An antibody-conjugated internalizing quantum dot suitable for long-term live imaging of cells.

Quantum dots (QD) are fluorescent semiconductor nanocrystals that are emerging as superior alternatives to the conventional organic dyes used in biological applications. Although QDs offer several advantages over conventional fluorescent dyes, including greater photostability and a wider range of excitation and (or) emission wavelengths, their toxicity has been an issue in its wider use as an analytic, diagnostic and therapeutic tool. We prepared a conjugate QD with an internalizing antibody and demonstrated that the QD-antibody conjugate is efficiently internalized into cells and is visible even after multiple divisions. We demonstrate that the internalized QD is nontoxic to cells and provides a sensitive tool for long-term molecular imaging.