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D. Myung, W. Koh, N. Farooqui, J. Ko, J. Noolandi, M. Carrasco, C.W. Frank, C.N. Ta; Development of a Hydrogel Corneal Onlay: Molecular Design and Biological Response . Invest. Ophthalmol. Vis. Sci. 2006;47(13):3931.
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© ARVO (1962-2015); The Authors (2016-present)
The development, characterization, and optimization of a transparent biopolymer for application as a corneal onlay with a high level of nutrient permeability and the capacity for surface epithelialization.
Double network hydrogels were synthesized by two–step polymerization of poly(ethylene glycol) (PEG) and poly(acrylic acid) (PAA) hydrogels. The mesh sizes of the gels were determined through equilibrium swelling measurements. The tensile strength and modulus of each material were determined by strip extensometry, while the diffusion coefficient was determined by measurement of glucose flux. A photoreactive chemical linker was then used to modify the hydrogel surfaces with collagen type I. X–ray photoelectron spectroscopy (XPS) and quantitative amino acid analysis were used to confirm the success of the modification. Primary corneal epithelial cells (CECs) were seeded on the gels to determine the efficacy of the surface modifications. Finally, the hydrogels were implanted into live rabbit corneas using a corneal onlay technique to test for biocompatibility and surface epithelialization.
The hydrogels contained 60–90% water, with glucose diffusion coefficients on the order of 1.0 E –6 cm2/sec, mesh sizes between 20 – 30 Angstroms, and tensile strength greater than 1 MPa. Correlation of mesh size to tensile strength and permeability identified the optimum PEG/PAA system for use subsequent studies. XPS and amino acid analysis of the hydrogel surfaces demonstrated successful modification with collagen. CECs expressing cytokeratin 3 were found to adhere and grow to confluence on hydrogels. Implanted in vivo, the hydrogels remained optically clear and promoted surface epithelialization after 14 days.
Surface–modified PEG/PAA double networks are promising materials for the development of a corneal onlay due to their transparency, biocompatibility, permeability, and capacity for surface epithelialization.
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