Luminescent quantum dots, making invisibles visible in bioimaging

Semiconductor quantum dots (QDs), their size-dependent tunable absorption and emission in the visible and near-infrared regions, narrow emission and broad absorption bands, large one- and multiphoton absorption cross sections, brightness, and photostability make them powerful light sources in the nanoscale region that will help to advance biotechnologies. This chapter overviews the present status and prospects of QDs by focusing on bioconjugation of QDs, and applications of bioconjugated QDs to surface-cell as well as inside-cell labeling for imaging and photodynamic therapy (PDT). In particular, it highlights the synthesis of biocompatible QDs, surface modification of QDs, conjugation of QDs with a variety of ligands and antibodies, potential targets of bioconjugated QDs in cells, nonspecific and specific surface-cell labeling, nonspecific and specific delivery of QDs in cells, and PDT based on QDs. Such information will be helpful for both applications of QDs for bioimaging and extension of QD technologies to other nanoparticles.