1
|
Puistola P, Miettinen S, Skottman H, Mörö A. Novel strategy for multi-material 3D bioprinting of human stem cell based corneal stroma with heterogenous design. Mater Today Bio 2024; 24:100924. [PMID: 38226015 PMCID: PMC10788621 DOI: 10.1016/j.mtbio.2023.100924] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2023] [Revised: 12/13/2023] [Accepted: 12/18/2023] [Indexed: 01/17/2024] Open
Abstract
Three-dimensional (3D) bioprinting offers an automated, customizable solution to manufacture highly detailed 3D tissue constructs and holds great promise for regenerative medicine to solve the severe global shortage of donor tissues and organs. However, uni-material 3D bioprinting is not sufficient for manufacturing heterogenous 3D constructs with native-like microstructures and thus, innovative multi-material solutions are required. Here, we developed a novel multi-material 3D bioprinting strategy for bioprinting human corneal stroma. The human cornea is the transparent outer layer of your eye, and vision loss due to corneal blindness has serious effects on the quality of life of individuals. One of the main reasons for corneal blindness is the damage in the detailed organization of the corneal stroma where collagen fibrils are arranged in layers perpendicular to each other and the corneal stromal cells grow along the fibrils. Donor corneas for treating corneal blindness are scarce, and the current tissue engineering (TE) technologies cannot produce artificial corneas with the complex microstructure of native corneal stroma. To address this, we developed a novel multi-material 3D bioprinting strategy to mimic detailed organization of corneal stroma. These multi-material 3D structures with heterogenous design were bioprinted by using human adipose tissue -derived stem cells (hASCs) and hyaluronic acid (HA) -based bioinks with varying stiffnesses. In our novel design of 3D models, acellular stiffer HA-bioink and cell-laden softer HA-bioink were printed in alternating filaments, and the filaments were printed perpendicularly in alternating layers. The multi-material bioprinting strategy was applied for the first time in corneal stroma 3D bioprinting to mimic the native microstructure. As a result, the soft bioink promoted cellular growth and tissue formation of hASCs in the multi-material 3D bioprinted composites, whereas the stiff bioink provided mechanical support as well as guidance of cellular organization upon culture. Interestingly, cellular growth and tissue formation altered the mechanical properties of the bioprinted composite constructs significantly. Importantly, the bioprinted composite structures showed good integration to the host tissue in ex vivo cornea organ culture model. As a conclusion, the developed multi-material bioprinting strategy provides great potential as a biofabrication solution for manufacturing organized, heterogenous microstructures of native tissues. To the best of our knowledge, this multi-material bioprinting strategy has never been applied in corneal bioprinting. Therefore, our work advances the technological achievements in additive manufacturing and brings the field of corneal TE to a new level.
Collapse
Affiliation(s)
- Paula Puistola
- Eye Regeneration Group, Faculty of Medicine and Health Technology, Tampere University, Tampere 33520, Finland
| | - Susanna Miettinen
- Adult Stem Cell Group, Faculty of Medicine and Health Technology, Tampere University, Tampere 33520, Finland
- Research, Development and Innovation Centre, Tampere University Hospital, 33520 Tampere, Finland
| | - Heli Skottman
- Eye Regeneration Group, Faculty of Medicine and Health Technology, Tampere University, Tampere 33520, Finland
| | - Anni Mörö
- Eye Regeneration Group, Faculty of Medicine and Health Technology, Tampere University, Tampere 33520, Finland
| |
Collapse
|
2
|
Montalvo-Parra MD, Ortega-Lara W, Loya-García D, Bustamante-Arias A, Guerrero-Ramírez GI, Calzada-Rodríguez CE, Torres-Guerrero GF, Hernández-Sedas B, Cárdenas-Rodríguez IT, Guevara-Quintanilla SE, Salán-Gomez M, Hernández-Delgado MÁ, Garza-González S, Gamboa-Quintanilla MG, Villagómez-Valdez LG, Zavala J, Valdez-García JE. Customizable Collagen Vitrigel Membranes and Preliminary Results in Corneal Engineering. Polymers (Basel) 2022; 14:polym14173556. [PMID: 36080636 PMCID: PMC9460691 DOI: 10.3390/polym14173556] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2022] [Revised: 07/28/2022] [Accepted: 08/24/2022] [Indexed: 11/16/2022] Open
Abstract
Corneal opacities are a leading cause of visual impairment that affect 4.2 million people annually. The current treatment is corneal transplantation, which is limited by tissue donor shortages. Corneal engineering aims to develop membranes that function as scaffolds in corneal cell transplantation. Here, we describe a method for producing transplantable corneal constructs based on a collagen vitrigel (CVM) membrane and corneal endothelial cells (CECs). The CVMs were produced using increasing volumes of collagen type I: 1X (2.8 μL/mm2), 2X, and 3X. The vitrification process was performed at 40% relative humidity (RH) and 40 °C using a matryoshka-like system consisting of a shaking-oven harboring a desiccator with a saturated K2CO3 solution. The CVMs were characterized via SEM microscopy, cell adherence, FTIR, and manipulation in an ex vivo model. A pilot transplantation of the CECs/CVM construct in rabbits was also carried out. The thickness of the CVMs was 3.65–7.2 µm. The transparency was superior to a human cornea (92.6% = 1X; 94% = 2X; 89.21% = 3X). SEM microscopy showed a homogenous surface and laminar organization. The cell concentration seeded over the CVM increased threefold with no significant difference between 1X, 2X, and 3X (p = 0.323). The 2X-CVM was suitable for surgical manipulation in the ex vivo model. Constructs using the CECs/2X-CVM promoted corneal transparency restoration.
