Here’s an exciting project by the interdisciplinary team of ophthalmologists and chemical engineers from Stanford. The promise of an artificial cornea comes from the unusual properties of a new material called Duoptix™. The cornea is constructed of a dual-network hydrogel with a clear center and peripheral pores. It is hoped, that once implanted, the epithelial cells from the eye will infiltrate the pores and secrete collagen, thus integrating the artificial cornea into the indigenous tissue.
From the Stanford press office:
Called Duoptix™, the material can swell to a water content of 80 percent–about the same as biological tissues. It’s made of two interwoven networks of hydrogels. One network, made of polyethylene glycol molecules, resists the accumulation of surface proteins and inflammation. The other network is made of molecules of polyacrylic acid, a relative of the superabsorbent material in diapers…
Myung’s project [David Myung is an MD/PhD student at Stanford –ed.], funded by Stanford’s Bio-X interdisciplinary biosciences program, was to design, fabricate and characterize a bioengineered cornea based on the dual-network hydrogel. The result was a disc with a clear center and tiny pores populating the periphery. Myung calls the pores engineered into his artificial cornea the “homes” he built for cells that need to infiltrate the artificial lens and integrate it with surrounding natural tissue.
“If you build it, they will come,” Myung says. “The cells move in, and they bring furniture too–meaning the collagen they secrete. They even ‘remodel.'” Collagen binds to the edge of the synthetic disc and forms a junction between natural and synthetic tissues. Then a clear layer of epithelial cells grows over the disc.
Stanford’s program to develop an artificial cornea is “broadly interdisciplinary,” Frank says. [Curtis Frank is a chemical engineering professor –ed.] Christopher Ta, an assistant professor of ophthalmology and ophthalmology residency director at the Stanford University Medical Center, leads the effort with Frank. Ta says scientists have tried to develop artificial corneas for half a century, but prototypes were not well tolerated. Infections developed around implants. Eyes extruded implants…
The researchers are now testing the material for biocompatibility in animal models. Animals have tolerated artificial corneas with no problems in trials as long as eight weeks, Ta says. The material remains perfectly clear, he says. Longer trials are a next step.
Other ocular applications of the hydrogel could include more comfortable extended-wear contact lenses.
Inlays and onlays are also possible. The cornea contains layers–a top layer of protective epithelial cells, a middle layer called stroma that provides the collagen matrix that gives the cornea its shape and an innermost endothelial layer. With onlays, some of the epithelial layer can be scraped away and replaced with a hydrogel contact lens. The lens becomes biointegrated when clear epithelial cells grow over the top of the lens. Inlays, on the other hand, are implanted within the stroma.