1
|
Xu C, Lu G, Kang H, Humayun MS, Zhou Q. Design and Simulation of a Ring Transducer Array for Ultrasound Retinal Stimulation. MICROMACHINES 2022; 13:1536. [PMID: 36144157 PMCID: PMC9503310 DOI: 10.3390/mi13091536] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/15/2022] [Revised: 08/22/2022] [Accepted: 09/10/2022] [Indexed: 06/16/2023]
Abstract
Argus II retinal prosthesis is the US Food and Drug Administration (FDA) approved medical device intended to restore sight to a patient's blind secondary to retinal degeneration (i.e., retinitis pigmentosa). However, Argus II and most reported retinal prostheses require invasive surgery to implant electrodes in the eye. Recent studies have shown that focused ultrasound can be developed into a non-invasive retinal prosthesis technology. Ultrasound energy focused on retinal neurons can trigger the activities of retinal neurons with high spatial-temporal resolution. This paper introduces a novel design and simulation of a ring array transducer that could be used as non-invasive ultrasonic retinal stimulation. The array transducer is designed in the shape of a racing ring with a hemisphere surface that mimics a contact lens to acoustically couple with the eye via the tear film and directs the ultrasound to avoid the high acoustic absorption from the crystalline lens. We will describe the design methods and simulation of the two-dimensional pattern stimulation. Finally, compared with other existing retinal prostheses, we show that the ultrasound ring array is practical and safe and could be potentially used as a non-invasive retinal prosthesis.
Collapse
Affiliation(s)
- Chenlin Xu
- Department of Biomedical Engineering, University of Southern California, Los Angeles, CA 90089, USA
| | - Gengxi Lu
- Department of Biomedical Engineering, University of Southern California, Los Angeles, CA 90089, USA
- USC Roski Eye Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA
| | - Haochen Kang
- Department of Biomedical Engineering, University of Southern California, Los Angeles, CA 90089, USA
| | - Mark S. Humayun
- Department of Biomedical Engineering, University of Southern California, Los Angeles, CA 90089, USA
- USC Roski Eye Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA
- USC Ginsburg Institute for Biomedical Therapeutics, University of Southern California, Los Angeles, CA 90033, USA
| | - Qifa Zhou
- Department of Biomedical Engineering, University of Southern California, Los Angeles, CA 90089, USA
- USC Roski Eye Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA
- USC Ginsburg Institute for Biomedical Therapeutics, University of Southern California, Los Angeles, CA 90033, USA
| |
Collapse
|
2
|
Liu W, Liu S, Li P, Yao K. Retinitis Pigmentosa: Progress in Molecular Pathology and Biotherapeutical Strategies. Int J Mol Sci 2022; 23:ijms23094883. [PMID: 35563274 PMCID: PMC9101511 DOI: 10.3390/ijms23094883] [Citation(s) in RCA: 37] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Revised: 04/25/2022] [Accepted: 04/26/2022] [Indexed: 12/13/2022] Open
Abstract
Retinitis pigmentosa (RP) is genetically heterogeneous retinopathy caused by photoreceptor cell death and retinal pigment epithelial atrophy that eventually results in blindness in bilateral eyes. Various photoreceptor cell death types and pathological phenotypic changes that have been disclosed in RP demand in-depth research of its pathogenic mechanism that may account for inter-patient heterogeneous responses to mainstream drug treatment. As the primary method for studying the genetic characteristics of RP, molecular biology has been widely used in disease diagnosis and clinical trials. Current technology iterations, such as gene therapy, stem cell therapy, and optogenetics, are advancing towards precise diagnosis and clinical applications. Specifically, technologies, such as effective delivery vectors, CRISPR/Cas9 technology, and iPSC-based cell transplantation, hasten the pace of personalized precision medicine in RP. The combination of conventional therapy and state-of-the-art medication is promising in revolutionizing RP treatment strategies. This article provides an overview of the latest research on the pathogenesis, diagnosis, and treatment of retinitis pigmentosa, aiming for a convenient reference of what has been achieved so far.
Collapse
|
3
|
Khan ZM, Wilts E, Vlaisavljevich E, Long TE, Verbridge SS. Electroresponsive Hydrogels for Therapeutic Applications in the Brain. Macromol Biosci 2021; 22:e2100355. [PMID: 34800348 DOI: 10.1002/mabi.202100355] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2021] [Revised: 10/29/2021] [Indexed: 12/22/2022]
Abstract
Electroresponsive hydrogels possess a conducting material component and respond to electric stimulation through reversible absorption and expulsion of water. The high level of hydration, soft elastomeric compliance, biocompatibility, and enhanced electrochemical properties render these hydrogels suitable for implantation in the brain to enhance the transmission of neural electric signals and ion transport. This review provides an overview of critical electroresponsive hydrogel properties for augmenting electric stimulation in the brain. A background on electric stimulation in the brain through electroresponsive hydrogels is provided. Common conducting materials and general techniques to integrate them into hydrogels are briefly discussed. This review focuses on and summarizes advances in electric stimulation of electroconductive hydrogels for therapeutic applications in the brain, such as for controlling delivery of drugs, directing neural stem cell differentiation and neurogenesis, improving neural biosensor capabilities, and enhancing neural electrode-tissue interfaces. The key challenges in each of these applications are discussed and recommendations for future research are also provided.
Collapse
Affiliation(s)
- Zerin M Khan
- Virginia Tech - Wake Forest University School of Biomedical Engineering and Sciences, Virginia Tech, Blacksburg, VA, 24061, USA
| | - Emily Wilts
- Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, British Columbia, V6T 1Z3, Canada
| | - Eli Vlaisavljevich
- Virginia Tech - Wake Forest University School of Biomedical Engineering and Sciences, Virginia Tech, Blacksburg, VA, 24061, USA
| | - Timothy E Long
- Biodesign Center for Sustainable Macromolecular Materials and Manufacturing, Arizona State University, Tempe, AZ, 85287, USA
| | - Scott S Verbridge
- Virginia Tech - Wake Forest University School of Biomedical Engineering and Sciences, Virginia Tech, Blacksburg, VA, 24061, USA
| |
Collapse
|
4
|
Abbasi B, Rizzo JF. Advances in Neuroscience, Not Devices, Will Determine the Effectiveness of Visual Prostheses. Semin Ophthalmol 2021; 36:168-175. [PMID: 33734937 DOI: 10.1080/08820538.2021.1887902] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Background: Innovations in engineering and neuroscience have enabled the development of sophisticated visual prosthetic devices. In clinical trials, these devices have provided visual acuities as high as 20/460, enabled coarse navigation, and even allowed for reading of short words. However, long-term commercial viability arguably rests on attaining even better vision and more definitive improvements in tasks of daily living and quality of life. Purpose: Here we review technological and biological obstacles in the implementation of visual prosthetics. Conclusions: Research in the visual prosthetic field has tackled significant technical challenges, including biocompatibility, signal spread through neural tissue, and inadvertent activation of passing axons; however, significant gaps in knowledge remain in the realm of neuroscience, including the neural code of vision and visual plasticity. We assert that further optimization of prosthetic devices alone will not provide markedly improved visual outcomes without significant advances in our understanding of neuroscience.
Collapse
Affiliation(s)
- Bardia Abbasi
- Neuro-Ophthalmology Service, Department of Ophthalmology, Massachusetts Eye and Ear and Harvard Medical School, Boston, MA, USA
| | - Joseph F Rizzo
- Neuro-Ophthalmology Service, Department of Ophthalmology, Massachusetts Eye and Ear and Harvard Medical School, Boston, MA, USA
| |
Collapse
|
5
|
Lu G, Qian X, Castillo J, Li R, Jiang L, Lu H, Kirk Shung K, Humayun MS, Thomas BB, Zhou Q. Transcranial Focused Ultrasound for Noninvasive Neuromodulation of the Visual Cortex. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2021; 68:21-28. [PMID: 32746196 PMCID: PMC8153235 DOI: 10.1109/tuffc.2020.3005670] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
Currently, blindness cannot be cured and patients' living quality can be compromised severely. Ultrasonic (US) neuromodulation is a promising technology for the development of noninvasive cortical visual prosthesis. We investigated the feasibility of transcranial focused ultrasound (tFUS) for noninvasive stimulation of the visual cortex (VC) to develop improved visual prosthesis. tFUS was used to successfully evoke neural activities in the VC of both normal and retinal degenerate (RD) blind rats. Our results showed that blind rats showed more robust responses to ultrasound stimulation when compared with normal rats. ( , two-sample t-test). Three different types of ultrasound waveforms were used in the three experimental groups. Different types of cortical activities were observed when different US waveforms were used. In all rats, when stimulated with continuous ultrasound waves, only short-duration responses were observed at "US on and off" time points. In comparison, pulsed waves (PWs) evoked longer low-frequency responses. Testing different parameters of PWs showed that a pulse repetition frequency higher than 100 Hz is required to obtain the low-frequency responses. Based on the observed cortical activities, we inferred that acoustic radiation force (ARF) is the predominant physical mechanism of ultrasound neuromodulation.
Collapse
|
6
|
Mishra A, Mohan KV, Nagarajan P, Iyer S, Kesarwani A, Nath M, Moksha L, Bhattacharjee J, Das B, Jain K, Sahu P, Sinha P, Velapandian T, Upadhyay P. Peripheral blood-derived monocytes show neuronal properties and integration in immune-deficient rd1 mouse model upon phenotypic differentiation and induction with retinal growth factors. Stem Cell Res Ther 2020; 11:412. [PMID: 32967734 PMCID: PMC7510317 DOI: 10.1186/s13287-020-01925-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Revised: 08/17/2020] [Accepted: 09/04/2020] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Cell therapy is one of the most promising therapeutic interventions for retinitis pigmentosa. In the current study, we aimed to assess if peripheral blood-derived monocytes which are highly abundant and accessible could be utilized as a potential candidate for phenotypic differentiation into neuron-like cells. METHODS The peripheral blood-derived monocytes were reconditioned phenotypically using extrinsic growth factors to induce pluripotency and proliferation. The reconditioned monocytes (RM) were further incubated with a cocktail of growth factors involved in retinal development and growth to induce retinal neuron-like properties. These cells, termed as retinal neuron-like cells (RNLCs) were characterized for their morphological, molecular and functional behaviour in vitro and in vivo. RESULTS The monocytes de-differentiated in vitro and acquired pluripotency with the expression of prominent stem cell markers. Treatment of RM with retinal growth factors led to an upregulation of neuronal and retinal lineage markers and downregulation of myeloid markers. These cells show morphological alterations resembling retinal neuron-like cells and expressed photoreceptor (PR) markers. The induced RNLCs also exhibited relative membrane potential change upon light exposure suggesting that they have gained some neuronal characteristics. Further studies showed that RNLCs could also integrate in an immune-deficient retinitis pigmentosa mouse model NOD.SCID-rd1 upon sub-retinal transplantation. The RNLCs engrafted in the inner nuclear layer (INL) and ganglion cell layer (GCL) of the RP afflicted retina. Mice transplanted with RNLCs showed improvement in depth perception, exploratory behaviour and the optokinetic response. CONCLUSIONS This proof-of-concept study demonstrates that reconditioned monocytes can be induced to acquire retinal neuron-like properties through differentiation using a defined growth media and can be a potential candidate for cell therapy-based interventions and disease modelling for ocular diseases.