Collapse
Affiliation(s)
- María Dolores Montalvo-Parra
- Tecnologico de Monterrey, Escuela de Ingenieria, 2501 Garza Sada Ave., Colonia Tecnologico. C.P., 64849 Monterrey, NL, Mexico
- Tecnologico de Monterrey, Escuela de Medicina, 3000 Morones Prieto Ave., Colonia Los Doctores. C.P., 64710 Monterrey, NL, Mexico
| | - Wendy Ortega-Lara
- Tecnologico de Monterrey, Escuela de Ingenieria, 2501 Garza Sada Ave., Colonia Tecnologico. C.P., 64849 Monterrey, NL, Mexico
| | - Denise Loya-García
- Tecnologico de Monterrey, Escuela de Medicina, 3000 Morones Prieto Ave., Colonia Los Doctores. C.P., 64710 Monterrey, NL, Mexico
| | - Andrés Bustamante-Arias
- Tecnologico de Monterrey, Escuela de Medicina, 3000 Morones Prieto Ave., Colonia Los Doctores. C.P., 64710 Monterrey, NL, Mexico
| | - Guillermo-Isaac Guerrero-Ramírez
- Tecnologico de Monterrey, Escuela de Medicina, 3000 Morones Prieto Ave., Colonia Los Doctores. C.P., 64710 Monterrey, NL, Mexico
| | - Cesar E. Calzada-Rodríguez
- Tecnologico de Monterrey, Escuela de Medicina, 3000 Morones Prieto Ave., Colonia Los Doctores. C.P., 64710 Monterrey, NL, Mexico
| | - Guiomar Farid Torres-Guerrero
- Tecnologico de Monterrey, Escuela de Medicina, 3000 Morones Prieto Ave., Colonia Los Doctores. C.P., 64710 Monterrey, NL, Mexico
| | - Betsabé Hernández-Sedas
- Tecnologico de Monterrey, Escuela de Medicina, 3000 Morones Prieto Ave., Colonia Los Doctores. C.P., 64710 Monterrey, NL, Mexico
| | - Italia Tatnaí Cárdenas-Rodríguez
- Tecnologico de Monterrey, Escuela de Medicina, 3000 Morones Prieto Ave., Colonia Los Doctores. C.P., 64710 Monterrey, NL, Mexico
| | - Sergio E. Guevara-Quintanilla
- Tecnologico de Monterrey, Escuela de Medicina, 3000 Morones Prieto Ave., Colonia Los Doctores. C.P., 64710 Monterrey, NL, Mexico
| | - Marcelo Salán-Gomez
- Tecnologico de Monterrey, Escuela de Medicina, 3000 Morones Prieto Ave., Colonia Los Doctores. C.P., 64710 Monterrey, NL, Mexico
| | - Miguel Ángel Hernández-Delgado
- Tecnologico de Monterrey, Escuela de Medicina, 3000 Morones Prieto Ave., Colonia Los Doctores. C.P., 64710 Monterrey, NL, Mexico
| | - Salvador Garza-González
- Tecnologico de Monterrey, Escuela de Medicina, 3000 Morones Prieto Ave., Colonia Los Doctores. C.P., 64710 Monterrey, NL, Mexico
| | - Mayra G. Gamboa-Quintanilla
- Tecnologico de Monterrey, Escuela de Medicina, 3000 Morones Prieto Ave., Colonia Los Doctores. C.P., 64710 Monterrey, NL, Mexico
| | - Luis Guillermo Villagómez-Valdez
- Tecnologico de Monterrey, Escuela de Medicina, 3000 Morones Prieto Ave., Colonia Los Doctores. C.P., 64710 Monterrey, NL, Mexico
| | - Judith Zavala
- Tecnologico de Monterrey, Escuela de Medicina, 3000 Morones Prieto Ave., Colonia Los Doctores. C.P., 64710 Monterrey, NL, Mexico
- Correspondence:
| | - Jorge E. Valdez-García
- Tecnologico de Monterrey, Escuela de Medicina, 3000 Morones Prieto Ave., Colonia Los Doctores. C.P., 64710 Monterrey, NL, Mexico
| |
Collapse
|
3
|
Seow WY, Kandasamy K, Peh GSL, Mehta JS, Sun W. Ultrathin, Strong, and Cell-Adhesive Agarose-Based Membranes Engineered as Substrates for Corneal Endothelial Cells. ACS Biomater Sci Eng 2019; 5:4067-4076. [DOI: 10.1021/acsbiomaterials.9b00610] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Affiliation(s)
- Wei Yang Seow
- Institute of Bioengineering and Nanotechnology, 31 Biopolis Way, #07-01, Singapore 138669
| | - Karthikeyan Kandasamy
- Institute of Bioengineering and Nanotechnology, 31 Biopolis Way, #07-01, Singapore 138669
| | - Gary S. L. Peh
- Tissue Engineering and Stem Cell Group, Singapore Eye Research Institute, Singapore
- Duke-NUS Graduate Medical School, Singapore
| | - Jodhbir S. Mehta
- Tissue Engineering and Stem Cell Group, Singapore Eye Research Institute, Singapore
- Duke-NUS Graduate Medical School, Singapore
- Singapore National Eye Centre, Singapore
| | - William Sun
- Institute of Bioengineering and Nanotechnology, 31 Biopolis Way, #07-01, Singapore 138669
| |
Collapse
|
4
|
Kim H, Jang J, Park J, Lee KP, Lee S, Lee DM, Kim KH, Kim HK, Cho DW. Shear-induced alignment of collagen fibrils using 3D cell printing for corneal stroma tissue engineering. Biofabrication 2019; 11:035017. [PMID: 30995622 DOI: 10.1088/1758-5090/ab1a8b] [Citation(s) in RCA: 89] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The microenvironments of tissues or organs are complex architectures comprised of structural proteins including collagen. Particularly, the cornea is organized in a lattice pattern of collagen fibrils which play a significant role in its transparency. This paper introduces a transparent bioengineered corneal structure for transplantation. The structure is fabricated by inducing shear stress to a corneal stroma-derived decellularized extracellular matrix bioink based on a 3D cell printing technique. The printed structure recapitulates the native macrostructure of the cornea with aligned collagen fibrils which results in the construction of a highly matured and transparent cornea stroma analog. The level of shear stress, controlled by the various size of the printing nozzle, manipulates the arrangement of the fibrillar structure. With proper parameter selection, the printed cornea exhibits high cellular alignment capability, indicating a tissue-specific structural organization of collagen fibrils. In addition, this structural regulation enhances critical cellular events in the assembly of collagen over time. Interestingly, the collagen fibrils that remodeled along with the printing path create a lattice pattern similar to the structure of native human cornea after 4 weeks in vivo. Taken together, these results establish the possibilities and versatility of fabricating aligned collagen fibrils; this represents significant advances in corneal tissue engineering.
