterials 2024; 311:122674. [PMID: 38897028 DOI: 10.1016/j.biomaterials.2024.122674] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2024] [Revised: 06/12/2024] [Accepted: 06/15/2024] [Indexed: 06/21/2024]
Abstract
Clinical results with photovoltaic subretinal prosthesis (PRIMA) demonstrated restoration of sight via electrical stimulation of the interneurons in degenerated retina, with resolution matching the 100 μm pixel size. Since scaling the pixels below 75 μm in the current bipolar planar geometry will significantly limit the penetration depth of the electric field and increase stimulation threshold, we explore the possibility of using smaller pixels based on a novel 3-dimensional honeycomb-shaped design. We assessed the long-term biocompatibility and stability of these arrays in rats by investigating the anatomical integration of the retina with flat and 3D implants and response to electrical stimulation over lifetime - up to 32-36 weeks post-implantation in aged rats. With both flat and 3D implants, signals elicited in the visual cortex decreased after the day of implantation by more than 3-fold, and gradually recovered over the next 12-16 weeks. With 25 μm high honeycomb walls, the majority of bipolar cells migrate into the wells, while amacrine and ganglion cells remain above the cavities, which is essential for selective network-mediated stimulation of the retina. Retinal thickness and full-field stimulation threshold with 40 μm-wide honeycomb pixels were comparable to those with planar devices - 0.05 mW/mm2 with 10 ms pulses. However, fewer cells from the inner nuclear layer migrated into the 20 μm-wide wells, and stimulation threshold increased over 12-16 weeks, before stabilizing at about 0.08 mW/mm2. Such threshold is still significantly lower than 1.8 mW/mm2 with a previous design of flat bipolar pixels, confirming the promise of the 3D honeycomb-based approach to high resolution subretinal prosthesis.
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Affiliation(s)
- Mohajeet B Bhuckory
- Department of Ophthalmology, Stanford University, Stanford, CA, USA; Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA, USA.
| | - Bing-Yi Wang
- Department of Physics, Stanford University, Stanford, CA, USA
| | - Zhijie C Chen
- Department of Electrical Engineering, Stanford University, Stanford, CA, USA
| | - Andrew Shin
- Department of Material Science, Stanford University, Stanford, CA, USA
| | - Davis Pham-Howard
- Department of Ophthalmology, Stanford University, Stanford, CA, USA; Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA, USA
| | - Sarthak Shah
- Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA, USA
| | - Nicharee Monkongpitukkul
- Department of Ophthalmology, Stanford University, Stanford, CA, USA; Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA, USA
| | - Ludwig Galambos
- Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA, USA
| | - Theodore Kamins
- Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA, USA; Department of Electrical Engineering, Stanford University, Stanford, CA, USA
| | - Keith Mathieson
- Department of Physics, Institute of Photonics, University of Strathclyde, Glasgow, Scotland, UK
| | - Daniel Palanker
- Department of Ophthalmology, Stanford University, Stanford, CA, USA; Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA, USA
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2
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Liu X, Gong Y, Jiang Z, Stevens T, Li W. Flexible high-density microelectrode arrays for closed-loop brain-machine interfaces: a review. Front Neurosci 2024; 18:1348434. [PMID: 38686330 PMCID: PMC11057246 DOI: 10.3389/fnins.2024.1348434] [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: 12/02/2023] [Accepted: 01/12/2024] [Indexed: 05/02/2024] Open
Abstract
Flexible high-density microelectrode arrays (HDMEAs) are emerging as a key component in closed-loop brain-machine interfaces (BMIs), providing high-resolution functionality for recording, stimulation, or both. The flexibility of these arrays provides advantages over rigid ones, such as reduced mismatch between interface and tissue, resilience to micromotion, and sustained long-term performance. This review summarizes the recent developments and applications of flexible HDMEAs in closed-loop BMI systems. It delves into the various challenges encountered in the development of ideal flexible HDMEAs for closed-loop BMI systems and highlights the latest methodologies and breakthroughs to address these challenges. These insights could be instrumental in guiding the creation of future generations of flexible HDMEAs, specifically tailored for use in closed-loop BMIs. The review thoroughly explores both the current state and prospects of these advanced arrays, emphasizing their potential in enhancing BMI technology.
