Semiconductor nanocrystals have unique optical properties due to quantum confinement effects, and a variety of promising approaches have been devised to interface the nanomaterials with biomolecules for bioimaging and therapeutic applications. We present a novel scheme of synthesizing fluorescent nanocrystal quantum dots (NQDs) using DNA aptamers for growth inhibition of human cancer cells. An anti-cancer aptamer DNA sequence is used as a capping ligand to directly synthesize highly fluorescent NQDs in aqueous solution. The DNA aptamer retains its unique secondary structure on the NQD surface, which is necessary for selective and specific binding to its target protein, nucleolin. The aptamer-functionalized NQDs are proposed as proliferation inhibitors, and their efficacy is examined with MCF-7 human breast cancer cells using hemacytometry and MTT assay. The NQDs show 3-4 times greater inhibition efficacy than DNA drugs alone. In vitro cytotoxicity of these NQDs is investigated with mouse fibroblast cells, and the NQDs are found to be non-toxic under the experimental conditions. The nanoparticle-based therapeutic schemes devised in this work should be valuable in developing a multifunctional drug delivery and imaging agent for biological systems.

J.H. Choi, K.H. Chen, and M.S. Strano; J. Am. Chem. Soc. 128, 15584 (2006)