Methods and compositions for imaging cancer cells

Disclosed are compositions comprising nanoparticles and uses thereof. Such nanoparticles include gold nanoparticles conjugated to glucose or a glucose derivative, which are useful as contrast agents in imaging methods such as computed tomography (CT). Nanoparticles disclosed herein are useful in imaging various cells, tissues, and organs, and are particularly useful in imaging tumors and tumor cells in vitro and in vivo.