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Affiliation(s)
- Xiang Liu
- Neuroscience Program, Department of Physiology, Michigan State University, East Lansing, MI, United States
- Institute for Quantitative Health Science and Engineering (IQ), East Lansing, MI, United States
| | - Yan Gong
- Institute for Quantitative Health Science and Engineering (IQ), East Lansing, MI, United States
- Department of Electrical and Computer Engineering, Michigan State University, East Lansing, MI, United States
| | - Zebin Jiang
- Institute for Quantitative Health Science and Engineering (IQ), East Lansing, MI, United States
- Department of Electrical and Computer Engineering, Michigan State University, East Lansing, MI, United States
| | - Trevor Stevens
- Department of Electrical and Computer Engineering, Michigan State University, East Lansing, MI, United States
| | - Wen Li
- Neuroscience Program, Department of Physiology, Michigan State University, East Lansing, MI, United States
- Institute for Quantitative Health Science and Engineering (IQ), East Lansing, MI, United States
- Department of Electrical and Computer Engineering, Michigan State University, East Lansing, MI, United States
- Department of Biomedical Engineering, Michigan State University, East Lansing, MI, United States
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3
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Seo HW, Cha S, Jeong Y, Ahn J, Lee KJ, Kim S, Goo YS. Focal stimulation of retinal ganglion cells using subretinal 3D microelectrodes with peripheral electrodes of opposite current. Biomed Eng Lett 2024; 14:355-365. [PMID: 38374901 PMCID: PMC10874361 DOI: 10.1007/s13534-023-00342-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2023] [Revised: 10/10/2023] [Accepted: 12/07/2023] [Indexed: 02/21/2024] Open
Abstract
Subretinal prostheses have been developed to stimulate survived retinal ganglion cells (RGCs), indirectly following the physiological visual pathways. However, current spreading from the prosthesis electrode causes the activation of unintended RGCs, thereby limiting the spatial resolution of artificial vision. This study proposes a strategy for focal stimulation of RGCs using a subretinal electrode array, in which six hexagonally arranged peripheral electrodes surround a stimulating electrode. RGCs in an in-vitro condition were subretinally stimulated using a fabricated electrode array coated with iridium oxide, following the three different stimulation configurations (with no peripheral, six electrodes of opposite current, and six ground). In-vitro experiments showed that the stimulation with six electrodes of opposite current was most effective in controlling RGC responses with a high spatial resolution. The results suggest that the effective utilization of return electrodes, such as by applying an opposite current to them, could help reduce current spreading beyond the local area targeted for stimulation and elicit RGC responses only in the vicinity of the stimulating electrode. Supplementary Information The online version contains supplementary material available at 10.1007/s13534-023-00342-3.
