Semiconductor Nanocrystals for Biomedical Imaging

The principal objective in Phase I is to demonstrate methodologies for the stabilization and functionalization of luminescent nanoparticles (quantum dots, QDs) to be used in cellular imaging. This will be achieved by encapsulating QDs in two different types of water-soluble polymer delivery vehicles. Both types of polymer will eventually be functionalized with specific targeting ligands in order to facilitate imaging of selected cellular targets. The physicochemical properties that make QDs well suited for such imaging applications include: their quantum yields, small size, narrow emission wavelengths which effect little or no spectral overlap among multiple-size QD tags, their photostability, and their very high absorption efficiencies which obviate the need for high power requirements for excitation. In Phase I, we will synthesize the polymers and use them to encapsulate QDs of defined diameter. Each nanoparticle complex will be characterized in terms of luminescence profile, quantum yield, photostability, and extinction coefficient. These properties will be examined in a variety of environments to determine any pH- or solvent dependent aspects of fluorescence behavior. Both types of encapsulated nanoparticle probes will be used to transfect cultured mammalian cells in order to assess QD luminescence in a physiological milieu.