One of the problems with artificial skin is its vulnerability to infection. Synthetic skin is used in burn treatment and plastic surgery, but blood vessels, which carry the immune system’s machinery, may not connect to the new dermis for a week or two. “Without blood vessels, bacteria can grow and cause infection,” says Ioannis Yannas, a bioengineer and materials scientist at MIT who helped develop the first artificial-skin product, approved by the U.S. Food and Drug Administration in the mid-1990s. In a new approach, cultured skin cells are genetically modified to produce higher levels of an antibacterial protein. The cells multiply in the lab and are injected into a collagen matrix of artificial skin. “We’re using genetic modification to try to get the cultured skin to behave more like normal skin,” says Dorothy Supp, a researcher at the Cincinnati Shriners Hospital for Children in Ohio, who led the project. Supp cautions that the engineered cells are far from clinical use: the true test of their bacteria-fighting properties will come in the complex environment of a real wound. The researchers are planning experiments in animal models. The technique could eventually be used to make skin that can sweat and tan after implantation.