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Affiliation(s)
- Hee Won Seo
- Department of Robotics and Mechatronics Engineering, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu, Republic of Korea
| | - Seongkwang Cha
- Department of Physiology, Chungbuk National University School of Medicine, Cheongju, Republic of Korea
| | - Yurim Jeong
- Department of Physiology, Chungbuk National University School of Medicine, Cheongju, Republic of Korea
| | - Jungryul Ahn
- Department of Physiology, Chungbuk National University School of Medicine, Cheongju, Republic of Korea
| | - Kyeong Jae Lee
- Department of Robotics and Mechatronics Engineering, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu, Republic of Korea
| | - Sohee Kim
- Department of Robotics and Mechatronics Engineering, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu, Republic of Korea
| | - Yong Sook Goo
- Department of Physiology, Chungbuk National University School of Medicine, Cheongju, Republic of Korea
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4
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Zhang K, Liu Y, Song Y, Xu S, Yang Y, Jiang L, Sun S, Luo J, Wu Y, Cai X. Exploring retinal ganglion cells encoding to multi-modal stimulation using 3D microelectrodes arrays. Front Bioeng Biotechnol 2023; 11:1245082. [PMID: 37600306 PMCID: PMC10434521 DOI: 10.3389/fbioe.2023.1245082] [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: 06/23/2023] [Accepted: 07/21/2023] [Indexed: 08/22/2023] Open
Abstract
Microelectrode arrays (MEA) are extensively utilized in encoding studies of retinal ganglion cells (RGCs) due to their capacity for simultaneous recording of neural activity across multiple channels. However, conventional planar MEAs face limitations in studying RGCs due to poor coupling between electrodes and RGCs, resulting in low signal-to-noise ratio (SNR) and limited recording sensitivity. To overcome these challenges, we employed photolithography, electroplating, and other processes to fabricate a 3D MEA based on the planar MEA platform. The 3D MEA exhibited several improvements compared to planar MEA, including lower impedance (8.73 ± 1.66 kΩ) and phase delay (-15.11° ± 1.27°), as well as higher charge storage capacity (CSC = 10.16 ± 0.81 mC/cm2), cathodic charge storage capacity (CSCc = 7.10 ± 0.55 mC/cm2), and SNR (SNR = 8.91 ± 0.57). Leveraging the advanced 3D MEA, we investigated the encoding characteristics of RGCs under multi-modal stimulation. Optical, electrical, and chemical stimulation were applied as sensory inputs, and distinct response patterns and response times of RGCs were detected, as well as variations in rate encoding and temporal encoding. Specifically, electrical stimulation elicited more effective RGC firing, while optical stimulation enhanced RGC synchrony. These findings hold promise for advancing the field of neural encoding.
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Affiliation(s)
- Kui Zhang
- State Key Laboratory of Transducer Technology, Aerospace Information Research Institute, Chinese Academy of Sciences, Beijing, China
- School of Electronic, Electrical and Communication Engineering, University of Chinese Academy of Sciences, Beijing, China
| | - Yaoyao Liu
- State Key Laboratory of Transducer Technology, Aerospace Information Research Institute, Chinese Academy of Sciences, Beijing, China
- School of Electronic, Electrical and Communication Engineering, University of Chinese Academy of Sciences, Beijing, China
| | - Yilin Song
- State Key Laboratory of Transducer Technology, Aerospace Information Research Institute, Chinese Academy of Sciences, Beijing, China
- School of Electronic, Electrical and Communication Engineering, University of Chinese Academy of Sciences, Beijing, China
| | - Shihong Xu
- State Key Laboratory of Transducer Technology, Aerospace Information Research Institute, Chinese Academy of Sciences, Beijing, China
- School of Electronic, Electrical and Communication Engineering, University of Chinese Academy of Sciences, Beijing, China
| | - Yan Yang
- State Key Laboratory of Transducer Technology, Aerospace Information Research Institute, Chinese Academy of Sciences, Beijing, China
- School of Electronic, Electrical and Communication Engineering, University of Chinese Academy of Sciences, Beijing, China
| | - Longhui Jiang
- State Key Laboratory of Transducer Technology, Aerospace Information Research Institute, Chinese Academy of Sciences, Beijing, China
- School of Electronic, Electrical and Communication Engineering, University of Chinese Academy of Sciences, Beijing, China
| | - Shutong Sun
- State Key Laboratory of Transducer Technology, Aerospace Information Research Institute, Chinese Academy of Sciences, Beijing, China
