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Any fan of Star Trek knows that simply shining light on an injury will heal many wounds in the future. Now scientists have brought that future a bit closer. In a new study, researchers have found a way to stimulate the growth of blood vessels—an important part of healing—by hitting the skin with ultraviolet light.

In the past decade, scientists have used light to manipulate the chemistry of cells in a dish—but they’ve struggled to do the same in living organisms. “There are hundreds of different types of cells; you have a lot more other biological molecules present,” says bioengineer Andrés García of the Georgia Institute of Technology in Atlanta.

So García and colleagues turned to a water-based gel, or hydrogel, impregnated with a molecule called RGD peptide. The body uses this peptide to signal cells to stick to and grow on new tissues. The team then attached another molecule to the RGD peptide to shut it down. When the researchers shone UV light on the hydrogel, this molecular disguise dropped off and the RGD peptide became active.

The scientists then moved to animal experiments. They made cuts on the backs of mice and implanted samples of the hydrogel underneath their skins. They exposed some samples of hydrogel to UV light immediately after implantation, and they exposed others either 7 or 14 days later.

Cells grew just as well around the peptide-impregnated samples, irrespective of when they were irradiated, the team reports online this week in Nature Materials. When the RGD peptide was activated immediately after implantation, the mouse's immune system recognized it as a foreign body and surrounded the hydrogel with scar tissue. When the peptide was left dormant for a few days before activation, however, the body's immune response was much weaker and the hydrogel became better integrated into the mouse's tissue.

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