A new biomaterial may help surgeons rebuild the delicate soft structures of the human face, like the cheeks, after a disease or injury has caused disfigurement. The material, which is half synthetic and half biological, can be injected under the skin as a liquid, massaged into shape, and then permanently “locked” by exposure to light.
Soft tissues are hard to replace, especially in the face. “We have metals and plastics for your bone,” says Jennifer Elisseeff, a TR35 winner in 2002 and one of the researchers on a paper published in Science Translational Medicine that describes the work. But surgeons lack good replacements for things like cheeks and lips—and even slight deformities can lead to severe social and emotional problems for patients. Existing implants are often insufficient for reconstructing larger defects, such as those left behind by tumor excisions or extreme trauma.
Alexander Hillel and his colleagues at Johns Hopkins University have created a new type of transplant material that addresses these problems. It’s a blend of hyaluronic acid—a biological material already used as a soft-tissue implant—and polyethylene glycol, a synthetic material. The blend is a liquid polymer that can be injected—thus avoiding the need for surgery. Once injected, the material can be sculpted into the necessary shape. When exposed to light of specific wavelengths, the messy tangle of polymer chains in the liquid implant rearrange into a stable, crosshatched form, stiffening the implant.
The fact that the LED uses visible light to set the implant is important, says Farshid Guilak, a professor of orthopedic surgery and biomedical engineering at Duke University: “Visible light is much safer than UV light, which can have a number of adverse effects, primarily DNA damage and cell death.”
Ali Khademhosseini, an associate professor at Harvard-MIT’s Division of Health Sciences and Technology, says the new material shows great promise. “To my knowledge, this is the furthest that such an approach has been taken, as the paper has extensive animal studies as well as pilot human studies,” he says.
To set the implants, the researchers devised a green-light LED array that can penetrate up to four millimeters of skin. It only takes two minutes of exposure before the implant fully sets, and there were no painful side effects.