Collapse
Affiliation(s)
- Alaknanda Mishra
- National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi, 110067, India
| | - K Varsha Mohan
- National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi, 110067, India
| | - Perumal Nagarajan
- National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi, 110067, India
| | - Srikanth Iyer
- National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi, 110067, India
| | - Ashwani Kesarwani
- National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi, 110067, India
| | - Madhu Nath
- Department of Ocular Pharmacology, Dr. Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, 110029, India
| | - Laxmi Moksha
- Department of Ocular Pharmacology, Dr. Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, 110029, India
| | | | - Barun Das
- National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi, 110067, India
| | - Kshama Jain
- National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi, 110067, India
| | - Parul Sahu
- National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi, 110067, India
| | - Prakriti Sinha
- National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi, 110067, India
| | - T Velapandian
- Department of Ocular Pharmacology, Dr. Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, 110029, India
| | - Pramod Upadhyay
- National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi, 110067, India.
| |
Collapse
|
7
|
Chen J, Poulaki V, Kim SJ, Eldred WD, Kane S, Gingerich M, Shire DB, Jensen R, DeWalt G, Kaplan HJ, Rizzo JF. Implantation and Extraction of Penetrating Electrode Arrays in Minipig Retinas. Transl Vis Sci Technol 2020; 9:19. [PMID: 32821491 PMCID: PMC7401973 DOI: 10.1167/tvst.9.5.19] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2018] [Accepted: 12/31/2019] [Indexed: 12/12/2022] Open
Abstract
Purpose This work was motivated by the goals of demonstrating methods to fabricate and implant large numbers of penetrating arrays into the retina and the feasibility of extraction. Methods Arrays of inactive, three-dimensional (3D) SU-8 structures were microfabricated onto 13-µm polyimide substrates. Standard vitreoretinal surgical techniques were used with an ab externo approach for subretinal implantation of arrays in 12 mini-pigs. In the first three surgeries, different post-geometries were explored, while a preferred design (128-µm tall, 30-µm diameter, 200-µm spacing) was used for the remaining nine implantations. Two arrays were extracted. Funduscopy, optical coherence tomography (OCT) and immunohistochemistry of the retinae were performed. The unoperated eyes and tissue far from implantation served as controls. A thirteenth pig was implanted with a planar array. Results Ten implant surgeries had no significant complication, and two arrays were successfully extracted. One retinal tear occurred after implantation due to too long posts in an early surgery. In “successful” cases, OCT showed close apposition of the arrays to the retina and integration of the posts, the tops of which were positioned at the junction of the inner plexiform and ganglion cells, without significant gliosis. Conclusions These results provide a proof-of-concept that relatively large numbers of 3D posts can be implanted into, and extracted from, the retina of mini-pigs. Our surgical numbers were relatively small, especially for the extractions, and our conclusions must be viewed with that limitation. Our methods are applicable for human surgeries. Translational Relevance This study provides results of implantation and extraction of relatively large numbers of 3D posts from the retina of minipig eyes. If similar technology were used in humans, a 3D array of this type should lower perceptual thresholds, provide safer long-term stimulation, and perhaps provide better perceptual outcomes.
Collapse
Affiliation(s)
- Jinghua Chen
- Department of Ophthalmology, University of Florida, College of Medicine, Gainesville, FL, USA
| | - Vasiliki Poulaki
- Boston VA Healthcare System, Ophthalmology, Jamaica Plain, Boston, MA, USA
| | - Seong-Joon Kim
- Department of Ophthalmology, Seoul National University College of Medicine, Seoul, Korea
| | | | | | | | | | - Ralph Jensen
- Boston VA Healthcare System, Ophthalmology, Jamaica Plain, Boston, MA, USA
| | - Gloria DeWalt
- Department of Biology, Boston University, Boston, MA, USA
| | - Henry J Kaplan
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY, USA
| | - Joseph F Rizzo
- Department of Ophthalmology, Harvard Medical School and the Massachusetts Eye and Ear, Boston, MA, USA
| |
Collapse
|
8
|
Electrochemical characteristics of microelectrode designed for electrical stimulation. Biomed Eng Online 2019; 18:86. [PMID: 31370902 PMCID: PMC6676582 DOI: 10.1186/s12938-019-0704-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2019] [Accepted: 07/23/2019] [Indexed: 01/06/2023] Open
Abstract
Background Microelectrode arrays play an important role in prosthetic implants for neural signal recording or applying electrical pulses stimulation to target nerve system. Safety and long-term reliability are essential requirements for microelectrode arrays applied in electrical stimulation. In design and fabrication of the microelectrode array, soft materials are generally chosen to be the substrate for the aim of achieving better compliance with the surrounding tissue while maintaining minimal damage. By flexing of the array to the surface, the array is capable of keeping a more stable electrical contact resulting in a significantly improved signal detected. Methods In this study, we design and fabricate a flexible microelectrode array with gold as the electrode material and parylene-C as the substrate. The fabrication process of the array is presented. The in vitro electrochemical characteristics of the microelectrode are investigated by electrochemical impedance spectroscopy and cyclic voltammetry in a three-electrode electrochemical cell containing phosphate-buffered saline. Charge injection capacity measurements are carried out by multichannel systems and the CSC of the microarray is calculated. Results Electrochemical results showed that impedance decreased with frequency. The average impedance of the Au electrodes at 1 kHz was 36.54 ± 0.88 kΩ. The average phase angle at 1 kHz was − 73.52 ± 1.3°, and the CIC of the microelectrode was 22.3 µC/cm2. The results demonstrated that the microelectrode array performed as expected for neuronal signal recording or stimulation. Conclusions With parylene-C as the substrate, the microarray has good flexibility. The electrochemical characteristics’ results show that the array has the ability to resist any corrosion on metal–electrolyte interface and has good biocompatibility. This low-cost, flexible parylene-based, gold microelectrode array shows potential for use in implant neurological signal acquisition or neurostimulation applications.
Collapse
|
9
|
Jiang Q, Li G, Zhao H, Sheng W, Yue L, Su M, Weng S, Chan LLH, Zhou Q, Humayun MS, Qiu W, Zheng H. Temporal Neuromodulation of Retinal Ganglion Cells by Low-Frequency Focused Ultrasound Stimulation. IEEE Trans Neural Syst Rehabil Eng 2019; 26:969-976. [PMID: 29752231 DOI: 10.1109/tnsre.2018.2821194] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Significant progress has been made recently in treating neurological blindness using implantable visual prostheses. However, implantable medical devices are highly invasive and subject to many safety, efficacy, and cost issues. The discovery that ultrasound (US) may be useful as a noninvasive neuromodulation tool has aroused great interest in the field of acoustic retinal prostheses (ARPs). We have investigated the responsiveness of rat retinal ganglion cells (RGCs) to low-frequency focused US stimulation (LFUS) at 2.25 MHz and characterized the neurophysiological properties of US responses by performing in vitro multielectrode array recordings. The results show that LFUS can reliably activate RGCs. The US-induced responses did not correspond to the standard light responses and varied greatly among cell types. Moreover, dual-peak responses to US stimulation were observed that have not been reported previously. The temporal response properties of RGCs, including their latency, firing rate, and response type, were modulated by the acoustic intensity. These findings suggest the presence of a temporal neuromodulation effect of LFUS and potentially open a new avenue in the development of ARP.
Collapse
|
10
|
A Novel Racing Array Transducer for Noninvasive Ultrasonic Retinal Stimulation: A Simulation Study. SENSORS 2019; 19:s19081825. [PMID: 30999576 PMCID: PMC6514975 DOI: 10.3390/s19081825] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/01/2019] [Revised: 03/27/2019] [Accepted: 04/03/2019] [Indexed: 12/26/2022]
Abstract
Neurostimulation has proved to be an effective method for the restoration of visual perception lost due to retinal diseases. However, the clinically available retinal neurostimulation method is based on invasive electrodes, making it a high-cost and high-risk procedure. Recently, ultrasound has been demonstrated to be an effective way to achieve noninvasive neurostimulation. In this work, a novel racing array transducer with a contact lens shape is proposed for ultrasonic retinal stimulation. The transducer is flexible and placed outside the eyeball, similar to the application of a contact lens. Ultrasound emitted from the transducer can reach the retina without passing through the lens, thus greatly minimizing the acoustic absorption in the lens. The discretized Rayleigh–Sommerfeld method was employed for the acoustic field simulation, and patterned stimulation was achieved. A 5 MHz racing array transducer with different element numbers was simulated to optimize the array configuration. The results show that a 512-element racing array is the most appropriate configuration considering the necessary tradeoff between the element number and the stimulation resolution. The stimulation resolution at a focus of 24 mm is about 0.6 mm. The obtained results indicate that the proposed racing array design of the ultrasound transducer can improve the feasibility of an ultrasound retinal prosthesis.
