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Young-tae Kim, Chetan Bhuwania, SaiSirisha Dhavala; Engineering enabled biomimetic corneal stroma. Invest. Ophthalmol. Vis. Sci. 2012;53(14):3648.
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Limited availability of donor corneas has never been able to match the demand. Thus there is an increasing need to develop alternatives to replace the damaged corneas with artificial substitutes. The aim of this study is to develop an engineered biomimetic corneal stroma that possesses the essential characteristics required for a corneal stroma substitute: high mechanical strength, optical transparency, promoting growth/migration of the native corneal cells and allowing the diffusion of essential gases and nutrients.
A novel approach has been used for developing a biomimetic corneal stroma (BCS) based upon the understanding of the corneal stroma’s highly arranged lattice structure using stacks of ultrathin, aligned collagen films. Suture retention strength and transparency of the BCS (stacks of 10, 20 and 30 films) at different wavelengths of visible light were examined as a measurement of the mechanical and optical properties of the BCS. Furthermore, corneal keratocytes were cultured between the BCS to evaluate their binding affinity and organization on the stacks. Human corneal epithelial cells were seeded on the BCS to evaluate the growth of the epithelial cells, and cells were seeded around the BCS to study the migration of these cells onto the BCS. Furthermore, the permeability of important nutrients and gases such as glucose and oxygen through the BCS was also measured.
The implantable BCS is made of ultra-thin (500-800 nm), transparent (98% of transmittance of visible light) and mechanically strong and peelable type I collagen films having highly aligned fibers and arranged to form orthogonal stacks. An increase in the suture retention strength was observed with a sight decrease in the transparency of the BCS as the number of stacked films increased from 10 to 30 collagen films. However, even after 6 weeks in an aqueous solution, the optical transparency in the visible wavelength of light remained over 90% for the BCS comprising of stacks of upto 30 films, indicating that the BCS maintains its transparency while possessing high suture retention strength, and also does not degrade in physiological solutions for long periods of time. A robust growth of corneal keratocytes and human corneal epithelial cells on the BCS was seen and epithelial cells migrated to the BCS to form a uniform monolayer of cells. Also, glucose and oxygen was diffused through the BCS, thus showing its competence for use as an implantable corneal stroma.
An implantable BCS having mechanically strong, transparent and cell growth support has been fabricated in this study. The engineered BCS may thus serve as an implantable corneal stroma equivalent for the millions suffering from corneal blindness worldwide.
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