Collapse
Affiliation(s)
- Hyeonji Kim
- Department of Mechanical Engineering, Pohang University of Science and Technology, 77 Cheongam-ro, Pohang, Gyeongbuk, 37673, Republic of Korea
| | | | | | | | | | | | | | | | | |
Collapse
|
5
|
Zeng Y, Fan L, Deng M, Sun P, Zhang B, Zhang Q, Li L, Xu Z. Development of high refractive and high water content polythiourethane/AA hydrogels for potential artificial cornea implants. INT J POLYM MATER PO 2019. [DOI: 10.1080/00914037.2019.1596908] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Affiliation(s)
- Youlan Zeng
- Hubei Collaborative Innovation Center for Advanced Organic Chemical Materials, Ministry of Education Key Laboratory for the Green Preparation and Application of Functional Materials, Hubei Key Laboratory of Polymer Materials, School of Materials Science and Engineering, Hubei University, Wuhan 430062, China
| | - Lu Fan
- College of Chemistry and Chemical Engineering, Hubei University, Wuhan 430062, China
| | - Min Deng
- Hubei Collaborative Innovation Center for Advanced Organic Chemical Materials, Ministry of Education Key Laboratory for the Green Preparation and Application of Functional Materials, Hubei Key Laboratory of Polymer Materials, School of Materials Science and Engineering, Hubei University, Wuhan 430062, China
| | - Peng Sun
- Hubei Collaborative Innovation Center for Advanced Organic Chemical Materials, Ministry of Education Key Laboratory for the Green Preparation and Application of Functional Materials, Hubei Key Laboratory of Polymer Materials, School of Materials Science and Engineering, Hubei University, Wuhan 430062, China
| | - Boxiao Zhang
- Hubei Collaborative Innovation Center for Advanced Organic Chemical Materials, Ministry of Education Key Laboratory for the Green Preparation and Application of Functional Materials, Hubei Key Laboratory of Polymer Materials, School of Materials Science and Engineering, Hubei University, Wuhan 430062, China
| | - Quanyuan Zhang
- Hubei Collaborative Innovation Center for Advanced Organic Chemical Materials, Ministry of Education Key Laboratory for the Green Preparation and Application of Functional Materials, Hubei Key Laboratory of Polymer Materials, School of Materials Science and Engineering, Hubei University, Wuhan 430062, China
| | - Ling Li
- College of Chemistry and Chemical Engineering, Hubei University, Wuhan 430062, China
| | - Zushun Xu
- Hubei Collaborative Innovation Center for Advanced Organic Chemical Materials, Ministry of Education Key Laboratory for the Green Preparation and Application of Functional Materials, Hubei Key Laboratory of Polymer Materials, School of Materials Science and Engineering, Hubei University, Wuhan 430062, China
| |
Collapse
|
6
|
Zhao P, Xu J, Zhang Y, Zhu W, Cui Y. Polymerizable-group capped ZnS nanoparticle for high refractive index inorganic-organic hydrogel contact lens. MATERIALS SCIENCE & ENGINEERING. C, MATERIALS FOR BIOLOGICAL APPLICATIONS 2018; 90:485-493. [PMID: 29853117 DOI: 10.1016/j.msec.2018.04.086] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/18/2017] [Revised: 03/26/2018] [Accepted: 04/28/2018] [Indexed: 02/06/2023]
Abstract
Refractive index (RI) is an important parameter for contact lens biomaterials. In this paper, a novel polymerizable-group capped ZnS nanoparticle (NP) was synthesized by chemical link between hydroxyl group on the surface of ZnS (ME-capped) and isocyanate group of polymerizable molecule of 2-isocyanatoethyl methacrylate. Then the ZnS NP copolymerized with monomer of 2-hydroxyethyl methacrylate (HEMA) and N,N-dimethylacrylamide (DMA) to prepare high refractive index hydrogel contact lens with high content of inorganic ZnS NP. Increasing polymerizable-group capped ZnS content in the hydrogels improved its RI value and mechanical properties, however decreased slightly its transmittance, equilibrium (ESR) and lysozyme deposition on the hydrogel surface. The ZnS-containing hydrogels possessed good cytocompatibility and in vivo biocompatibility in rabbit eyes, demonstrating a potential application as high RI ocular refractive correction biomaterial.