Collapse
|
11
|
Yang JW, Tseng ML, Fu YM, Kang CH, Cheng YT, Kuo PH, Tzeng CK, Chiou SH, Wu CY, Chen GY. Printable Graphene Oxide Micropatterns for a Bio-Subretinal Chip. Adv Healthc Mater 2018; 7:e1800365. [PMID: 30051620 DOI: 10.1002/adhm.201800365] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2018] [Revised: 06/09/2018] [Indexed: 01/23/2023]
Abstract
Recently, implantable artificial subretinal chips using electronic components have replaced photoreceptors to serve as the most feasible treatment for retinal diseases. As such a chip that is meant to be implanted and used for very long periods, growing retinal cells on it to improve the electrical stimulation efficiency and attraction of neuronal elements remains a challenge. Here, an inkjet printing technology is employed to create graphene oxide (GO) micropatterns onto microelectrodes of a photovoltaic-powered implantable retinal chip. These GO micropatterns allow human retinal pigment epithelium (RPE) cells to specially attach and grow in each microelectrode. In addition, the cell proliferation, viability, and tight junction of RPE cells are improved during culturing. The development of a simple surface-coating technology would pave the way for the development of the first fully integrated and encapsulated retinal prostheses with biocompatible on-chip microelectrodes for long-term implantation, which could be effectively applied in retina tissue engineering and therapy.
Collapse
Affiliation(s)
- Jia-Wei Yang
- Department of Electrical and Computer Engineering; National Chiao Tung University; Hsinchu 300 Taiwan
- Institute of Biomedical Engineering; College of Electrical and Computer Engineering; National Chiao Tung University; Hsinchu 300 Taiwan
| | - Ming-Liang Tseng
- Institute of Biomedical Engineering; College of Electrical and Computer Engineering; National Chiao Tung University; Hsinchu 300 Taiwan
| | - Yu-Min Fu
- Microsystems Integration Laboratory; Department of Electronics Engineering; National Chiao Tung University; Hsinchu 300 Taiwan
| | - Che-Hao Kang
- Microsystems Integration Laboratory; Department of Electronics Engineering; National Chiao Tung University; Hsinchu 300 Taiwan
| | - Yu-Ting Cheng
- Microsystems Integration Laboratory; Department of Electronics Engineering; National Chiao Tung University; Hsinchu 300 Taiwan
| | - Po-Han Kuo
- Department of Electrical Engineering; National Chiao Tung University; Hsinchu 300 Taiwan
| | - Chi-Kuan Tzeng
- Department of Electrical Engineering; National Chiao Tung University; Hsinchu 300 Taiwan
| | - Shih-Hwa Chiou
- Institute of Pharmacology; School of Medicine; National Yang-Ming University; Taipei 112 Taiwan
- Department of Medical Research; Taipei Veterans General Hospital; Taipei 112 Taiwan
- Genomics Research Center; Academia Sinica; Taipei 115 Taiwan
| | - Chung-Yu Wu
- Department of Electrical Engineering; National Chiao Tung University; Hsinchu 300 Taiwan
| | - Guan-Yu Chen
- Institute of Biomedical Engineering; College of Electrical and Computer Engineering; National Chiao Tung University; Hsinchu 300 Taiwan
- Department of Biological Science and Technology; National Chiao Tung University; Hsinchu 300 Taiwan
- Institute of Biomedical Engineering; College of Electrical and Computer Engineering; National Chiao Tung University; Hsinchu 300 Taiwan
| |
Collapse
|
12
|
Tochitsky I, Kienzler MA, Isacoff E, Kramer RH. Restoring Vision to the Blind with Chemical Photoswitches. Chem Rev 2018; 118:10748-10773. [PMID: 29874052 DOI: 10.1021/acs.chemrev.7b00723] [Citation(s) in RCA: 89] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Degenerative retinal diseases such as retinitis pigmentosa (RP) and age-related macular degeneration (AMD) affect millions of people around the world and lead to irreversible vision loss if left untreated. A number of therapeutic strategies have been developed over the years to treat these diseases or restore vision to already blind patients. In this Review, we describe the development and translational application of light-sensitive chemical photoswitches to restore visual function to the blind retina and compare the translational potential of photoswitches with other vision-restoring therapies. This therapeutic strategy is enabled by an efficient fusion of chemical synthesis, chemical biology, and molecular biology and is broadly applicable to other biological systems. We hope this Review will be of interest to chemists as well as neuroscientists and clinicians.
Collapse
Affiliation(s)
- Ivan Tochitsky
- F.M. Kirby Neurobiology Center , Boston Children's Hospital , Boston , Massachusetts 02115 , United States.,Department of Neurobiology , Harvard Medical School , Boston , Massachusetts 02115 , United States
| | - Michael A Kienzler
- Department of Chemistry , University of Maine , Orono , Maine 04469 , United States
| | - Ehud Isacoff
- Department of Molecular and Cell Biology , University of California , Berkeley , California 94720 , United States.,Helen Wills Neuroscience Institute , University of California , Berkeley , California 94720 , United States.,Bioscience Division , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
| | - Richard H Kramer
- Department of Molecular and Cell Biology , University of California , Berkeley , California 94720 , United States.,Helen Wills Neuroscience Institute , University of California , Berkeley , California 94720 , United States
| |
Collapse
|
13
|
Dubey A, Jangir H, Pandey M, Dubey MM, Verma S, Roy M, Singh SK, Philip D, Sarkar S, Das M. An eco-friendly, low-power charge storage device from bio-tolerable nano cerium oxide electrodes for bioelectrical and biomedical applications. Biomed Phys Eng Express 2018. [DOI: 10.1088/2057-1976/aaa282] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
|
14
|
Microspheres as intraocular therapeutic tools in chronic diseases of the optic nerve and retina. Adv Drug Deliv Rev 2018; 126:127-144. [PMID: 29339146 DOI: 10.1016/j.addr.2018.01.007] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Revised: 01/04/2018] [Accepted: 01/10/2018] [Indexed: 01/09/2023]
Abstract
Pathologies affecting the optic nerve and the retina are one of the major causes of blindness. These diseases include age-related macular degeneration (AMD), diabetic retinopathy (DR) and glaucoma, among others. Also, there are genetic disorders that affect the retina causing visual impairment. The prevalence of neurodegenerative diseases of the posterior segment is increased as most of them are related with the elderly. Even with the access to different treatments, there are some challenges in managing patients suffering retinal diseases. One of them is the need for frequent interventions. Also, an unpredictable response to therapy has suggested that different pathways may be playing a role in the development of these diseases. The management of these pathologies requires the development of controlled drug delivery systems able to slow the progression of the disease without the need of frequent invasive interventions, typically related with endophthalmitis, retinal detachment, ocular hypertension, cataract, inflammation, and floaters, among other. Biodegradable microspheres are able to encapsulate low molecular weight substances and large molecules such as biotechnological products. Over the last years, a large variety of active substances has been encapsulated in microspheres with the intention of providing neuroprotection of the optic nerve and the retina. The purpose of the present review is to describe the use of microspheres in chronic neurodegenerative diseases affecting the retina and the optic nerve. The advantage of microencapsulation of low molecular weight drugs as well as therapeutic peptides and proteins to be used as neuroprotective strategy is discussed. Also, a new use of the microspheres in the development of animal models of neurodegeneration of the posterior segment is described.
Collapse
|
15
|
Wang MH, Ji BW, Gu XW, Tian HC, Kang XY, Yang B, Wang XL, Chen X, Li CY, Liu JQ. Direct electrodeposition of Graphene enhanced conductive polymer on microelectrode for biosensing application. Biosens Bioelectron 2018; 99:99-107. [DOI: 10.1016/j.bios.2017.07.030] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2017] [Revised: 07/01/2017] [Accepted: 07/11/2017] [Indexed: 11/27/2022]
|
16
|
Tuft BW, Xu L, Leigh B, Lee D, Guymon CA, Hansen MR. Photopolymerized micropatterns with high feature frequencies overcome chemorepulsive borders to direct neurite growth. J Tissue Eng Regen Med 2017; 12:e1392-e1403. [PMID: 28753740 DOI: 10.1002/term.2527] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2017] [Revised: 07/03/2017] [Accepted: 07/24/2017] [Indexed: 01/04/2023]
Abstract
Developing and regenerating neurites respond to a variety of biophysical and biochemical cues in their micro-environment to reach target cells and establish appropriate synapses. Defining the hierarchal relationship of both types of cues to direct neurite growth carries broad significance for neural development, regeneration, and, in particular, engineering of neural prostheses that improve tissue integration with native neural networks. In this work, chemorepulsive biochemical borders are established on substrates with a range of surface microfeatures to determine the potential of physical cues to overcome conflicting biochemical cues. Physical micropatterns are fabricated using photomasking techniques to spatially control photoinitiation events of the polymerization. Temporal control of the reaction allows for generation of microfeatures with the same amplitude across a range of feature frequencies or periodicities. The micropatterned substrates are then modified with repulsive chemical borders between laminin and either EphA4-Fc or tenascin C that compete with the surface microfeatures to direct neurite growth. Behaviour of neurites from spiral ganglion and trigeminal neurons is characterized at biochemical borders as cross, turn, stop, or repel events. Both the chemical borders and physical patterns significantly influence neurite pathfinding. On unpatterned surfaces, most neurites that originate on laminin are deterred by the border with tenascin C or EphA4-Fc. Importantly, substrates with frequent micropattern features overcome the influence of the chemorepulsive border to dominate neurite trajectory. Designing prosthesis interfaces with appropriate surface features may allow for spatially organized neurite outgrowth in vivo even in the presence of conflicting biochemical cues in native target tissues.