- School of Electronic, Electrical and Communication Engineering, University of Chinese Academy of Sciences, Beijing, China
| | - Jinping Luo
- State Key Laboratory of Transducer Technology, Aerospace Information Research Institute, Chinese Academy of Sciences, Beijing, China
- School of Electronic, Electrical and Communication Engineering, University of Chinese Academy of Sciences, Beijing, China
| | - Yirong Wu
- State Key Laboratory of Transducer Technology, Aerospace Information Research Institute, Chinese Academy of Sciences, Beijing, China
- School of Electronic, Electrical and Communication Engineering, University of Chinese Academy of Sciences, Beijing, China
| | - Xinxia Cai
- State Key Laboratory of Transducer Technology, Aerospace Information Research Institute, Chinese Academy of Sciences, Beijing, China
- School of Electronic, Electrical and Communication Engineering, University of Chinese Academy of Sciences, Beijing, China
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Bhuckory M, Wang BY, Chen ZC, Shin A, Pham-Howard D, Shah S, Monkongpitukkul N, Galambos L, Kamins T, Mathieson K, Palanker D. 3D electronic implants in subretinal space: long-term follow-up in rodents. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.07.25.550561. [PMID: 37546971 PMCID: PMC10402070 DOI: 10.1101/2023.07.25.550561] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/08/2023]
Abstract
Photovoltaic subretinal prosthesis (PRIMA) enables restoration of sight via electrical stimulation of the interneurons in degenerated retina, with resolution limited by the 100 μm pixel size. Since decreasing the pixel size below 75 μm in the current bipolar geometry is impossible, we explore the possibility of using smaller pixels based on a novel 3-dimensional honeycomb-shaped design. We assessed the long-term biocompatibility and stability of these arrays in rats by investigating the anatomical integration of the retina with flat and 3D implants and response to electrical stimulation over lifetime - up to 9 months post-implantation in aged rats. With both flat and 3D implants, VEP amplitude decreased after the day of implantation by more than 3-fold, and gradually recovered over about 3 months. With 25 µm high honeycomb walls, the majority of bipolar cells migrate into the wells, while amacrine and ganglion cells remain above the cavities, which is essential for selective network-mediated stimulation of the second-order neurons. Retinal thickness and full-field stimulation threshold with 40 µm-wide honeycomb pixels were comparable to those with planar devices - 0.05 mW/mm2 with 10ms pulses. However, fewer cells from the inner nuclear layer migrated into the 20 µm-wide wells, and stimulation threshold increased over 5 months, before stabilizing at about 0.08 mW/mm2. Such threshold is significantly lower than 1.8 mW/mm2 with a previous design of flat bipolar pixels, confirming the promise of the 3D honeycomb-based approach to high resolution subretinal prosthesis.
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Affiliation(s)
- Mohajeet Bhuckory
- Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA, USA
- Department of Ophthalmology, Stanford University, Stanford, CA, USA
| | - Bing-Yi Wang
- Department of Physics, Stanford University, Stanford, CA, USA
| | - Zhijie Charles Chen
- Department of Electrical Engineering, Stanford University, Stanford, CA, USA
| | - Andrew Shin
- Department of Material Science, Stanford University, Stanford, CA, USA
| | - Davis Pham-Howard
- Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA, USA
- Department of Ophthalmology, Stanford University, Stanford, CA, USA
| | - Sarthak Shah
- Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA, USA
| | - Nicharee Monkongpitukkul
- Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA, USA
- Department of Ophthalmology, Stanford University, Stanford, CA, USA
| | - Ludwig Galambos
- Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA, USA
| | - Theodore Kamins
- Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA, USA
- Department of Electrical Engineering, Stanford University, Stanford, CA, USA
| | - Keith Mathieson
- Department of Physics, Institute of Photonics, University of Strathclyde, Glasgow, Scotland, UK
| | - Daniel Palanker
- Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA, USA
- Department of Ophthalmology, Stanford University, Stanford, CA, USA
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6
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Wu KY, Mina M, Sahyoun JY, Kalevar A, Tran SD. Retinal Prostheses: Engineering and Clinical Perspectives for Vision Restoration. SENSORS (BASEL, SWITZERLAND) 2023; 23:5782. [PMID: 37447632 PMCID: PMC10347280 DOI: 10.3390/s23135782] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2023] [Revised: 06/04/2023] [Accepted: 06/19/2023] [Indexed: 07/15/2023]
Abstract
