One-step conjugation of biomolecules to luminescent nanocrystals

The development of optical probes is crucial to the elucidation of complex biological and chemical problems. Existing fluorescent labels tend to photobleach, have low luminescence, and are sensitive to the environment. These problems can be overcome by the use of semiconductor quantum dots. These ZnS-capped CdSe quantum dots are synthesized in an organic media. To use them for biological labeling, the quantum dots are made water-soluble by adsorbing bifunctional molecules onto the surface. This step is crucial for the successful conjugation of biomolecules onto the surface. In this report, a new method for the direct adsorption of biomolecules onto the surface of quantum dots is demonstrated. Biomolecules such as glutathione, mercaptosuccic acid, and histidine are directly conjugated to luminescent quantum dots by S-Zn or N-Zn bonding.