Collapse
Affiliation(s)
- Bradley W Tuft
- Department of Chemical and Biochemical Engineering, University of Iowa, Iowa City, IA, USA
| | - Linjing Xu
- Department of Otolaryngology - Head and Neck Surgery, University of Iowa, Iowa City, IA, USA
| | - Braden Leigh
- Department of Chemical and Biochemical Engineering, University of Iowa, Iowa City, IA, USA
| | - Daniel Lee
- Department of Otolaryngology - Head and Neck Surgery, University of Iowa, Iowa City, IA, USA
| | - C Allan Guymon
- Department of Chemical and Biochemical Engineering, University of Iowa, Iowa City, IA, USA
| | - Marlan R Hansen
- Department of Otolaryngology - Head and Neck Surgery, University of Iowa, Iowa City, IA, USA.,Department of Neurosurgery, University of Iowa, Iowa City, IA, USA
| |
Collapse
|
17
|
Gao M, Yu Y, Zhao H, Li G, Jiang H, Wang C, Cai F, Chan LLH, Chiu B, Qian W, Qiu W, Zheng H. Simulation Study of an Ultrasound Retinal Prosthesis With a Novel Contact-Lens Array for Noninvasive Retinal Stimulation. IEEE Trans Neural Syst Rehabil Eng 2017; 25:1605-1611. [PMID: 28320674 DOI: 10.1109/tnsre.2017.2682923] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Millions of people around the world suffer from varying degrees of vision loss (including complete blindness) because of retinal degenerative diseases. Artificial retinal prosthesis, which is usually based on electrical neurostimulation, is the most advanced technology for different types of retinal degeneration. However, this technology involves placing a device into the eyeball, and such a highly invasive procedure is inevitably highly risk and expensive. Ultrasound has been demonstrated to be a promising technology for noninvasive neurostimulation, making it possible to stimulate the retina and induce action potentials similar to those elicited by light stimulation. However, the technology of ultrasound retinal stimulation still requires considerable developments before it could be applied clinically. This paper proposes a novel contact-lens array transducer for use in an ultrasound retinal prosthesis (USRP). The transducer was designed in the shape of a contact lens so as to facilitate acoustic coupling with the eye liquid. The key parameters of the ultrasound transducer were simulated, and results are presented that indicate the achievement of 2-D pattern generation and that the proposed contact-lens array is suitable for multiple-focus neurostimulation, and can be used in a USRP.
Collapse
|
18
|
Aharony I, Michowiz S, Goldenberg-Cohen N. The promise of stem cell-based therapeutics in ophthalmology. Neural Regen Res 2017; 12:173-180. [PMID: 28400789 PMCID: PMC5361491 DOI: 10.4103/1673-5374.200793] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The promising role of cellular therapies in the preservation and restoration of visual function has prompted intensive efforts to characterize embryonic, adult, and induced pluripotent stem cells for regenerative purposes. Three main approaches to the use of stem cells have been described: sustained drug delivery, immunomodulation, and differentiation into various ocular structures. Studies of the differentiation capacity of all three types of stem cells into epithelial, neural, glial and vascular phenotypes have reached proof-of-concept in culture, but the correction of vision is still in the early developmental stages, and the requirements for effective in vivo implementation are still unclear. We present an overview of some of the preclinical findings on stem-cell rescue and regeneration of the cornea and retina in acute injury and degenerative disorders.
Collapse
Affiliation(s)
- Israel Aharony
- The Krieger Eye Research Laboratory, Felsenstein Medical Research Center, Petach Tikva, Israel; Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Shalom Michowiz
- The Krieger Eye Research Laboratory, Felsenstein Medical Research Center, Petach Tikva, Israel; Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel; Department of Neurosurgery, Rabin Medical Center - Beilinson Hospital, Petach Tikva, Israel
| | - Nitza Goldenberg-Cohen
- The Krieger Eye Research Laboratory, Felsenstein Medical Research Center, Petach Tikva, Israel; Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel; Department of Ophthalmology, Bnai Zion Medical Center, Haifa, Israel
| |
Collapse
|
19
|
Lai JY, Li YT. Influence of Cross-Linker Concentration on the Functionality of Carbodiimide Cross-Linked Gelatin Membranes for Retinal Sheet Carriers. JOURNAL OF BIOMATERIALS SCIENCE-POLYMER EDITION 2016; 22:277-95. [PMID: 20557713 DOI: 10.1163/092050609x12603600753204] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Carbodiimide cross-linking can easily regulate the functionality of gelatin carriers used for retinal sheet delivery. This paper investigates the effect of cross-linker concentrations (0-0.4 mmol EDC/mg gelatin membrane (GM)) on the properties of the chemically-modified GMs. ATR-FT-IR and ninhydrin analyses results consistently indicated that the EDC cross-linking reaction approaches saturation at concentrations around 0.02 mmol EDC/mg GM. The thermal stability and resistance to water dissolution and collagenase digestion were significantly enhanced with increasing cross-linker concentration from 0.001 to 0.02 mmol EDC/mg GM. In addition, the chemical cross-linking did not affect the ability to form a tissue-encapsulating structure at 37°C. Irrespective of their cross-linking degree, the GMs had an appropriate degradation rate sufficient to allow tissue integration. It was noted that, although high cross-linker concentrations can be used to improve the delivery efficiency of gelatin samples, the treatment with 0.1-0.4 mmol EDC/mg GM may lead to poor biocompatibility. Results of Live/Dead and pro-inflammatory cytokine expression analyses showed that the exposure of ARPE-19 cultures to the test materials cross-linked with a concentration ≥0.1 mmol EDC/mg GM induces significant cytotoxicity and high levels of interleukin-1β and interleukin-6. However, the presence of EDC cross-linked gelatin membranes in the culture medium had no effect on the glutamate uptake capacity. It is concluded that among the cross-linked gelatin samples studied, 0.02 mmol EDC/mg GM is the best cross-linker concentration for preparation of retinal sheet delivery carriers.
Collapse
Affiliation(s)
- Jui-Yang Lai
- a Institute of Biochemical and Biomedical Engineering, Chang Gung University, Taoyuan, Taiwan 33302, Republic of China; Biomedical Engineering Research Center, Chang Gung University, Taoyuan, Taiwan 33302, Republic of China; Molecular Medicine Research Center, Chang Gung University, Taoyuan, Taiwan 33302, Republic of China
| | | |
Collapse
|
20
|
Cao X, Sui X, Lyu Q, Li L, Chai X. Effects of different three-dimensional electrodes on epiretinal electrical stimulation by modeling analysis. J Neuroeng Rehabil 2015; 12:73. [PMID: 26311232 PMCID: PMC4551567 DOI: 10.1186/s12984-015-0065-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2014] [Accepted: 08/19/2015] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Epiretinal prostheses have been greatly successful in helping restore the vision of patients blinded by retinal degenerative diseases. The design of stimulating electrodes plays a crucial role in the performance of epiretinal prostheses. The objective of this study was to investigate, through computational modeling analysis, the effects on the excitation of retinal ganglion cells (RGCs) when different three-dimensional (3-D) electrodes were placed in the epiretinal space. METHODS 3-D finite element models of retinal electrical stimulation were created in COMSOL using a platinum microelectrode, a vitreous body, multi-layered retinal tissue, and retinal pigment epithelium (RPE). Disk and non-planar electrodes with different 3-D structures were used in the epiretinal electrical stimulation. In addition, a multi-RGC model including ionic mechanisms was constructed in NEURON to study the excitability of RGCs in response to epiretinal electrical stimulation by different types of electrodes. Threshold current, threshold charge density, and the activated RGC area were the three key factors used to evaluate the stimulating electrode's performance. RESULTS As the electrode-retina distance increased, both threshold current and threshold charge density showed an approximately linear relationship. Increasing the disk electrode's diameter resulted in an increase in threshold current and a decrease in threshold charge density. Non-planar electrodes evoked different activation responses in RGCs than the disk electrode. Concave electrodes produced superior stimulation localization and electrode safety while convex electrodes performed relatively poorly. CONCLUSIONS Investigation of epiretinal electrical stimulation using different 3-D electrodes would further the optimization of electrode design and help improve the performance of epiretinal prostheses. The combination of finite element analysis in COMSOL and NEURON software provides an efficient way to evaluate the influences of various 3-D electrodes on epiretinal electrical stimulation. Non-planar electrodes had larger threshold currents than disk electrodes. Of the five types of electrodes, concave hemispherical electrodes may be the ideal option, considering their superior stimulation localization and electrode safety.
Collapse
Affiliation(s)
- Xun Cao
- School of Biomedical Engineering, Shanghai Jiao Tong University, No.800 Dongchuan Road, Shanghai, People's Republic of China.
| | - Xiaohong Sui
- School of Biomedical Engineering, Shanghai Jiao Tong University, No.800 Dongchuan Road, Shanghai, People's Republic of China.
| | - Qing Lyu
- School of Biomedical Engineering, Shanghai Jiao Tong University, No.800 Dongchuan Road, Shanghai, People's Republic of China.
| | - Liming Li
- School of Biomedical Engineering, Shanghai Jiao Tong University, No.800 Dongchuan Road, Shanghai, People's Republic of China.
| | - Xinyu Chai
- School of Biomedical Engineering, Shanghai Jiao Tong University, No.800 Dongchuan Road, Shanghai, People's Republic of China.
| |
Collapse
|
21
|
Ghezzi D. Retinal prostheses: progress toward the next generation implants. Front Neurosci 2015; 9:290. [PMID: 26347602 PMCID: PMC4542462 DOI: 10.3389/fnins.2015.00290] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2015] [Accepted: 07/30/2015] [Indexed: 12/18/2022] Open
Abstract
In the last decade, various clinical trials proved the capability of visual prostheses, in particular retinal implants, to restore a useful form of vision. These encouraging results promoted the emerging of several strategies for neuronal stimulation aiming at the restoration of sight. Besides the traditional approach based on electrical stimulation through metal electrodes in the different areas of the visual path (e.g., the visual cortex, the lateral geniculate nucleus, the optic nerve, and the retina), novel concepts for neuronal stimulation have been mostly exploited as building blocks of the next generation of retinal implants. This review is focused on critically discussing recent major advancements in the field of retinal stimulation with particular attention to the findings in the application of novel concepts and materials. Last, the major challenges in the field and their clinical implications will be outlined.
