Rather than grafting soft tissue or surgically implanting a molded polymer to fix deformities in the skin on a person’s face, doctors might in the future be able to inject a photoactivatable liquid polymer to reconstruct tissue. A research team led by Jennifer H. Elisseeff of Johns Hopkins University created a composite from methacrylated polyethylene glycol (PEG) and hyaluronic acid that, when cross-linked, forms an elastic material that mimics soft tissue (Sci. Transl. Med., DOI: 10.1126/scitranslmed.3002331). Hyaluronic acid is a natural polysaccharide that is part of the skin’s scaffolding. The researchers showed they can inject the composite liquid under the skin of rats and humans and then initiate cross-linking of PEG’s acrylate groups with a two-minute dose of 520-nm light applied through the tissue. When used in three patients, the PEG-hyaluronic acid composites maintained their shape for the 12 weeks of the trial, but the implants induced a small inflammatory response in surrounding cells. Elisseeff says her team would like to tune the composition of the polymer mixture to reduce this response and then undertake a larger clinical trial.