Collapse
Affiliation(s)
- Peili Zhao
- Shandong Provincial Key Laboratory of Fine Chemical, School of Chemistry and Pharmaceutical Engineering, Qilu University of Technology (Shandong Academy of Sciences), Jinan 250353, China
| | - Jinku Xu
- Shandong Provincial Key Laboratory of Fine Chemical, School of Chemistry and Pharmaceutical Engineering, Qilu University of Technology (Shandong Academy of Sciences), Jinan 250353, China.
| | - Yongchun Zhang
- Shandong Provincial Key Laboratory of Fine Chemical, School of Chemistry and Pharmaceutical Engineering, Qilu University of Technology (Shandong Academy of Sciences), Jinan 250353, China
| | - Weiyue Zhu
- Shandong Provincial Key Laboratory of Fine Chemical, School of Chemistry and Pharmaceutical Engineering, Qilu University of Technology (Shandong Academy of Sciences), Jinan 250353, China
| | - Yuezhi Cui
- Shandong Provincial Key Laboratory of Fine Chemical, School of Chemistry and Pharmaceutical Engineering, Qilu University of Technology (Shandong Academy of Sciences), Jinan 250353, China
| |
Collapse
|
7
|
Gouveia RM, González-Andrades E, Cardona JC, González-Gallardo C, Ionescu AM, Garzon I, Alaminos M, González-Andrades M, Connon CJ. Controlling the 3D architecture of Self-Lifting Auto-generated Tissue Equivalents (SLATEs) for optimized corneal graft composition and stability. Biomaterials 2017; 121:205-219. [PMID: 28092777 PMCID: PMC5267636 DOI: 10.1016/j.biomaterials.2016.12.023] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2016] [Revised: 12/02/2016] [Accepted: 12/21/2016] [Indexed: 12/26/2022]
Abstract
Ideally, biomaterials designed to play specific physical and physiological roles in vivo should comprise components and microarchitectures analogous to those of the native tissues they intend to replace. For that, implantable biomaterials need to be carefully designed to have the correct structural and compositional properties, which consequently impart their bio-function. In this study, we showed that the control of such properties can be defined from the bottom-up, using smart surface templates to modulate the structure, composition, and bio-mechanics of human transplantable tissues. Using multi-functional peptide amphiphile-coated surfaces with different anisotropies, we were able to control the phenotype of corneal stromal cells and instruct them to fabricate self-lifting tissues that closely emulated the native stromal lamellae of the human cornea. The type and arrangement of the extracellular matrix comprising these corneal stromal Self-Lifting Analogous Tissue Equivalents (SLATEs) were then evaluated in detail, and was shown to correlate with tissue function. Specifically, SLATEs comprising aligned collagen fibrils were shown to be significantly thicker, denser, and more resistant to proteolytic degradation compared to SLATEs formed with randomly-oriented constituents. In addition, SLATEs were highly transparent while providing increased absorption to near-UV radiation. Importantly, corneal stromal SLATEs were capable of constituting tissues with a higher-order complexity, either by creating thicker tissues through stacking or by serving as substrate to support a fully-differentiated, stratified corneal epithelium. SLATEs were also deemed safe as implants in a rabbit corneal model, being capable of integrating with the surrounding host tissue without provoking inflammation, neo-vascularization, or any other signs of rejection after a 9-months follow-up. This work thus paves the way for the de novo bio-fabrication of easy-retrievable, scaffold-free human tissues with controlled structural, compositional, and functional properties to replace corneal, as well as other, tissues.
Collapse
Affiliation(s)
- Ricardo M Gouveia
- Institute of Genetic Medicine, Newcastle University, International Centre for Life, Newcastle-upon-Tyne, UK
| | - Elena González-Andrades
- Tissue Engineering Group, Department of Histology, Faculty of Medicine and Dentistry, University of Granada, Granada, Spain
| | - Juan C Cardona
- Laboratory of Biomaterials and Optics, Optics Department, Faculty of Sciences, University of Granada, Granada, Spain
| | | | - Ana M Ionescu
- Laboratory of Biomaterials and Optics, Optics Department, Faculty of Sciences, University of Granada, Granada, Spain
| | - Ingrid Garzon
- Tissue Engineering Group, Department of Histology, Faculty of Medicine and Dentistry, University of Granada, Granada, Spain
| | - Miguel Alaminos
- Tissue Engineering Group, Department of Histology, Faculty of Medicine and Dentistry, University of Granada, Granada, Spain
| | - Miguel González-Andrades
- Schepens Eye Research Institute and Massachusetts Eye and Ear, Department of Ophthalmology, Harvard Medical School, Boston, MA, USA.
| | - Che J Connon
- Institute of Genetic Medicine, Newcastle University, International Centre for Life, Newcastle-upon-Tyne, UK.
| |
Collapse
|
8
|
Hariya T, Tanaka Y, Yokokura S, Nakazawa T. Transparent, resilient human amniotic membrane laminates for corneal transplantation. Biomaterials 2016; 101:76-85. [DOI: 10.1016/j.biomaterials.2016.05.038] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2016] [Accepted: 05/24/2016] [Indexed: 10/21/2022]
|
9
|
Ghezzi CE, Rnjak-Kovacina J, Kaplan DL. Corneal tissue engineering: recent advances and future perspectives. TISSUE ENGINEERING PART B-REVIEWS 2015; 21:278-87. [PMID: 25434371 DOI: 10.1089/ten.teb.2014.0397] [Citation(s) in RCA: 115] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
To address the growing need for corneal transplants two main approaches are being pursued: allogenic and synthetic materials. Allogenic tissue from human donors is currently the preferred choice; however, there is a worldwide shortage in donated corneal tissue. In addition, tissue rejection often limits the long-term success of this approach. Alternatively, synthetic homologs to donor corneal grafts are primarily considered temporary replacements until suitable donor tissue becomes available, as they result in a high incidence of graft failure. Tissue engineered cornea analogs would provide effective cornea tissue substitutes and alternatives to address the need to reduce animal testing of commercial products. Recent progress toward these needs is reviewed here, along with future perspectives.