A retinal prosthesis, also known as a bionic eye, is a device that can be implanted to partially restore vision in patients with retinal diseases that have resulted in the loss of photoreceptors (e.g., age-related macular degeneration and retinitis pigmentosa). Recently, there have been major breakthroughs in retinal prosthesis technology, with the creation of numerous types of implants, including epiretinal, subretinal, and suprachoroidal sensors. These devices can stimulate the remaining cells in the retina with electric signals to create a visual sensation. A literature review of the pre-clinical and clinical studies published between 2017 and 2023 is conducted. This narrative review delves into the retinal anatomy, physiology, pathology, and principles underlying electronic retinal prostheses. Engineering aspects are explored, including electrode-retina alignment, electrode size and material, charge density, resolution limits, spatial selectivity, and bidirectional closed-loop systems. This article also discusses clinical aspects, focusing on safety, adverse events, visual function, outcomes, and the importance of rehabilitation programs. Moreover, there is ongoing debate over whether implantable retinal devices still offer a promising approach for the treatment of retinal diseases, considering the recent emergence of cell-based and gene-based therapies as well as optogenetics. This review compares retinal prostheses with these alternative therapies, providing a balanced perspective on their advantages and limitations. The recent advancements in retinal prosthesis technology are also outlined, emphasizing progress in engineering and the outlook of retinal prostheses. While acknowledging the challenges and complexities of the technology, this article highlights the significant potential of retinal prostheses for vision restoration in individuals with retinal diseases and calls for continued research and development to refine and enhance their performance, ultimately improving patient outcomes and quality of life.
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Affiliation(s)
- Kevin Y. Wu
- Department of Surgery, Division of Ophthalmology, University of Sherbrooke, Sherbrooke, QC J1G 2E8, Canada; (K.Y.W.)
| | - Mina Mina
- Department of Mechanical and Manufacturing Engineering, University of Calgary, Calgary, AB T2N 1N4, Canada
| | - Jean-Yves Sahyoun
- Faculty of Medicine, University of Montreal, Montreal, QC H3T 1J4, Canada
| | - Ananda Kalevar
- Department of Surgery, Division of Ophthalmology, University of Sherbrooke, Sherbrooke, QC J1G 2E8, Canada; (K.Y.W.)
| | - Simon D. Tran
- Faculty of Dental Medicine and Oral Health Sciences, McGill University, Montreal, QC H3A 1G1, Canada
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Steins H, Mierzejewski M, Brauns L, Stumpf A, Kohler A, Heusel G, Corna A, Herrmann T, Jones PD, Zeck G, von Metzen R, Stieglitz T. A flexible protruding microelectrode array for neural interfacing in bioelectronic medicine. MICROSYSTEMS & NANOENGINEERING 2022; 8:131. [PMID: 36568135 PMCID: PMC9772315 DOI: 10.1038/s41378-022-00466-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2022] [Revised: 06/23/2022] [Accepted: 07/07/2022] [Indexed: 05/31/2023]
Abstract
Recording neural signals from delicate autonomic nerves is a challenging task that requires the development of a low-invasive neural interface with highly selective, micrometer-sized electrodes. This paper reports on the development of a three-dimensional (3D) protruding thin-film microelectrode array (MEA), which is intended to be used for recording low-amplitude neural signals from pelvic nervous structures by penetrating the nerves transversely to reduce the distance to the axons. Cylindrical gold pillars (Ø 20 or 50 µm, ~60 µm height) were fabricated on a micromachined polyimide substrate in an electroplating process. Their sidewalls were insulated with parylene C, and their tips were optionally modified by wet etching and/or the application of a titanium nitride (TiN) coating. The microelectrodes modified by these combined techniques exhibited low impedances (~7 kΩ at 1 kHz for Ø 50 µm microelectrode with the exposed surface area of ~5000 µm²) and low intrinsic noise levels. Their functionalities were evaluated in an ex vivo pilot study with mouse retinae, in which spontaneous neuronal spikes were recorded with amplitudes of up to 66 µV. This novel process strategy for fabricating flexible, 3D neural interfaces with low-impedance microelectrodes has the potential to selectively record neural signals from not only delicate structures such as retinal cells but also autonomic nerves with improved signal quality to study neural circuits and develop stimulation strategies in bioelectronic medicine, e.g., for the control of vital digestive functions.