Collapse
Affiliation(s)
- Diego Ghezzi
- Medtronic Chair in Neuroengineering, Center for Neuroprosthetics, Interfaculty Institute of Bioengineering, School of Engineering, École Polytechnique Fédérale de Lausanne Lausanne, Switzerland
| |
Collapse
|
22
|
Guadagni V, Novelli E, Piano I, Gargini C, Strettoi E. Pharmacological approaches to retinitis pigmentosa: A laboratory perspective. Prog Retin Eye Res 2015; 48:62-81. [PMID: 26113212 DOI: 10.1016/j.preteyeres.2015.06.005] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2015] [Revised: 06/05/2015] [Accepted: 06/11/2015] [Indexed: 01/08/2023]
Abstract
Retinal photoreceptors are highly specialized and performing neurons. Their cellular architecture is exquisitely designed to host a high concentration of molecules involved in light capture, phototransduction, electric and chemical signaling, membrane and molecular turnover, light and dark adaption, network activities etc. Such high efficiency and molecular complexity require a great metabolic demand, altogether conferring to photoreceptors particular susceptibility to external and internal insults, whose occurrence usually precipitate into degeneration of these cells and blindness. In Retinitis Pigmentosa, an impressive number of mutations in genes expressed in the retina and coding for a large varieties of proteins leads to the progressive death of photoreceptors and blindness. Recent advances in molecular tools have greatly facilitated the identification of the underlying genetics and molecular bases of RP leading to the successful implementation of gene therapy for some types of mutations, with visual restoration in human patients. Yet, genetic heterogeneity of RP makes mutation-independent approaches highly desirable, although many obstacles pave the way to general strategies for treating this complex disease, which remains orphan. The review will focus on treatments for RP based on pharmacological tools, choosing, among the many ongoing studies, approaches which rely on strong experimental evidence or rationale. For perspective treatments, new concepts are foreseen to emerge from basic studies elucidating the pathways connecting the primary mutations to photoreceptor death, possibly revealing common molecular targets for drug intervention.
Collapse
Affiliation(s)
- Viviana Guadagni
- Neuroscience Institute, Italian National Research Council (CNR), Area della Ricerca, Via Giuseppe Moruzzi 1, 56124 Pisa, Italy
| | - Elena Novelli
- Neuroscience Institute, Italian National Research Council (CNR), Area della Ricerca, Via Giuseppe Moruzzi 1, 56124 Pisa, Italy
| | - Ilaria Piano
- Department of Pharmacy, University of Pisa, Pisa, Italy
| | | | - Enrica Strettoi
- Neuroscience Institute, Italian National Research Council (CNR), Area della Ricerca, Via Giuseppe Moruzzi 1, 56124 Pisa, Italy.
| |
Collapse
|
23
|
Tochitsky I, Kramer RH. Optopharmacological tools for restoring visual function in degenerative retinal diseases. Curr Opin Neurobiol 2015; 34:74-8. [PMID: 25706312 DOI: 10.1016/j.conb.2015.01.018] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2015] [Revised: 01/26/2015] [Accepted: 01/28/2015] [Indexed: 11/17/2022]
Abstract
Retinitis pigmentosa (RP) and age-related macular degeneration (AMD) are progressive retinal diseases that result from the death of rod and cone photoreceptors, ultimately leading to blindness. The only currently approved vision restoration treatment employs an implanted retinal 'chip' as a prosthetic device to electrically stimulate retinal neurons that survive after the photoreceptors are gone, thereby restoring light-driven neural signaling to the brain. Alternative strategies have been proposed, which would utilize optogenetic or optopharmacological tools to enable direct optical stimulation of surviving retinal neurons. Here, we review the latest studies evaluating the feasibility of these molecular tools as potential therapeutics for restoring visual function in human blinding disease.
Collapse
Affiliation(s)
- Ivan Tochitsky
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA
| | - Richard H Kramer
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA.
| |
Collapse
|
24
|
Xiang Z, Yen SC, Sheshadri S, Xue N, Lee SH, Wang J, Thakor NV, Lee C. Flexible and self-adaptive neural ribbon with three-dimensional electrodes for sciatic nerve recording. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2015; 2015:3157-3160. [PMID: 26736962 DOI: 10.1109/embc.2015.7319062] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Various peripheral nerve interfaces have been developed in the last decades and transferred into neuroscientific researches or clinical applications. In this study, we present a novel flexible neural ribbon electrode that can achieve self-adaption to nerves in various diameters and have three dimensional (3D) contacts. Impedance spectroscopy of the neural ribbon electrode was carried out to determine its electrochemical characteristics during the recording. The recording capability of the neural ribbon on sciatic nerves with different diameter was demonstrated by successful signal acquisitions.
Collapse
|
25
|
Tuft BW, Zhang L, Xu L, Hangartner A, Leigh B, Hansen MR, Guymon CA. Material stiffness effects on neurite alignment to photopolymerized micropatterns. Biomacromolecules 2014; 15:3717-27. [PMID: 25211120 PMCID: PMC4195519 DOI: 10.1021/bm501019s] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The ability to direct neurite growth into a close proximity of stimulating elements of a neural prosthesis, such as a retinal or cochlear implant (CI), may enhance device performance and overcome current spatial signal resolution barriers. In this work, spiral ganglion neurons (SGNs), which are the target neurons to be stimulated by CIs, were cultured on photopolymerized micropatterns with varied matrix stiffnesses to determine the effect of rigidity on neurite alignment to physical cues. Micropatterns were generated on methacrylate thin film surfaces in a simple, rapid photopolymerization step by photomasking the prepolymer formulation with parallel line-space gratings. Two methacrylate series, a nonpolar HMA-co-HDDMA series and a polar PEGDMA-co-EGDMA series, with significantly different surface wetting properties were evaluated. Equivalent pattern periodicity was maintained across each methacrylate series based on photomask band spacing, and the feature amplitude was tuned to a depth of 2 μm amplitude for all compositions using the temporal control afforded by the UV curing methodology. The surface morphology was characterized by scanning electron microscopy and white light interferometry. All micropatterned films adsorb similar amounts of laminin from solution, and no significant difference in SGN survival was observed when the substrate compositions were compared. SGN neurite alignment significantly increases with increasing material modulus for both methacrylate series. Interestingly, SGN neurites respond to material stiffness cues that are orders of magnitude higher (GPa) than what is typically ascribed to neural environments (kPa). The ability to understand neurite response to engineered physical cues and mechanical properties such as matrix stiffness will allow the development of advanced biomaterials that direct de novo neurite growth to address the spatial signal resolution limitations of current neural prosthetics.
Collapse
Affiliation(s)
- Bradley W Tuft
- Department of Chemical and Biochemical Engineering, University of Iowa , Iowa City, Iowa 52242, United States
| | | | | | | | | | | | | |
Collapse
|
26
|
Tuft BW, Xu L, White SP, Seline AE, Erwood AM, Hansen MR, Guymon CA. Neural pathfinding on uni- and multidirectional photopolymerized micropatterns. ACS APPLIED MATERIALS & INTERFACES 2014; 6:11265-76. [PMID: 24911660 PMCID: PMC4215840 DOI: 10.1021/am501622a] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/17/2014] [Accepted: 06/09/2014] [Indexed: 05/22/2023]
Abstract
Overcoming signal resolution barriers of neural prostheses, such as the commercially available cochlear impant (CI) or the developing retinal implant, will likely require spatial control of regenerative neural elements. To rationally design materials that direct nerve growth, it is first necessary to determine pathfinding behavior of de novo neurite growth from prosthesis-relevant cells such as spiral ganglion neurons (SGNs) in the inner ear. Accordingly, in this work, repeating 90° turns were fabricated as multidirectional micropatterns to determine SGN neurite turning capability and pathfinding. Unidirectional micropatterns and unpatterned substrates are used as comparisons. Spiral ganglion Schwann cell alignment (SGSC) is also examined on each surface type. Micropatterns are fabricated using the spatial reaction control inherent to photopolymerization with photomasks that have either parallel line spacing gratings for unidirectional patterns or repeating 90° angle steps for multidirectional patterns. Feature depth is controlled by modulating UV exposure time by shuttering the light source at given time increments. Substrate topography is characterized by white light interferometry and scanning electron microscopy (SEM). Both pattern types exhibit features that are 25 μm in width and 7.4 ± 0.7 μm in depth. SGN neurites orient randomly on unpatterned photopolymer controls, align and consistently track unidirectional patterns, and are substantially influenced by, but do not consistently track, multidirectional turning cues. Neurite lengths are 20% shorter on multidirectional substrates compared to unidirectional patterns while neurite branching and microfeature crossing events are significantly higher. For both pattern types, the majority of the neurite length is located in depressed surface features. Developing methods to understand neural pathfinding and to guide de novo neurite growth to specific stimulatory elements will enable design of innovative biomaterials that improve functional outcomes of devices that interface with the nervous system.
Collapse
Affiliation(s)
- Bradley W. Tuft
- Department
of Chemical and Biochemical Engineering, University of Iowa, Iowa City, Iowa 52242,
United States, United States
| | - Linjing Xu
- Department
of Otolaryngology, University of Iowa Hospitals
and Clinics, Iowa City, Iowa 52242, United States, United States
| | - Scott P. White
- Department
of Chemical and Biochemical Engineering, University of Iowa, Iowa City, Iowa 52242,
United States, United States
| | - Alison E. Seline
- Department
of Otolaryngology, University of Iowa Hospitals
and Clinics, Iowa City, Iowa 52242, United States, United States
| | - Andrew M. Erwood
- Department
of Otolaryngology, University of Iowa Hospitals
and Clinics, Iowa City, Iowa 52242, United States, United States
| | - Marlan R. Hansen
- Department
of Otolaryngology, University of Iowa Hospitals
and Clinics, Iowa City, Iowa 52242, United States, United States
| | - C. Allan Guymon
- Department
of Chemical and Biochemical Engineering, University of Iowa, Iowa City, Iowa 52242,
United States, United States
- Tel.:(319)335-5015
| |
Collapse
|
27
|
Rowe-Rendleman CL, Durazo SA, Kompella UB, Rittenhouse KD, Di Polo A, Weiner AL, Grossniklaus HE, Naash MI, Lewin AS, Horsager A, Edelhauser HF. Drug and gene delivery to the back of the eye: from bench to bedside. Invest Ophthalmol Vis Sci 2014; 55:2714-30. [PMID: 24777644 DOI: 10.1167/iovs.13-13707] [Citation(s) in RCA: 84] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
|
28
|
Fattahi P, Yang G, Kim G, Abidian MR. A review of organic and inorganic biomaterials for neural interfaces. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2014; 26:1846-85. [PMID: 24677434 PMCID: PMC4373558 DOI: 10.1002/adma.201304496] [Citation(s) in RCA: 300] [Impact Index Per Article: 30.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/06/2013] [Revised: 10/08/2013] [Indexed: 05/18/2023]
Abstract
Recent advances in nanotechnology have generated wide interest in applying nanomaterials for neural prostheses. An ideal neural interface should create seamless integration into the nervous system and performs reliably for long periods of time. As a result, many nanoscale materials not originally developed for neural interfaces become attractive candidates to detect neural signals and stimulate neurons. In this comprehensive review, an overview of state-of-the-art microelectrode technologies provided fi rst, with focus on the material properties of these microdevices. The advancements in electro active nanomaterials are then reviewed, including conducting polymers, carbon nanotubes, graphene, silicon nanowires, and hybrid organic-inorganic nanomaterials, for neural recording, stimulation, and growth. Finally, technical and scientific challenges are discussed regarding biocompatibility, mechanical mismatch, and electrical properties faced by these nanomaterials for the development of long-lasting functional neural interfaces.
