September 19th, 2006
Biomimetic artificial corneas
There are at least 10 million people worldwide who are blind due to damaged or diseased corneas. Right now, the only way to help people affected with corneal blindness requires a corneal transplant. This implies to take a cornea from a dead person and this is not always successful: there is a rejection rate of about 20 percent. Now, an interdisciplinary team from Stanford University has developed an artificial cornea made from a hydrogel. As the researchers have filed four patents for ocular applications of this hydrogel, there should be artificial corneas on the market in a near term future. But read more…
The team who developed this biomimetic material was composed of chemical engineer Curtis Frank, David Myung, a medical student also working on a doctorate in chemical engineering in Frank’s lab, and Christopher Ta, an assistant professor of ophthalmology. Here is a short description of this new material.
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.
"Think of a fishnet, but think of a 3-D fishnet," says Frank [...] "It’s a strong, stretchy material." That makes it able to survive suturing during surgery. The biocompatible hydrogel is transparent and permeable to nutrients, including glucose, the cornea’s favorite food.
Below is a picture of this artificial cornea "made of a dual-network hydrogel with a clear center and peripheral pores. Cells infiltrate the pores and secrete collagen, which integrates the artificial cornea into the surrounding natural tissue." The pattern used to make this artificial cornea was created with photolithography. (Credit: Stanford University)
Here is a picture of David Myung holding a sample of the hydrogel, with ophthalmology assistant professor Christopher Ta (left) and chemical engineering professor Curtis Frank (right). (Credit: Stanford University)
Other researchers have also tried to develop artificial corneas before. But the Stanford team thinks their approach is the best one so far.
"Only two or three are on the market, but they are only used in last-ditch efforts [when transplants are rejected]," [Myung] notes. Stanford’s artificial cornea is "the most biomimetic," he says, with a water concentration and mechanical properties that rival those of the natural cornea.
Besides helping blind people, this hydrogel might also be used to build more comfortable extended-wear contact lenses or "implantable contact lenses that can be replaced if the prescription changes."
Source: Stanford University news release, September 11, 2006
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