Collapse
Affiliation(s)
- Chiara E Ghezzi
- 1Department of Biomedical Engineering, Tufts University, Medford, Massachusetts
| | - Jelena Rnjak-Kovacina
- 1Department of Biomedical Engineering, Tufts University, Medford, Massachusetts.,2Graduate School of Biomedical Engineering, UNSW Australia, Sydney, Australia
| | - David L Kaplan
- 1Department of Biomedical Engineering, Tufts University, Medford, Massachusetts
| |
Collapse
|
10
|
Koulikovska M, Rafat M, Petrovski G, Veréb Z, Akhtar S, Fagerholm P, Lagali N. Enhanced regeneration of corneal tissue via a bioengineered collagen construct implanted by a nondisruptive surgical technique. Tissue Eng Part A 2015; 21:1116-30. [PMID: 25412075 DOI: 10.1089/ten.tea.2014.0562] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Severe shortage of donor corneas for transplantation, particularly in developing countries, has prompted the advancement of bioengineered tissue alternatives. Bioengineered corneas that can withstand transplantation while maintaining transparency and compatibility with host cells, and that are additionally amenable to standardized low-cost mass production are sought. In this study, a bioengineered porcine construct (BPC) was developed to function as a biodegradable scaffold to promote corneal stromal regeneration by host cells. Using high-purity medical-grade type I collagen, high 18% collagen content and optimized EDC-NHS cross-linker ratio, BPCs were fabricated into hydrogel corneal implants with over 90% transparency and four-fold increase in strength and stiffness compared with previous versions. Remarkably, optical transparency was achieved despite the absence of collagen fibril organization at the nanoscale. In vitro testing indicated that BPC supported confluent human epithelial and stromal-derived mesenchymal stem cell populations. With a novel femtosecond laser-assisted corneal surgical model in rabbits, cell-free BPCs were implanted in vivo in the corneal stroma of 10 rabbits over an 8-week period. In vivo, transparency of implanted corneas was maintained throughout the postoperative period, while healing occurred rapidly without inflammation and without the use of postoperative steroids. BPC implants had a 100% retention rate at 8 weeks, when host stromal cells began to migrate into implants. Direct histochemical evidence of stromal tissue regeneration was observed by means of migrated host cells producing new collagen from within the implants. This study indicates that a cost-effective BPC extracellular matrix equivalent can incorporate cells passively to initiate regenerative healing of the corneal stroma, and is compatible with human stem or organ-specific cells for future therapeutic applications as a stromal replacement for treating blinding disorders of the cornea.
Collapse
|
11
|
Zhang C, Wen J, Yan J, Kao Y, Ni Z, Cui X, Wang H. In situ growth induction of the corneal stroma cells using uniaxially aligned composite fibrous scaffolds. RSC Adv 2015. [DOI: 10.1039/c4ra16609d] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
An electrospun fibrous scaffold was fabricated and used in the in situ remediation of rabbits’ corneal stromata.
Collapse
Affiliation(s)
- Cong Zhang
- College of Chemistry
- Jilin University
- Changchun 130012
- P. R. China
| | - Jihong Wen
- Department of Jilin University
- First Clinical Hospital of Bethune Medical
- Changchun 130012
- P. R. China
| | - Jing Yan
- Department of Chemistry and Biochemistry Nanocenter
- University of South Carolina
- Columbia
- USA
| | - Yanbing Kao
- Clinic College of Medicine
- Jilin University
- Changchun 130012
- P. R. China
| | - Zhiqiang Ni
- Department of Tumor Biological Therapy Jilin Province People’s Hospital
- Changchun 130012
- P. R. China
| | - Xuejun Cui
- College of Chemistry
- Jilin University
- Changchun 130012
- P. R. China
| | - Hongyan Wang
- College of Chemistry
- Jilin University
- Changchun 130012
- P. R. China
| |
Collapse
|
12
|
Petsch C, Schlötzer-Schrehardt U, Meyer-Blazejewska E, Frey M, Kruse FE, Bachmann BO. Novel collagen membranes for the reconstruction of the corneal surface. Tissue Eng Part A 2014; 20:2378-89. [PMID: 24621144 DOI: 10.1089/ten.tea.2013.0552] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
No standardized biomaterial exists for the surgical treatment of persistent corneal erosions and ulcerations. We analyzed the suitability and biocompatibility of defined noncross-linked and UV/riboflavin cross-linked equine type I collagen membranes for the reconstruction of the corneal surface. Isolated human oral mucosa epithelial cells, a cell type in clinical use for the treatment of ocular surface diseases, were subcultivated on both types of membranes and examined concerning cell adhesion, proliferation, and differentiation. Biocompatibility was evaluated following superficial and intrastromal corneal transplantation in New Zealand white rabbits. In cell cultures all collagen membranes supported adhesion of oral mucosa epithelial cells leading to the formation of multilayered epithelial cell sheets. After intrastromal corneal implantation clinical signs of degradation were seen in all variants of collagen membranes, which was fastest in noncross-linked variants. The histological and ultrastructural level invasion of keratocytes and production of new collagen fibers inside the collagen membranes could be detected in noncross-linked variants. After superficial corneal implantation covering of the membranes by corneal epithelium over time was visible. Ultrastructural analysis showed a slower rate of degradation and less invading keratocytes in cross-linked variants compared with noncross-linked collagen membranes. Cross-linked and noncross-linked variants of the collagen membrane proofed to be suitable to serve as a carrier for epithelial stem cells in vitro and showed a high biocompatibility in vivo. These results indicate that the tested collagen membranes might be suitable for the reconstruction of the corneal surface in patients with nonhealing ulcerations. Whether membranes with faster or slower degradation properties are preferable for the treatment of persistent corneal ulcerations might depend on the underlying corneal pathology and the degree of concomitant inflammation.