Collapse
Affiliation(s)
- Pouria Fattahi
- Biomedical Engineering Department and Chemical Engineering Departments, Pennsylvania State University, University Park, PA, 16802, USA
| | - Guang Yang
- Biomedical Engineering Department, Pennsylvania State University, University Park, PA, 16802, USA
| | - Gloria Kim
- Biomedical Engineering Department, Pennsylvania State University, University Park, PA, 16802, USA
| | - Mohammad Reza Abidian
- Biomedical Engineering Department, Materials Science & Engineering Department, Chemical Engineering Department, Materials Research Institute, Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, PA, 16802, USA
| |
Collapse
|
29
|
Depan D, Misra RDK. The development, characterization, and cellular response of a novel electroactive nanostructured composite for electrical stimulation of neural cells. Biomater Sci 2014; 2:1727-1739. [DOI: 10.1039/c4bm00168k] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Electrical stimulation induced cytoskeletal protein reorganization of neural cells on a PEDOT-CNT coated stainless steel neural probe.
Collapse
Affiliation(s)
- D. Depan
- Biomaterials and Biomedical Engineering Research Laboratory
- Center for Structural and Functional Materials
- University of Louisiana at Lafayette
- Lafayette, USA
| | - R. D. K. Misra
- Biomaterials and Biomedical Engineering Research Laboratory
- Center for Structural and Functional Materials
- University of Louisiana at Lafayette
- Lafayette, USA
| |
Collapse
|
30
|
Tønnesen J. Optogenetic cell control in experimental models of neurological disorders. Behav Brain Res 2013; 255:35-43. [PMID: 23871610 DOI: 10.1016/j.bbr.2013.07.007] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2013] [Revised: 06/16/2013] [Accepted: 07/06/2013] [Indexed: 01/05/2023]
Abstract
The complexity of the brain, in which different neuronal cell types are interspersed and complexly interconnected, has posed a major obstacle in identifying pathophysiological mechanisms underlying prevalent neurological disorders. This is largely based in the inability of classical experimental approaches to target defined neural populations at sufficient temporal and spatial resolution. As a consequence, effective clinical therapies for prevalent neurological disorders are largely lacking. Recently developed optogenetic probes are genetically expressed photosensitive ion channels and pumps that in principal overcome these limitations. Optogenetic probes allow millisecond resolution functional control over selected optogenetically transduced neuronal populations targeted based on promoter activity. This optical cell control scheme has already been applied to answer fundamental questions pertaining to neurological disorders by allowing researchers to experimentally intercept, or induce, pathophysiological neuronal signaling activity in a highly controlled manner. Offering high temporal resolution control over neural activity at high cellular specificity, optogenetic tools constitute a game changer in research aiming at understanding pathophysiological signaling mechanisms in neurological disorders and in developing therapeutic strategies to correct these. In this regard, recent experimental work has provided new insights in underlying mechanisms, as well as preliminary proof-of-principle for optogenetic therapies, of several neurological disorders, including Parkinson's disease, epilepsy and progressive blindness. This review synthesizes experimental work where optogenetic tools have been applied to explore pathologic neural network activity in models of neurological disorders.
Collapse
Affiliation(s)
- Jan Tønnesen
- Experimental Epilepsy Group, Division of Neurology, Wallenberg Neuroscience Center, Lund University Hospital, Lund, Sweden; Synaptic Plasticity and Superresolution Microscopy Group, Interdisciplinary Institute for Neuroscience and UMR 5297 CNRS/Université Bordeaux Segalen, Bordeaux, France.
| |
Collapse
|
31
|
Zhou H, Cheng X, Rao L, Li T, Duan YY. Poly(3,4-ethylenedioxythiophene)/multiwall carbon nanotube composite coatings for improving the stability of microelectrodes in neural prostheses applications. Acta Biomater 2013; 9:6439-49. [PMID: 23402765 DOI: 10.1016/j.actbio.2013.01.042] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2012] [Revised: 01/26/2013] [Accepted: 01/31/2013] [Indexed: 02/02/2023]
Abstract
With the purpose of improving the stability of microelectrodes under continuous high charge density stimulation, which is required for neural prostheses applications such as visual prostheses, multiwall carbon nanotube (MWCNT)-doped poly(3,4-ethylenedioxythiophene) (PEDOT) composite films were coated onto a platinum microelectrode by electrochemical polymerization. Galvanostatically polymerized PEDOT/MWCNT films demonstrated superior characteristics compared to polystyrene sulfonate doping and potentiostatic polymerization, including a three-dimensional cone morphology and enhanced electrochemical performance (the safe charge injection limit reached 6.2 mC cm(-2) for cathodic-first pulses). Most important of all, the improved stability of the coatings has been revealed through stimulation for 96 h using 3.0 mCc m(-2) current pulses in bicarbonate- and phosphate-buffered saline solution. Cell assays revealed that PEDOT/MWCNT films could promote the adhesion and neurite outgrowth of rat pheochromocytoma cells. Finally, platinum wires coated with PEDOT/MWCNT films were implanted into rat cortex for 6 weeks for histological evaluation. Glial fibrillary acidic protein and neuronal nuclei staining revealed that the films elicit a lower tissue response compared to platinum implants. These results suggest that the galvanostatically polymerized PEDOT/MWCNT films can improve the stability of stimulation microelectrodes and that PEDOT/MWCNT is an excellent candidate material for electrode coating for neural prostheses applications.
Collapse
|
32
|
Polosukhina A, Litt J, Tochitsky I, Nemargut J, Sychev Y, De Kouchkovsky I, Huang T, Borges K, Trauner D, Van Gelder RN, Kramer RH. Photochemical restoration of visual responses in blind mice. Neuron 2012; 75:271-82. [PMID: 22841312 DOI: 10.1016/j.neuron.2012.05.022] [Citation(s) in RCA: 174] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/30/2012] [Indexed: 11/25/2022]
Abstract
Retinitis pigmentosa (RP) and age-related macular degeneration (AMD) are degenerative blinding diseases caused by the death of rods and cones, leaving the remainder of the visual system intact but largely unable to respond to light. Here, we show that AAQ, a synthetic small molecule photoswitch, can restore light sensitivity to the retina and behavioral responses in vivo in mouse models of RP, without exogenous gene delivery. Brief application of AAQ bestows prolonged light sensitivity on multiple types of retinal neurons, resulting in synaptically amplified responses and center-surround antagonism in arrays of retinal ganglion cells (RGCs). Intraocular injection of AAQ restores the pupillary light reflex and locomotory light avoidance behavior in mice lacking retinal photoreceptors, indicating reconstitution of light signaling to brain circuits. AAQ and related photoswitch molecules present a potential drug strategy for restoring retinal function in degenerative blinding diseases.
Collapse
Affiliation(s)
- Aleksandra Polosukhina
- Vision Science Graduate Group, University of California, Berkeley, Berkeley, CA 94720, USA
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
33
|
Photopolymerized microfeatures for directed spiral ganglion neurite and Schwann cell growth. Biomaterials 2012; 34:42-54. [PMID: 23069708 DOI: 10.1016/j.biomaterials.2012.09.053] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2012] [Accepted: 09/23/2012] [Indexed: 12/15/2022]
Abstract
Cochlear implants (CIs) provide auditory perception to individuals with severe hearing impairment. However, their ability to encode complex auditory stimuli is limited due, in part, to poor spatial resolution caused by electrical current spread in the inner ear. Directing nerve cell processes towards target electrodes may reduce the problematic current spread and improve stimulatory specificity. In this work, photopolymerization was used to fabricate micro- and nano-patterned methacrylate polymers to probe the extent of spiral ganglion neuron (SGN) neurite and Schwann cell (SGSC) contact guidance based on variations in substrate topographical cues. Micropatterned substrates are formed in a rapid, single-step reaction by selectively blocking light with photomasks which have parallel line-space gratings with periodicities of 10-100 μm. Channel amplitudes of 250 nm-10 μm are generated by modulating UV exposure time, light intensity, and photoinitiator concentration. Gradual transitions are observed between ridges and grooves using scanning electron and atomic force microscopy. The transitions stand in contrast to vertical features generated via etching lithographic techniques. Alignment of neural elements increases significantly with increasing feature amplitude and constant periodicity, as well as with decreasing periodicity and constant amplitude. SGN neurite alignment strongly correlates (r = 0.93) with maximum feature slope. Multiple neuronal and glial types orient to the patterns with varying degrees of alignment. This work presents a method to fabricate gradually-sloping micropatterns for cellular contact guidance studies and demonstrates spatial control of inner ear neural elements in response to micro- and nano-scale surface topography.
Collapse
|
34
|
Bansal AK, Singer JM, Anderson WS, Golby A, Madsen JR, Kreiman G. Temporal stability of visually selective responses in intracranial field potentials recorded from human occipital and temporal lobes. J Neurophysiol 2012; 108:3073-86. [PMID: 22956795 DOI: 10.1152/jn.00458.2012] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The cerebral cortex needs to maintain information for long time periods while at the same time being capable of learning and adapting to changes. The degree of stability of physiological signals in the human brain in response to external stimuli over temporal scales spanning hours to days remains unclear. Here, we quantitatively assessed the stability across sessions of visually selective intracranial field potentials (IFPs) elicited by brief flashes of visual stimuli presented to 27 subjects. The interval between sessions ranged from hours to multiple days. We considered electrodes that showed robust visual selectivity to different shapes; these electrodes were typically located in the inferior occipital gyrus, the inferior temporal cortex, and the fusiform gyrus. We found that IFP responses showed a strong degree of stability across sessions. This stability was evident in averaged responses as well as single-trial decoding analyses, at the image exemplar level as well as at the category level, across different parts of visual cortex, and for three different visual recognition tasks. These results establish a quantitative evaluation of the degree of stationarity of visually selective IFP responses within and across sessions and provide a baseline for studies of cortical plasticity and for the development of brain-machine interfaces.
