ARCHIVED - Biosynthetic Corneas Could Help Restore Sight to Millions
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June 03, 2003— Ottawa, Ontario
|Dr. Dave Carlsson with molds used to create artificial corneas for testing|
With more than three decades as a physical chemist at the NRC Institute for Chemical Process and Environmental Technology (NRC-ICPET), Dr. David Carlsson has helped develop many improvements in plastics and fibres. But his latest assignment may prove the crowning achievement of his career: building a tissue engineered (TE) cornea that could help restore sight to millions of visually impaired people.
The cornea is the clear cover on an eyeball, like the crystal on a watch, which focuses light onto the eye's retina. Although built to last a lifetime and guarded by a vast number of nerves, corneas can turn opaque from injury or disease, causing blindness. Fortunately, damaged corneas can be replaced by transplantation. But the procedure suffers from the same limitation as other organ transplants: a serious shortage of donors.
|Cornea material is surgically implanted to test for nerve and blood vessel ingrowth|
"North America is barely self-sufficient in donated corneas, and Asia and the Third World have a huge shortage," says Dr. Carlsson, Researcher Emeritus at NRC-ICPET. "The World Health Organization estimates that about 10 million people could use a cornea replacement right now."
Since 2000, he and his NRC colleagues have been working with Dr. May Griffith, an internationally recognized cell biologist, and Dr. Frank Li, a skilled polymer chemist, both at the University of Ottawa Eye Institute, to develop a synthetic structure with essentially the same properties as a natural cornea. "A human cornea is as tough as shoe leather," says Dr. Carlsson. "It's incredibly strong and has an exquisite architecture; there are about 300 layers stacked on top of each other."
|Dr. Frank Li, University of Ottawa, prepares Biosynthetic material|
According to Dr. Carlsson, a human cornea is 80 per cent water and 20 per cent natural polymers. "The dominant polymer is collagen, nature's Swiss army knife — it's found everywhere. The rest are sugar-like molecules. So there's a micro-fibrous material — collagen — and resins to bind it all together. It would be nice to copy how nature makes corneas, but it would take 100 years to get it right."
Instead, the NRC-ICPET approach has been to work closely with their University of Ottawa partners to identify the ideal properties of a synthetic cornea. "These are our main priorities: keep the synthetic cornea transparent, make it cell-friendly, and increase the toughness," — says Dr. Carlsson.
|Artificial corneal material|
|Dr. May Griffith, University of Ottawa, with engineered tissue for artificial corneas
So far, the first two criteria have been met. The team has produced a synthetic material that's almost invisible in water, and is compatible with the cells found in a human eye. "A synthetic cornea needs to coexist with epithelial cells, which serve as the first line of defense," says Dr. Carlsson. "We want epithelial cells to grow perfectly over the cornea. We want the nerves to reattach so they'll tell the brain when to blink and generate tears so that the cornea won't dry out. We're trying to get the body's own cell systems to turn on and repair the damage by providing the right environment in our synthetic corneas, rather than just implant a chunk of clear plastic."
The team's main hurdle now is to increase the strength of their synthetic materials. "A skilled surgeon could implant the TE cornea into an eye. But it's still a long way from the strength of the human cornea," says Dr. Carlsson.
"The ball is in Dave's court now," says his collaborator, Dr. Griffith. Will he succeed? "Probably. He doesn't have a choice!" she jokes.
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