Researchers have demonstrated the first graphene-based imaging agent to target a tumor in live mice (ACS Nano, DOI: 10.1021/nn204625e). Weibo Cai, of the University of Wisconsin School of Medicine & Public Health, and colleagues wondered whether a flake of graphene could form a low-toxicity scaffold to carry imaging labels or even cancer drugs to tumors. First, they coated tiny sheets of graphene oxide with strands of the polymer polyethylene glycol. On some of the polymer chains, they attached an antibody that binds to a protein found on the blood vessels growing around some tumors. On other polymer chains, the researchers added a copper-based radiolabel. The scientists injected the graphene oxide probes into mice with breast cancer tumors. The team used positron emission tomography imaging to monitor where, and at what concentrations, the probes accumulated. Within 30 minutes, the graphene oxide probe appeared in tumor blood vessels and remained there at a constant level until the study ended, 48 hours later. The team concluded that the probe gets to tumors quickly and persists there for some time, two important features for a potential nanomedicine.