Collapse
Affiliation(s)
- Arjun K Bansal
- Department of Ophthalmology, Boston Children’s Hospital, Harvard Medical School, Boston, MA, USA
| | | | | | | | | | | |
Collapse
|
35
|
Damiani D, Novelli E, Mazzoni F, Strettoi E. Undersized dendritic arborizations in retinal ganglion cells of the rd1 mutant mouse: a paradigm of early onset photoreceptor degeneration. J Comp Neurol 2012; 520:1406-23. [PMID: 22102216 DOI: 10.1002/cne.22802] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Retinitis pigmentosa (RP) is a family of inherited diseases causing progressive photoreceptor death. Retinal ganglion cells (RGCs) form the biological substrate for various therapeutic approaches designed to restore vision in RP individuals. Assessment of survival and preservation of RGCs in animal paradigms mimicking the human disease is of key importance for appropriate implementation of vision repair strategies. Here we studied the survival of RGCs in the rd1 mutant mouse, a known model of early onset, autosomic recessive RP, at various stages of photoreceptor degeneration. Furthermore, we analyzed the morphology of various types of RGCs using the newly generated transgenic mouse rd1/Thy1-GFP, in which the rd1 mutation is associated with green fluorescent protein (GFP) expression in a small population of different RGCs. We found excellent survival of cells at up to 1 year of age, a time at which the inner retina is known to have severely reorganized and partially degenerated. However, 50% of the cells analyzed within all RGC types exhibit an undersized dendritic tree, spanning about half of the normal area. Undersized cells are found both in adult and in very young (1-month-old) mice. This suggests that their aberrant phenotype is due to incomplete dendritic development, possibly as a consequence of altered visual input at the time of dendritic arbor refinement. These data show the importance of the timing of photoreceptor death in RGC dendritic development.
Collapse
Affiliation(s)
- Devid Damiani
- Neuroscience Institute, National Research Council of Italy, CNR, Pisa, Italy
| | | | | | | |
Collapse
|
36
|
Retinal prosthetic strategy with the capacity to restore normal vision. Proc Natl Acad Sci U S A 2012; 109:15012-7. [PMID: 22891310 DOI: 10.1073/pnas.1207035109] [Citation(s) in RCA: 129] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Retinal prosthetics offer hope for patients with retinal degenerative diseases. There are 20-25 million people worldwide who are blind or facing blindness due to these diseases, and they have few treatment options. Drug therapies are able to help a small fraction of the population, but for the vast majority, their best hope is through prosthetic devices [reviewed in Chader et al. (2009) Prog Brain Res 175:317-332]. Current prosthetics, however, are still very limited in the vision that they provide: for example, they allow for perception of spots of light and high-contrast edges, but not natural images. Efforts to improve prosthetic capabilities have focused largely on increasing the resolution of the device's stimulators (either electrodes or optogenetic transducers). Here, we show that a second factor is also critical: driving the stimulators with the retina's neural code. Using the mouse as a model system, we generated a prosthetic system that incorporates the code. This dramatically increased the system's capabilities--well beyond what can be achieved just by increasing resolution. Furthermore, the results show, using 9,800 optogenetically stimulated ganglion cell responses, that the combined effect of using the code and high-resolution stimulation is able to bring prosthetic capabilities into the realm of normal image representation.
Collapse
|
37
|
Khraiche ML, Lo Y, Wang D, Cauwenberghs G, Freeman W, Silva GA. Ultra-high photosensitivity silicon nanophotonics for retinal prosthesis: electrical characteristics. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2012; 2011:2933-6. [PMID: 22254955 DOI: 10.1109/iembs.2011.6090807] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Retinal degenerative diseases such as age related macular degeneration (AMD) and retinitis pigmentosa (RP), lead to the loss of the photoreceptor cells rendering the retina incapable of detecting light. Several engineering approaches have aimed at replacing the function of the photoreceptors by detecting light via an external camera or photodiodes and electrically stimulating the remaining retinal tissue to restore vision. These devices rely heavily on off-device processing to solve the computational challenge of matching the performance of the PRs. In this work, we present a unique ultra-high sensitivity photodetector technology with light sensitivity, signal amplification, light adaptation that shows signal transduction performance approaching those of the rods and cones in the mammalian retina. In addition, the technology offers nanoscale control over photodetectors topography with the potential to reproduce the visual acuity of the natural retina. This technology promises to drastically reduce the foot print, power consumption and computational needs of the current retinal prothesis, while reproducing high resolution vision.
Collapse
Affiliation(s)
- Massoud L Khraiche
- Department of Bioengineering, University of California, San Diego, CA, USA
| | | | | | | | | | | |
Collapse
|
38
|
Sundaram V, Moore AT, Ali RR, Bainbridge JW. Retinal dystrophies and gene therapy. Eur J Pediatr 2012; 171:757-65. [PMID: 22080959 DOI: 10.1007/s00431-011-1615-2] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/21/2011] [Accepted: 10/18/2011] [Indexed: 12/11/2022]
Abstract
Retinal dystrophies are inherited disorders of photoreceptor and retinal pigment epithelial function that may result in severe visual impairment. Advances in molecular genetics have helped identify many of the gene defects responsible, and progress in gene transfer technology has enabled therapeutic strategies to be developed and applied. The first human clinical trials of gene therapy for RPE65 associated retinal dystrophy have shown promising initial results and have helped prepare the way for further trials of gene therapy for inherited retinal disorders. The results of these trials will provide further insight into the safety and efficacy of gene therapy for a range of currently untreatable and debilitating eye disorders.
Collapse
Affiliation(s)
- Venki Sundaram
- Institute of Ophthalmology, University College London, 11-43 Bath Street, London, EC1V 9EL, UK
| | | | | | | |
Collapse
|
39
|
|
40
|
Garrett DJ, Ganesan K, Stacey A, Fox K, Meffin H, Prawer S. Ultra-nanocrystalline diamond electrodes: optimization towards neural stimulation applications. J Neural Eng 2011; 9:016002. [DOI: 10.1088/1741-2560/9/1/016002] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
|
41
|
Freeman DK, Jeng JS, Kelly SK, Hartveit E, Fried SI. Calcium channel dynamics limit synaptic release in response to prosthetic stimulation with sinusoidal waveforms. J Neural Eng 2011; 8:046005. [PMID: 21628768 PMCID: PMC3152377 DOI: 10.1088/1741-2560/8/4/046005] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Extracellular electric stimulation with sinusoidal waveforms has been shown to allow preferential activation of individual types of retinal neurons by varying stimulus frequency. It is important to understand the mechanisms underlying this frequency dependence as a step toward improving methods of preferential activation. In order to elucidate these mechanisms, we implemented a morphologically realistic model of a retinal bipolar cell and measured the response to extracellular stimulation with sinusoidal waveforms. We compared the frequency response of a passive membrane model to the kinetics of voltage-gated calcium channels that mediate synaptic release. The passive electrical properties of the membrane exhibited lowpass filtering with a relatively high cutoff frequency (nominal value = 717 Hz). This cutoff frequency was dependent on intra-axonal resistance, with shorter and wider axons yielding higher cutoff frequencies. However, we found that the cutoff frequency of bipolar cell synaptic release was primarily limited by the relatively slow opening kinetics of L- and T-type calcium channels. The cutoff frequency of calcium currents depended nonlinearly on stimulus amplitude, but remained lower than the cutoff frequency of the passive membrane model for a large range of membrane potential fluctuations. These results suggest that while it may be possible to modulate the membrane potential of bipolar cells over a wide range of stimulus frequencies, synaptic release will only be initiated at the lower end of this range.
Collapse
Affiliation(s)
- Daniel K Freeman
- Center for Innovative Visual Rehabilitation, Boston VA Healthcare System, 150 South Huntington Ave, Boston, MA 02130, USA
| | | | | | | | | |
Collapse
|
42
|
Djilas M, Olès C, Lorach H, Bendali A, Dégardin J, Dubus E, Lissorgues-Bazin G, Rousseau L, Benosman R, Ieng SH, Joucla S, Yvert B, Bergonzo P, Sahel J, Picaud S. Three-dimensional electrode arrays for retinal prostheses: modeling, geometry optimization and experimental validation. J Neural Eng 2011; 8:046020. [DOI: 10.1088/1741-2560/8/4/046020] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
|
43
|
Freeman DK, Rizzo JF, Fried SI. Encoding visual information in retinal ganglion cells with prosthetic stimulation. J Neural Eng 2011; 8:035005. [PMID: 21593546 PMCID: PMC3157751 DOI: 10.1088/1741-2560/8/3/035005] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Retinal prostheses aim to restore functional vision to those blinded by outer retinal diseases using electric stimulation of surviving retinal neurons. The ability to replicate the spatiotemporal pattern of ganglion cell spike trains present under normal viewing conditions is presumably an important factor for restoring high-quality vision. In order to replicate such activity with a retinal prosthesis, it is important to consider both how visual information is encoded in ganglion cell spike trains, and how retinal neurons respond to electric stimulation. The goal of the current review is to bring together these two concepts in order to guide the development of more effective stimulation strategies. We review the experiments to date that have studied how retinal neurons respond to electric stimulation and discuss these findings in the context of known retinal signaling strategies. The results from such in vitro studies reveal the advantages and disadvantages of activating the ganglion cell directly with the electric stimulus (direct activation) as compared to activation of neurons that are presynaptic to the ganglion cell (indirect activation). While direct activation allows high temporal but low spatial resolution, indirect activation yields improved spatial resolution but poor temporal resolution. Finally, we use knowledge gained from in vitro experiments to infer the patterns of elicited activity in ongoing human trials, providing insights into some of the factors limiting the quality of prosthetic vision.