Collapse
Affiliation(s)
- Corinna Petsch
- 1 Department of Ophthalmology, University of Erlangen-Nürnberg , Erlangen, Germany
| | | | | | | | | | | |
Collapse
|
13
|
Takiyama N, Mizuno T, Iwai R, Uechi M, Nakayama Y. In-body tissue-engineered collagenous connective tissue membranes (BIOSHEETs) for potential corneal stromal substitution. J Tissue Eng Regen Med 2013; 10:E518-E526. [PMID: 24668614 DOI: 10.1002/term.1859] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2013] [Revised: 09/07/2013] [Accepted: 11/10/2013] [Indexed: 01/15/2023]
Abstract
There is a severe shortage of donor cornea for transplantation in many countries. Collagenous connective tissue membranes, named BIOSHEETs, grown in vivo were successfully implanted in rabbit corneal stroma for in vivo evaluation of their suitability as a corneal stromal substitute to solve this global donor shortage. BIOSHEETs were prepared by embedding silicone moulds into dorsal subcutaneous pouches in rabbits for 1 month and stored in glycerol. After re-swelling in saline and trephining, disk-shaped BIOSHEETs (4 mm diameter) were allogeneically implanted into stromal pockets prepared in the right cornea of seven rabbits. Clinical tests for corneal thickness and transparency, and tissue analyses were performed. Because the BIOSHEETs (thickness, 131 ± 14 µm) obtained were opaque immediately after implantation, the transparency of the cornea decreased. The total thickness of the BIOSHEET-implanted cornea increased from 364 ± 21.0 µm to 726 ± 131 µm. After 4 weeks' implantation, the thickness of the cornea stabilized (493 ± 80 µm at 4 weeks and 447 ± 46 µm at 8 weeks). The transparency of the cornea increased progressively with time of implantation. The random orientation of collagen fibrils in the original BIOSHEETs tended to be homogeneous, similar to that of the native stroma. No inflammatory cells accumulated and fibroblast-like cells infiltrated the implant. The BIOSHEETs showed high biocompatibility with stromal tissues; however, further studies are needed to test its functional aspects. Although this research is only intended as a proof of concept, BIOSHEETs may be considered a feasible corneal stromal replacement, especially for treating visual impairment caused by stromal haze. Copyright © 2013 John Wiley & Sons, Ltd.
Collapse
Affiliation(s)
- Naoaki Takiyama
- Department of Veterinary Medicine, College of Bioresource Sciences, Nihon University, Kanagawa, Japan
| | - Takeshi Mizuno
- Department of Veterinary Medicine, College of Bioresource Sciences, Nihon University, Kanagawa, Japan.,Division of Medical Engineering and Materials, National Cerebral and Cardiovascular Centre Research Institute, Osaka, Japan
| | - Ryosuke Iwai
- Division of Medical Engineering and Materials, National Cerebral and Cardiovascular Centre Research Institute, Osaka, Japan
| | - Masami Uechi
- Department of Veterinary Medicine, College of Bioresource Sciences, Nihon University, Kanagawa, Japan.,Division of Medical Engineering and Materials, National Cerebral and Cardiovascular Centre Research Institute, Osaka, Japan
| | - Yasuhide Nakayama
- Division of Medical Engineering and Materials, National Cerebral and Cardiovascular Centre Research Institute, Osaka, Japan.
| |
Collapse
|
14
|
Luo H, Lu Y, Wu T, Zhang M, Zhang Y, Jin Y. Construction of tissue-engineered cornea composed of amniotic epithelial cells and acellular porcine cornea for treating corneal alkali burn. Biomaterials 2013; 34:6748-59. [DOI: 10.1016/j.biomaterials.2013.05.045] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2013] [Accepted: 05/23/2013] [Indexed: 01/03/2023]
|
15
|
Zhang Q, Fang Z, Cao Y, Du H, Wu H, Beuerman R, Chan-Park MB, Duan H, Xu R. High Refractive Index Inorganic-Organic Interpenetrating Polymer Network (IPN) Hydrogel Nanocomposite toward Artificial Cornea Implants. ACS Macro Lett 2012; 1:876-881. [PMID: 35607136 DOI: 10.1021/mz300078y] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The use of artificial cornea implants has received increasing attention for treating cornea-related diseases and vision errors due to the low side effects. To achieve long-term successful vision correction, stable and biocompatible materials of high refractive index (RI) need to be developed. Herein, we developed an interpenetrating polymer network (IPN) hydrogel containing well-dispersed ZnS nanoparticles (∼3 nm) covalently linked to the first polymer network, poly(2-hydroethyl methacrylate) (PHEMA). The second polymer network used was poly(acrylic acid) (PAA). The resultant ZnS/PHEMA/PAA IPN nanocomposite is clear and transparent at both dry and hydrated states with their RIs measured to be as high as 1.65 and 1.49, respectively. The equilibrium water content of the hydrogel nanocomposite reached 60.2% which is reasonably near to that of cornea. The material exerted minimal cytotoxicity toward primary epidermal keratinocyte cells. The high RI IPN hydrogel nanocomposite developed here might be an excellent candidate for artificial cornea implants.
