Mohajeet B. Bhuckory , Bing-Yi Wang , Zhijie C. Chen , Andrew Shin , Davis Pham-Howard , Sarthak Shah , Nicharee Monkongpitukkul , Ludwig Galambos , Theodore Kamins , Keith Mathieson , Daniel Palanker
{"title":"3D electronic implants in subretinal space: Long-term follow-up in rodents","authors":"Mohajeet B. Bhuckory , Bing-Yi Wang , Zhijie C. Chen , Andrew Shin , Davis Pham-Howard , Sarthak Shah , Nicharee Monkongpitukkul , Ludwig Galambos , Theodore Kamins , Keith Mathieson , Daniel Palanker","doi":"10.1016/j.biomaterials.2024.122674","DOIUrl":null,"url":null,"abstract":"<div><p>Clinical results with photovoltaic subretinal prosthesis (PRIMA) demonstrated restoration of sight via electrical stimulation of the interneurons in degenerated retina, with resolution matching the 100 μm pixel size. Since scaling the pixels below 75 μm in the current bipolar planar geometry will significantly limit the penetration depth of the electric field and increase stimulation threshold, we explore the possibility of using smaller pixels based on a novel 3-dimensional honeycomb-shaped design. We assessed the long-term biocompatibility and stability of these arrays in rats by investigating the anatomical integration of the retina with flat and 3D implants and response to electrical stimulation over lifetime – up to 32–36 weeks post-implantation in aged rats. With both flat and 3D implants, signals elicited in the visual cortex decreased after the day of implantation by more than 3-fold, and gradually recovered over the next 12–16 weeks. With 25 μm high honeycomb walls, the majority of bipolar cells migrate into the wells, while amacrine and ganglion cells remain above the cavities, which is essential for selective network-mediated stimulation of the retina. Retinal thickness and full-field stimulation threshold with 40 μm-wide honeycomb pixels were comparable to those with planar devices – 0.05 mW/mm<sup>2</sup> with 10 ms pulses. However, fewer cells from the inner nuclear layer migrated into the 20 μm-wide wells, and stimulation threshold increased over 12–16 weeks, before stabilizing at about 0.08 mW/mm<sup>2</sup>. Such threshold is still significantly lower than 1.8 mW/mm<sup>2</sup> with a previous design of flat bipolar pixels, confirming the promise of the 3D honeycomb-based approach to high resolution subretinal prosthesis.</p></div>","PeriodicalId":254,"journal":{"name":"Biomaterials","volume":null,"pages":null},"PeriodicalIF":12.8000,"publicationDate":"2024-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Biomaterials","FirstCategoryId":"5","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0142961224002084","RegionNum":1,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"ENGINEERING, BIOMEDICAL","Score":null,"Total":0}
引用次数: 0
Abstract
Clinical results with photovoltaic subretinal prosthesis (PRIMA) demonstrated restoration of sight via electrical stimulation of the interneurons in degenerated retina, with resolution matching the 100 μm pixel size. Since scaling the pixels below 75 μm in the current bipolar planar geometry will significantly limit the penetration depth of the electric field and increase stimulation threshold, we explore the possibility of using smaller pixels based on a novel 3-dimensional honeycomb-shaped design. We assessed the long-term biocompatibility and stability of these arrays in rats by investigating the anatomical integration of the retina with flat and 3D implants and response to electrical stimulation over lifetime – up to 32–36 weeks post-implantation in aged rats. With both flat and 3D implants, signals elicited in the visual cortex decreased after the day of implantation by more than 3-fold, and gradually recovered over the next 12–16 weeks. With 25 μm high honeycomb walls, the majority of bipolar cells migrate into the wells, while amacrine and ganglion cells remain above the cavities, which is essential for selective network-mediated stimulation of the retina. Retinal thickness and full-field stimulation threshold with 40 μm-wide honeycomb pixels were comparable to those with planar devices – 0.05 mW/mm2 with 10 ms pulses. However, fewer cells from the inner nuclear layer migrated into the 20 μm-wide wells, and stimulation threshold increased over 12–16 weeks, before stabilizing at about 0.08 mW/mm2. Such threshold is still significantly lower than 1.8 mW/mm2 with a previous design of flat bipolar pixels, confirming the promise of the 3D honeycomb-based approach to high resolution subretinal prosthesis.
期刊介绍:
Biomaterials is an international journal covering the science and clinical application of biomaterials. A biomaterial is now defined as a substance that has been engineered to take a form which, alone or as part of a complex system, is used to direct, by control of interactions with components of living systems, the course of any therapeutic or diagnostic procedure. It is the aim of the journal to provide a peer-reviewed forum for the publication of original papers and authoritative review and opinion papers dealing with the most important issues facing the use of biomaterials in clinical practice. The scope of the journal covers the wide range of physical, biological and chemical sciences that underpin the design of biomaterials and the clinical disciplines in which they are used. These sciences include polymer synthesis and characterization, drug and gene vector design, the biology of the host response, immunology and toxicology and self assembly at the nanoscale. Clinical applications include the therapies of medical technology and regenerative medicine in all clinical disciplines, and diagnostic systems that reply on innovative contrast and sensing agents. The journal is relevant to areas such as cancer diagnosis and therapy, implantable devices, drug delivery systems, gene vectors, bionanotechnology and tissue engineering.