Collapse
Affiliation(s)
- Daniel K Freeman
- Center for Innovative Visual Rehabilitation, Boston VA Healthcare System, 150 South Huntington Ave, Boston, MA 02130, USA.
| | | | | |
Collapse
|
44
|
Zrenner E, Bartz-Schmidt KU, Benav H, Besch D, Bruckmann A, Gabel VP, Gekeler F, Greppmaier U, Harscher A, Kibbel S, Koch J, Kusnyerik A, Peters T, Stingl K, Sachs H, Stett A, Szurman P, Wilhelm B, Wilke R. Subretinal electronic chips allow blind patients to read letters and combine them to words. Proc Biol Sci 2011; 278:1489-97. [PMID: 21047851 PMCID: PMC3081743 DOI: 10.1098/rspb.2010.1747] [Citation(s) in RCA: 625] [Impact Index Per Article: 48.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2010] [Accepted: 10/13/2010] [Indexed: 11/12/2022] Open
Abstract
A light-sensitive, externally powered microchip was surgically implanted subretinally near the macular region of volunteers blind from hereditary retinal dystrophy. The implant contains an array of 1500 active microphotodiodes ('chip'), each with its own amplifier and local stimulation electrode. At the implant's tip, another array of 16 wire-connected electrodes allows light-independent direct stimulation and testing of the neuron-electrode interface. Visual scenes are projected naturally through the eye's lens onto the chip under the transparent retina. The chip generates a corresponding pattern of 38 × 40 pixels, each releasing light-intensity-dependent electric stimulation pulses. Subsequently, three previously blind persons could locate bright objects on a dark table, two of whom could discern grating patterns. One of these patients was able to correctly describe and name objects like a fork or knife on a table, geometric patterns, different kinds of fruit and discern shades of grey with only 15 per cent contrast. Without a training period, the regained visual functions enabled him to localize and approach persons in a room freely and to read large letters as complete words after several years of blindness. These results demonstrate for the first time that subretinal micro-electrode arrays with 1500 photodiodes can create detailed meaningful visual perception in previously blind individuals.
Collapse
Affiliation(s)
- Eberhart Zrenner
- Centre for Ophthalmology, University of Tübingen, Schleichstr. 12, 72076 Tübingen, Germany.
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
45
|
Abramian M, Lovell NH, Morley JW, Suaning GJ, Dokos S. Activation of retinal ganglion cells following epiretinal electrical stimulation with hexagonally arranged bipolar electrodes. J Neural Eng 2011; 8:035004. [DOI: 10.1088/1741-2560/8/3/035004] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
|
46
|
Tamaki M, Matsuo T. Optical coherence tomographic parameters as objective signs for visual acuity in patients with retinitis pigmentosa, future candidates for retinal prostheses. J Artif Organs 2011; 14:140-50. [PMID: 21505820 DOI: 10.1007/s10047-011-0557-9] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2010] [Accepted: 02/02/2011] [Indexed: 10/18/2022]
Abstract
To find optical coherence tomographic parameters related with visual acuity, and, thus, which might be used as objective signs to predict visual acuity after future treatment, for example retinal prosthesis implantation, 86 eyes of 45 consecutive patients with retinitis pigmentosa, who showed no macular diseases, underwent optical coherence tomography to measure macular retinal thickness and peripapillary retinal nerve fiber layer (RNFL) thickness, and to obtain horizontal cross-sectional images at the fovea for observation of the inner segment/outer segment (IS/OS) junction line. Best-corrected visual acuity was significantly better either in the right eyes or in the left eyes with greater retinal thickness of all four quadrants of the macular area in the inner ring, encompassing 1-3 mm from the foveal center (P < 0.05, Spearman rank correlation test), and also with the presence of the IS/OS line at the fovea (P < 0.0001, Wilcoxon-Kruskal-Wallis rank sum test). Retinal average thickness in the posterior pole covering the 6 × 6 mm square area was positively correlated with peripapillary RNFL average thickness either in the right eyes or in the left eyes (P < 0.05). The average thickness of the peripapillary RNFL became significantly less with age (P < 0.05), but was not related with visual acuity. Macular retinal thickness and the presence of the IS/OS line, but not peripapillary RNFL thickness, could serve as objective signs for better visual acuity in retinitis pigmentosa. The macular retinal thickness might be used as an objective predictor to choose patients with retinitis pigmentosa who would be expected to gain vision after retinal prosthesis implantation.
Collapse
Affiliation(s)
- Miho Tamaki
- Department of Ophthalmology, Okayama University Medical School and Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Shikata-cho 2-5-1, Okayama, Japan
| | | |
Collapse
|
47
|
Sekirnjak C, Jepson LH, Hottowy P, Sher A, Dabrowski W, Litke AM, Chichilnisky EJ. Changes in physiological properties of rat ganglion cells during retinal degeneration. J Neurophysiol 2011; 105:2560-71. [PMID: 21389304 DOI: 10.1152/jn.01061.2010] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Retinitis pigmentosa (RP) is a leading cause of degenerative vision loss, yet its progressive effects on visual signals transmitted from the retina to the brain are not well understood. The transgenic P23H rat is a valuable model of human autosomal dominant RP, exhibiting extensive similarities to the human disease pathology, time course, and electrophysiology. In this study, we examined the physiological effects of degeneration in retinal ganglion cells (RGCs) of P23H rats aged between P37 and P752, and compared them with data from wild-type control animals. The strength and the size of visual receptive fields of RGCs decreased rapidly with age in P23H retinas. Light responses mediated by rod photoreceptors declined earlier (∼ P300) than cone-mediated light responses (∼ P600). Responses of ON and OFF RGCs diminished at a similar rate. However, OFF cells exhibited hyperactivity during degeneration, whereas ON cells showed a decrease in firing rate. The application of synaptic blockers abolished about half of the elevated firing in OFF RGCs, indicating that the remodeled circuitry was not the only source of degeneration-induced hyperactivity. These results advance our understanding of the functional changes associated with retinal degeneration.
Collapse
Affiliation(s)
- Chris Sekirnjak
- Salk Institute for Biological Studies, 10010 N. Torrey Pines Rd., La Jolla, CA 92037, USA
| | | | | | | | | | | | | |
Collapse
|
48
|
Freeman DK, Fried SI. Multiple components of ganglion cell desensitization in response to prosthetic stimulation. J Neural Eng 2011; 8:016008. [PMID: 21248379 PMCID: PMC3048167 DOI: 10.1088/1741-2560/8/1/016008] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Retinal prostheses aim to restore functional vision to those blinded by outer retinal diseases using electric stimulation of surviving neurons. Previous work indicates that repetitive stimulation with stimuli that activate the synaptic network reduces the sensitivity of retinal neurons to further stimulation. Such desensitization may contribute to the fading of visual percepts over time reported by human subjects. Here, we show that desensitization may be more complex than previously considered. We recorded spike trains from rabbit retinal ganglion cells and found that desensitization persists in the presence of inhibitory blockers (strychnine and picrotoxin), indicating amacrine cell inhibition is not solely responsible for reducing sensitivity in response to electric stimulation. The threshold for direct activation of the ganglion cell changes little during the simultaneous desensitization of the synaptically mediated response, indicating that desensitization likely occurs upstream of the spike generator. In addition to rapid desensitization acting over hundreds of milliseconds (τ = 176.4 ± 8.8 ms), we report the presence of slow acting desensitization with a time course of seconds (τ = 14.0 ± 1.1 s). The time courses of the two components of desensitization that we found are similar to the two phases of brightness fading seen in human subjects. This suggests that the reduction in ganglion cell firing due to desensitization may be responsible for the fading of visual percepts over time in response to prosthetic stimulation.
Collapse
Affiliation(s)
- Daniel K Freeman
- Center for Innovative Visual Rehabilitation, Boston VA Healthcare System, 150 South Huntington Ave, Boston, MA 02130, USA
| | | |
Collapse
|
49
|
Abstract
Once the topic of folklore and science fiction, the notion of restoring vision to the blind is now approaching a tractable reality. Technological advances have inspired numerous multidisciplinary groups worldwide to develop visual neuroprosthetic devices that could potentially provide useful vision and improve the quality of life of profoundly blind individuals. While a variety of approaches and designs are being pursued, they all share a common principle of creating visual percepts through the stimulation of visual neural elements using appropriate patterns of electrical stimulation. Human clinical trials are now well underway and initial results have been met with a balance of excitement and cautious optimism. As remaining technical and surgical challenges continue to be solved and clinical trials move forward, we now enter a phase of development that requires careful consideration of a new set of issues. Establishing appropriate patient selection criteria, methods of evaluating long-term performance and effectiveness, and strategies to rehabilitate implanted patients will all need to be considered in order to achieve optimal outcomes and establish these devices as viable therapeutic options.
Collapse
|
50
|
Dai C, Lu M, Zhao Y, Lu Y, Zhou C, Chen Y, Ren Q, Chai X. Correction for Chinese character patterns formed by simulated irregular phosphene map. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2010; 2010:5887-90. [PMID: 21096931 DOI: 10.1109/iembs.2010.5627528] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
To reduce the unfavorable influence of phosphene array irregularity on the form of Chinese character pattern so as to improve recognition accuracy in visual prostheses, two correction methods were put forward. One method was to generate phosphene closest to the target point in regular arrays using weighted nearest neighbor search. The other was to generate phosphene whose center located in the region covered by dilated characters. Based on a simulation system, Chinese character recognition tests were given to fifteen normally sighted subjects under five degrees of array irregularity (0.2, 0.4, 0.6, 0.8, 1.0) without correction. The recognition accuracy decreased with the increase of irregularity. When the recognition accuracy dropped below 80%, two correction methods were applied and their effects were evaluated. With the increase of array irregularity, both effects on the accuracy of recognition grew considerably. Comparison between the two methods revealed that the former method afforded higher recognition accuracy and the latter only applied to phosphene map with serious irregularity.
Collapse
Affiliation(s)
- Cong Dai
- Department of Biomedical Engineering, School of Life Sciences & Biotechnology, Shanghai Jiao Tong University, 200240, China
| | | | | | | | | | | | | | | |
Collapse
|