IRDye® 800CW 2-DG is a fluorescent optical imaging agent that has been shown to be reactive with implanted tumors derived from a number of cell lines including A431, SW620, 3T3-L1, and PC3LMN4. An example is shown in Figure 1. The optical agent exhibits the expected dose response with increasing concentrations of the agent in both cell based and animal experiments. Uptake of the agent can be effectively blocked with either unlabeled 2-DG or glucose, confirming its specificity. Confocal microscopy demonstrated conclusively that IRDye® 800CW 2-DG is taken up by the cell and localized in the cytoplasm. While the exact mechanism of IRDye® 800CW 2-DG uptake is not known, there is strong evidence for the involvement of the GLUT transporter system.