One of the biggest problems with transplanting biomaterials is getting the mostly aqueous material to stick in a very slippery space, says Jennifer Elisseeff, a biomedical engineer at Johns Hopkins University, who developed ChonDux and cofounded Cartilix. The adhesive in this case consists of chondroitin sulfate--a natural component of cartilage that is chemically modified to bind to the healthy cartilage surrounding the defect, as well as to the hydrogel. "It acts like a primer that helps paint stick to the wall," Elisseeff said at a panel at the recent EmTech conference in Cambridge, MA. The adhesive prevents scar formation between the new and old cartilage.

Elisseeff, who was a member of Technology Review's TR35 in 2002, and her team have tested the material in rabbits and goats and have found that more cells from the bone marrow get trapped in the blood clot when the hydrogel is present, compared with microfracture conducted without the gel. The researchers also noted that the defects fill faster with the biomaterial than without, and that the newly formed tissue more closely resembles true cartilage.

Results from a small clinical trial in Europe also look promising. According to findings presented at EmTech, magnetic resonance scans of the knee six months after the procedure showed that patients who received the hydrogel had grown more tissue than those undergoing traditional microfracture, and they reported less pain. Cartilix hopes to submit the data from its European study to the U.S. Food and Drug Administration (FDA) and begin a larger human trial in the United States.

While there are a number of studies on different carriers, such as hydrogels and other biomaterials, that can hold the cells in place and grow cartilage, "what's exciting about this work is that this bioadhesive can hold the hydrogel in place fairly strongly, giving it time to regrow cartilage," says Farshid Guilak, a biomedical engineer at Duke University School of Medicine. And because the biomaterial doesn't need to be seeded with cells prior to injection--a strategy that many research groups are investigating--it might be easier for Cartilix to obtain FDA approval for the material.

Elisseeff is adapting her biomaterials for other applications as well. For instance, she recently licensed some of her technology to Kythera Biopharmaceuticals, a company based in Calabasas, CA, that specializes in cosmetic medicine. The company is using Elisseeff's materials to develop light-activated cosmetic fillers that last much longer than those currently on the market. These fillers, which are typically injected into the skin along the sides of the mouth to minimize wrinkles caused by aging, tend to have a short life span. Patients often have the procedure repeated several times a year.

"With our materials, we shine light over [the area of the skin] that was injected and cross-link the materials so that they don't degrade as quickly," says Elisseeff. She says that Kythera plans to test the cosmetic fillers in patients in a couple of months. The first pilot study will take place in Beverly Hills.