Quantum Dot Biofunctionalization

We have shown the efficacy of Quantum Dots (qdots), nano-scale fluorescent particles made of semi-conductive material, as versatile biologically functional research tools. This functionality depends upon a series of chemical transformations that produce stable, aqueous, biomolecule-bound qdots with high quantum yield. We utilize the metal binding and chelating properties of the amino acid histidine to displace hydrophobic surface ligands and to phase-transfer qdots from organic to aqueous media. The intermediate binding strength of histidine to qdot surface facilitates its exchange with a variety of strongly binding thiolated biomolecules. Ligand profiles are subsequently characterized via FTIR, NMR, and gel electrophoresis. Negatively-charged aqueous qdots are shown to be taken-up and contained within phospholipid liposomes formed via several different protocols. Flexible liposome synthetic procedures allow intercalation of a number of moieties into liposomal membranes, including hydrophobic dyes and hydrophobic qdots. Possible implications for cellular delivery are discusse