Applications of T-lymphoma labeled with fluorescent quantum dots to cell tracing markers in mouse body

Photoluminescent semiconductor quantum dots (QDs) are novel nanometer-size probes that have found bioimaging. Here we imaged a cell line of mouse lymphocytes. QDs were actively taken into the target cells by endocytotic pathways. The fluorescence of QDs held in the endosomes could be studied for more than a week and remained stable luminescence against cell activation induced by concanavalin A, phytohemagglutinin, phorbol myristate acetate, and calcium ionophore A23187. These results suggested that QD-labeling was stable and did not affect either cell activation or cell function. When QD-labeled cells were intravenously injected into mouse, they remained in the peripheral blood in a concentration of approximately 10% up to 5 days after injection using both fluorescence microscopy and flow cytometry. In addition, approximately 20% of QDs were detected in the kidneys, liver, lung, and spleen and could still be observed 7 days after injection. These results suggested that fluorescent probes of QDs might be useful as bioimaging tools for tracing target cells over the period of a week in vivo.