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Affiliation(s)
- Helen Steins
- NMI Natural and Medical Sciences Institute at the University of Tübingen, Reutlingen, Germany
- Laboratory for Biomedical Microtechnology, Department of Microsystems Engineering, University of Freiburg, Freiburg, Germany
| | - Michael Mierzejewski
- NMI Natural and Medical Sciences Institute at the University of Tübingen, Reutlingen, Germany
| | - Lisa Brauns
- NMI Natural and Medical Sciences Institute at the University of Tübingen, Reutlingen, Germany
| | - Angelika Stumpf
- NMI Natural and Medical Sciences Institute at the University of Tübingen, Reutlingen, Germany
| | - Alina Kohler
- NMI Natural and Medical Sciences Institute at the University of Tübingen, Reutlingen, Germany
| | - Gerhard Heusel
- NMI Natural and Medical Sciences Institute at the University of Tübingen, Reutlingen, Germany
| | - Andrea Corna
- NMI Natural and Medical Sciences Institute at the University of Tübingen, Reutlingen, Germany
- Institute of Biomedical Electronics, TU Wien, Vienna, Austria
| | - Thoralf Herrmann
- NMI Natural and Medical Sciences Institute at the University of Tübingen, Reutlingen, Germany
| | - Peter D. Jones
- NMI Natural and Medical Sciences Institute at the University of Tübingen, Reutlingen, Germany
| | - Günther Zeck
- NMI Natural and Medical Sciences Institute at the University of Tübingen, Reutlingen, Germany
- Institute of Biomedical Electronics, TU Wien, Vienna, Austria
| | - Rene von Metzen
- NMI Natural and Medical Sciences Institute at the University of Tübingen, Reutlingen, Germany
| | - Thomas Stieglitz
- Laboratory for Biomedical Microtechnology, Department of Microsystems Engineering, University of Freiburg, Freiburg, Germany
- Bernstein Center Freiburg, University of Freiburg, Freiburg, Germany
- BrainLinks-BrainTools, University of Freiburg, Freiburg, Germany
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Vu QA, Seo HW, Choi KE, Kim N, Kang YN, Lee J, Park SH, Kim JT, Kim S, Kim SW. Structural changes in the retina after implantation of subretinal three-dimensional implants in mini pigs. Front Neurosci 2022; 16:1010445. [PMID: 36248640 PMCID: PMC9561346 DOI: 10.3389/fnins.2022.1010445] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2022] [Accepted: 09/16/2022] [Indexed: 11/30/2022] Open
Abstract
The retinal structural changes after subretinal implantation of three-dimensional (3D) microelectrodes were investigated in a mini pig. Three types of electrode were implanted into the subretinal spaces of nine mini pigs: 75-μm-high 3D electrodes on a 200-μm-thick right-angled polydimethylsiloxane (PDMS) substrate (group 1); a 140-μm-thick sloped PDMS substrate without electrodes (group 2); and a 140-μm-thick sloped PDMS substrate with 20-μm-high 3D electrodes (group 3). One mini pig was used as a control. Spectral domain–optical coherence tomography (SD–OCT) images were obtained at baseline and 2, 6, and 12 weeks post-surgery. Retinal specimens were immunostained using a tissue-clearing method 3 months post-implantation. The 75-μm-high 3D electrodes progressively penetrated the inner nuclear layer (INL) and touched the inner plexiform layer (IPL) 2 weeks post-surgery. At 6 weeks post-operatively, the electrodes were in contact with the nerve-fiber layer, accompanied by a severe fibrous reaction. In the other groups, the implants remained in place without subretinal migration. Immunostaining showed that retinal ganglion and bipolar cells were preserved without fibrosis over the retinal implants in groups 2 and 3 during the 12-week implantation period. In summary, SD–OCT and immunohistology results showed differences in the extent of reactions, such as fibrosis over the implants and penetration of the electrodes into the inner retinal layer depending on different types of electrodes. A sloped substrate performed better than a right-angled substrate in terms of retinal preservation over the implanted electrodes. The 20-μm-high electrodes showed better structural compatibility than the 75-μm-high 3D electrodes. There was no significant difference between the results of sloped implants without electrodes and 20-μm-high 3D electrodes, indicating that the latter had no adverse effects on retinal tissue.