Collapse
Affiliation(s)
- Quanyuan Zhang
- School of Chemical & Biomedical Engineering, Nanyang Technological University, N1.2, 62 Nanyang Drive, Singapore 637459
| | - Zheng Fang
- School of Chemical & Biomedical Engineering, Nanyang Technological University, N1.2, 62 Nanyang Drive, Singapore 637459
| | - Ye Cao
- School of Chemical & Biomedical Engineering, Nanyang Technological University, N1.2, 62 Nanyang Drive, Singapore 637459
| | - Huamao Du
- School of Chemical & Biomedical Engineering, Nanyang Technological University, N1.2, 62 Nanyang Drive, Singapore 637459
| | - Hong Wu
- Department of Ophthalmology, Second Hospital of Jilin University, Changchun, China
130041
| | - Roger Beuerman
- Singapore Eye Research Institute, 11 Third Hospital Ave 168751, Singapore 6223
8458
| | - Mary B. Chan-Park
- School of Chemical & Biomedical Engineering, Nanyang Technological University, N1.2, 62 Nanyang Drive, Singapore 637459
| | - Hongwei Duan
- School of Chemical & Biomedical Engineering, Nanyang Technological University, N1.2, 62 Nanyang Drive, Singapore 637459
| | - Rong Xu
- School of Chemical & Biomedical Engineering, Nanyang Technological University, N1.2, 62 Nanyang Drive, Singapore 637459
| |
Collapse
|
16
|
Tanaka Y, Kubota A, Yokokura S, Uematsu M, Shi D, Yamato M, Okano T, Quantock AJ, Nishida K. Optical mechanical refinement of human amniotic membrane by dehydration and cross-linking. J Tissue Eng Regen Med 2012; 6:731-7. [DOI: 10.1002/term.479] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2010] [Revised: 05/07/2011] [Accepted: 07/11/2011] [Indexed: 11/07/2022]
Affiliation(s)
| | - Akira Kubota
- Department of Ophthalmology and Visual Science; Tohoku University Graduate School of Medicine; Sendai; Miyagi; Japan
| | - Shunji Yokokura
- Department of Ophthalmology and Visual Science; Tohoku University Graduate School of Medicine; Sendai; Miyagi; Japan
| | | | | | - Masayuki Yamato
- Institute of Advanced Biomedical Engineering and Science Tokyo Women's Medical University (TWIns); Shinjuku-ku; Tokyo; Japan
| | - Teruo Okano
- Institute of Advanced Biomedical Engineering and Science Tokyo Women's Medical University (TWIns); Shinjuku-ku; Tokyo; Japan
| | - Andrew J. Quantock
- School of Optometry and Vision Sciences; Cardiff University; Cardiff; United Kingdom
| | | |
Collapse
|
17
|
Isobe Y, Kosaka T, Kuwahara G, Mikami H, Saku T, Kodama S. Oriented Collagen Scaffolds for Tissue Engineering. MATERIALS 2012; 5:501-511. [PMID: 28817059 PMCID: PMC5448924 DOI: 10.3390/ma5030501] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/25/2012] [Revised: 03/06/2012] [Accepted: 03/08/2012] [Indexed: 11/16/2022]
Abstract
Oriented collagen scaffolds were developed in the form of sheet, mesh and tube by arraying flow-oriented collagen string gels and dehydrating the arrayed gels. The developed collagen scaffolds can be any practical size with any direction of orientation for tissue engineering applications. The birefringence of the collagen scaffolds was quantitatively analyzed by parallel Nicols method. Since native collagen in the human body has orientations such as bone, cartilage, tendon and cornea, and the orientation has a special role for the function of human organs, the developed various types of three-dimensional oriented collagen scaffolds are expected to be useful biomaterials for tissue engineering and regenerative medicines.
Collapse
Affiliation(s)
- Yoshihiro Isobe
- Atree Inc., 16-12-1 Hiroo Shibuya-ku, Tokyo, 150-0012, Japan.
| | - Toru Kosaka
- Atree Inc., 16-12-1 Hiroo Shibuya-ku, Tokyo, 150-0012, Japan.
| | - Go Kuwahara
- Department of Regenerative Medicine & Transplantation, Faculty of Medicine, Fukuoka University, 7-45-1, Nanakuma, Jonan-ku, Fukuoka City, Fukuoka Pref, 814-0133, Japan.
| | - Hiroshi Mikami
- Department of Regenerative Medicine & Transplantation, Faculty of Medicine, Fukuoka University, 7-45-1, Nanakuma, Jonan-ku, Fukuoka City, Fukuoka Pref, 814-0133, Japan.
| | - Taro Saku
- Atree Inc., 16-12-1 Hiroo Shibuya-ku, Tokyo, 150-0012, Japan.
| | - Shohta Kodama
- Department of Regenerative Medicine & Transplantation, Faculty of Medicine, Fukuoka University, 7-45-1, Nanakuma, Jonan-ku, Fukuoka City, Fukuoka Pref, 814-0133, Japan.
| |
Collapse
|
18
|
Zhang X, Nakahara Y, Xuan D, Wu D, Zhao FK, Li XY, Zhang JS. Study on the optical property and biocompatibility of a tissue engineering cornea. Int J Ophthalmol 2012; 5:45-9. [PMID: 22553753 DOI: 10.3980/j.issn.2222-3959.2012.01.09] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2011] [Accepted: 02/03/2012] [Indexed: 01/08/2023] Open
Abstract
AIM To study the optical property and biocompatibility of a tissue engineering cornea. METHODS : The cross-linker of N-(3-Dimethylaminoropyl)-N'ethylcarbodiimide hydrochloride (EDC)/N-Hydroxysuccinimide (NHS) was mixed with Type I collagen at 10% (weight/volume). The final solution was molded to the shape of a corneal contact lens. The collagen concentrations of 10%, 12.5%, 15%, 17.5% and 20% artificial corneas were tested by UV/vis-spectroscopy for their transparency compared with normal rat cornea. 10-0 sutures were knotted on the edges of substitute to measure the corneal buttons's mechanical properties. Normal rat corneal tissue primary culture on the collagen scaffold was observed in 4 weeks. Histopathologic examinations were performed after 4 weeks of in vitro culturing. RESULTS The collagen scaffold appearance was similar to that of soft contact lens. With the increase of collagen concentration, the transparency of artificial corneal buttons was diminished, but the toughness of the scaffold was enhanced. The scaffold transparency in the 10% concentration collagen group resembled normal rat cornea. To knot and embed the scaffold under the microscope, 20% concentration collagen group was more effective during implantation than lower concentrations of collagen group. In the first 3 weeks, corneal cell proliferation was highly active. The shapes of cells that grew on the substitute had no significant difference when compared with the cells before they were moved to the scaffold. However, on the fortieth day, most cells detached from the scaffold and died. Histopathologic examination of the primary culture scaffold revealed well grown corneal cells tightly attached to the scaffold in the former culturing. CONCLUSION Collagen scaffold can be molded to the shape of soft contact corneal lens with NHS/EDC. The biological stability and biocompatibility of collagen from animal species may be used as material in preparing to engineer artificial corneal scaffold.
Collapse
Affiliation(s)
- Xu Zhang
- Department of Ophthalmology, the Fourth Affiliated Hospital of China Medical University, Eye Hospital of China Medical University, Provincial Key Laboratory of Lens Research, Shenyang 110005, Liaoning Province, China
| | | | | | | | | | | | | |
Collapse
|
19
|
Oelker AM, Grinstaff MW. Synthesis, characterization, and in vitro evaluation of a hydrogel-based corneal onlay. IEEE Trans Nanobioscience 2011; 11:37-45. [PMID: 21908258 DOI: 10.1109/tnb.2011.2166978] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Blindness due to opacity of the cornea is treated by corneal transplantation with donor tissue. Due to the limited supply of suitable donor corneas, the need for synthetic corneal equivalents is clear. Herein we report the design and in vitro characterization of a hydrogel-based implant; this implant will serve as a permanent, transparent, space-filling onlay with a two-layer design that mimics the native corneal stratification to support surface epithelialization and foster integration with the surrounding tissue. The top layer of the implant was composed of a 2-hydroxyethylmethacrylate hydrogel containing methacrylic acid as the co-monomer (HEMA-co-MAA) with tunable dimensions and compressive modulus ranging from 700-1000 kPa. The bottom layer, which constitutes the bulk of the implant and is designed to provide integration with the corneal stroma, is a dendrimer hydrogel with high water content and compressive modulus ranging from 500-1200 kPa. Both hydrogels were found to possess optical and diffusion properties similar to those of the human cornea. In addition, composite implants with uniform and structurally sound interfaces were formed when the gels were sequentially injected and cross-linked in the same mold. HEMA-co-MAA hydrogels were covalently modified with type I collagen to enable corneal epithelial cell adhesion and spreading that was dependent upon the collagen coating density but independent of hydrogel stiffness. Similarly, dendrimer hydrogels supported the adhesion and spreading of corneal fibroblasts upon modification with the adhesion ligand arginine-glycine-aspartic acid (RGD). Fibroblast adhesion was not dependent upon dendrimer hydrogel stiffness for the formulations studied and, after in vitro culture for 4 weeks, fibroblasts remained able to adhere to and conformally coat the hydrogel surface. In conclusion, the tunable physical properties and structural integrity of the laminated interface suggests that this design is suitable for further study. The judicious tuning of material properties and inclusion of bioactive moieties is a promising strategy for promotion of implant epithelialization and tissue integration.
Collapse
|
20
|
Irreversible optical clearing of rabbit dermis for autogenic corneal stroma transplantation. Biomaterials 2011; 32:6764-72. [PMID: 21715003 DOI: 10.1016/j.biomaterials.2011.05.081] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2011] [Accepted: 05/27/2011] [Indexed: 11/23/2022]
Abstract
Tissue engineering and transplantation of autogenic grafts have been widely investigated for solving problems on current allograft treatments (i.g., donor shortage and rejection). However, it is difficult to obtain an autogenic corneal stromal replacement that is composed of transparent, tough, and thick collagen constructs by current cell culture-based tissue engineering. Aim of this study is to develop transparent dermis for an autogenic corneal stroma transplantation. This study examined dehydration at 4-8°C and carbodiimide cross-linking on cloudy rabbit dermis (approx. 1.8%-3.8% light transmittance at 550 nm) for dermis optical clearing. Transparency of dehydrated rabbit dermis was founded to be approx. 37.9%-41.4% at 550 nm. Additional cross-linking treatment on dehydrated dermis prevented from swelling and clouding in saline, and improved its transparency to be 56.9% at 550 nm. Rabbit corneal epithelium was found to regenerate on optically cleared dermis in vitro. Furthermore, no abnormal biological response (i.e., inflammation, vascularization, and the barrier defect of epithelia) or no optical functional change on optically cleared dermis was observed during its 4-week autogenic transplantation into rabbit corneal stromal pocket.
Collapse
|
21
|
Tanaka Y, Baba K, Duncan TJ, Kubota A, Asahi T, Quantock AJ, Yamato M, Okano T, Nishida K. Transparent, tough collagen laminates prepared by oriented flow casting, multi-cyclic vitrification and chemical cross-linking. Biomaterials 2011; 32:3358-66. [DOI: 10.1016/j.biomaterials.2010.11.011] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2010] [Accepted: 11/06/2010] [Indexed: 10/18/2022]
|
22
|
Irreversible optical clearing of sclera by dehydration and cross-linking. Biomaterials 2010; 32:1080-90. [PMID: 21055804 DOI: 10.1016/j.biomaterials.2010.10.002] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2010] [Accepted: 10/01/2010] [Indexed: 11/20/2022]
Abstract
This study manipulates both clear cornea and opaque sclera by two dehydration processes for revealing the relationship between altered tissue structures and change in optical functions. In contrast to the high levels of light scattering in dehydrated tissues by critical point dry, a simple dehydration at 4-8 °C effectively and significantly improved their visible-light transmission, even in the sclera, with accompanying dense fiber packing. Further improvement in visible-light transmission, from 40-50% to 80-90%, has been achieved by flatting tissue surface with cover glasses during dehydration at low temperature. Such optical clearing of sclera by dehydration is reversible. However, chemical cross-linking effectively stabilizes their densely packed microscopic structures and visible-light transmission at over 50% irreversibly, even at wet conditions. Interestingly, the repetition of both low temperature dehydration/cross-linking treatments effectively reduced the required amounts of cross-linking reagents to keep a high transparency. Wet transparent cross-linked sclera can also show a characteristic strong tensile strength. Furthermore, rabbit corneal epithelium has regenerated on the transparent sclera with cross-linking in vitro.
Collapse
|