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Affiliation(s)
- Que Anh Vu
- Department of Ophthalmology, Korea University School of Medicine, Seoul, South Korea
- Department of Ophthalmology, Hanoi Medical University, Hanoi, Vietnam
| | - Hee Won Seo
- Department of Robotics and Mechatronics Engineering, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu, South Korea
| | - Kwang-Eon Choi
- Department of Ophthalmology, Korea University School of Medicine, Seoul, South Korea
| | - Namju Kim
- Department of Robotics and Mechatronics Engineering, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu, South Korea
| | - Yoo Na Kang
- Department of Medical Assistant Robot, Korea Institute of Machinery and Materials (KIMM), Daegu, South Korea
| | - Jaemeun Lee
- R&D Center for Advanced Pharmaceuticals and Evaluation, Korea Institute of Toxicology, Daejeon, South Korea
| | - Sun-Hyun Park
- R&D Center for Advanced Pharmaceuticals and Evaluation, Korea Institute of Toxicology, Daejeon, South Korea
| | - Jee Taek Kim
- Department of Ophthalmology, Chung-Ang University College of Medicine, Seoul, South Korea
| | - Sohee Kim
- Department of Robotics and Mechatronics Engineering, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu, South Korea
- *Correspondence: Sohee Kim,
| | - Seong-Woo Kim
- Department of Ophthalmology, Korea University School of Medicine, Seoul, South Korea
- Seong-Woo Kim,
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9
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Kim S, Roh H, Im M. Artificial Visual Information Produced by Retinal Prostheses. Front Cell Neurosci 2022; 16:911754. [PMID: 35734216 PMCID: PMC9208577 DOI: 10.3389/fncel.2022.911754] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2022] [Accepted: 05/18/2022] [Indexed: 11/18/2022] Open
Abstract
Numerous retinal prosthetic systems have demonstrated somewhat useful vision can be restored to individuals who had lost their sight due to outer retinal degenerative diseases. Earlier prosthetic studies have mostly focused on the confinement of electrical stimulation for improved spatial resolution and/or the biased stimulation of specific retinal ganglion cell (RGC) types for selective activation of retinal ON/OFF pathway for enhanced visual percepts. To better replicate normal vision, it would be also crucial to consider information transmission by spiking activities arising in the RGC population since an incredible amount of visual information is transferred from the eye to the brain. In previous studies, however, it has not been well explored how much artificial visual information is created in response to electrical stimuli delivered by microelectrodes. In the present work, we discuss the importance of the neural information for high-quality artificial vision. First, we summarize the previous literatures which have computed information transmission rates from spiking activities of RGCs in response to visual stimuli. Second, we exemplify a couple of studies which computed the neural information from electrically evoked responses. Third, we briefly introduce how information rates can be computed in the representative two ways – direct method and reconstruction method. Fourth, we introduce in silico approaches modeling artificial retinal neural networks to explore the relationship between amount of information and the spiking patterns. Lastly, we conclude our review with clinical implications to emphasize the necessity of considering visual information transmission for further improvement of retinal prosthetics.
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Affiliation(s)
- Sein Kim
- Brain Science Institute, Korea Institute of Science and Technology, Seoul, South Korea
| | - Hyeonhee Roh
- Brain Science Institute, Korea Institute of Science and Technology, Seoul, South Korea
- School of Electrical Engineering, College of Engineering, Korea University, Seoul, South Korea
| | - Maesoon Im
- Brain Science Institute, Korea Institute of Science and Technology, Seoul, South Korea
- Division of Bio-Medical Science & Technology, KIST School, University of Science and Technology, Seoul, South Korea
- *Correspondence: Maesoon Im, ,
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10
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Vėbraitė I, Hanein Y. Soft Devices for High-Resolution Neuro-Stimulation: The Interplay Between Low-Rigidity and Resolution. FRONTIERS IN MEDICAL TECHNOLOGY 2022; 3:675744. [PMID: 35047928 PMCID: PMC8757739 DOI: 10.3389/fmedt.2021.675744] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2021] [Accepted: 05/14/2021] [Indexed: 12/27/2022] Open
Abstract
The field of neurostimulation has evolved over the last few decades from a crude, low-resolution approach to a highly sophisticated methodology entailing the use of state-of-the-art technologies. Neurostimulation has been tested for a growing number of neurological applications, demonstrating great promise and attracting growing attention in both academia and industry. Despite tremendous progress, long-term stability of the implants, their large dimensions, their rigidity and the methods of their introduction and anchoring to sensitive neural tissue remain challenging. The purpose of this review is to provide a concise introduction to the field of high-resolution neurostimulation from a technological perspective and to focus on opportunities stemming from developments in materials sciences and engineering to reduce device rigidity while optimizing electrode small dimensions. We discuss how these factors may contribute to smaller, lighter, softer and higher electrode density devices.
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Affiliation(s)
- Ieva Vėbraitė
- School of Electrical Engineering, Tel Aviv University, Tel Aviv, Israel
| | - Yael Hanein
- School of Electrical Engineering, Tel Aviv University, Tel Aviv, Israel
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Kang JH, Jang YJ, Kim T, Lee BC, Lee SH, Im M. Electric Stimulation Elicits Heterogeneous Responses in ON but Not OFF Retinal Ganglion Cells to Transmit Rich Neural Information. IEEE Trans Neural Syst Rehabil Eng 2021; 29:300-309. [PMID: 33395394 DOI: 10.1109/tnsre.2020.3048973] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Retinal implants electrically stimulate surviving retinal neurons to restore vision in people blinded by outer retinal degeneration. Although the healthy retina is known to transmit a vast amount of visual information to the brain, it has not been studied whether prosthetic vision contains a similar amount of information. Here, we assessed the neural information transmitted by population responses arising in brisk transient (BT) and brisk sustained (BS) subtypes of ON and OFF retinal ganglion cells (RGCs) in the rabbit retina. To correlate the response heterogeneity and the information transmission, we first quantified the cell-to-cell heterogeneity by calculating the spike time tiling coefficient (STTC) across spiking patterns of RGCs in each type. Then, we computed the neural information encoded by the RGC population in a given type. In responses to light stimulation, spiking activities were more heterogeneous in OFF than ON RGCs (STTCAVG = 0.36, 0.45, 0.77 and 0.55 for OFF BT, OFF BS, ON BT, and ON BS, respectively). Interestingly, however, in responses to electric stimulation, both BT and BS subtypes of OFF RGCs showed remarkably homogeneous spiking patterns across cells (STTCAVG = 0.93 and 0.82 for BT and BS, respectively), whereas the two subtypes of ON RGCs showed slightly increased populational heterogeneity compared to light-evoked responses (STTCAVG = 0.71 and 0.63 for BT and BS, respectively). Consequently, the neural information encoded by the electrically-evoked responses of a population of 15 RGCs was substantially lower in the OFF than the ON pathway: OFF BT and BS cells transmit only ~23% and ~53% of the neural information transmitted by their ON counterparts. Together with previously-reported natural spiking activities in ON RGCs, the higher neural information may make ON responses more recognizable, eliciting the biased percepts of bright phosphenes.
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Editorial for the Special Issue on Micro/Nanofabrication for Retinal Implants. MICROMACHINES 2020; 11:mi11111005. [PMID: 33202623 PMCID: PMC7696498 DOI: 10.3390/mi11111005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 11/12/2020] [Accepted: 11/13/2020] [Indexed: 11/16/2022]
Abstract
The retinal prosthetic community has witnessed tremendous technological advances during the last two decades since the emergence of pioneering work [...].
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