Quantum dots detect metastatic lesions

By injecting quantum dots into tumors, investigators at Carnegie Mellon University have been able to image sentinel lymph nodes in animals using near-infrared light. These results could lead to a simple, non-invasive method for detecting metastasis.

Reporting its work in the journal Bioconjugate Chemistry, a research team headed by Byron Ballou, Ph.D., used polymer-coated, water-soluble quantum dots to map the lymph nodes that drain tumors in mouse models of human cancer. In many types of cancer, metastatic lesions first appear in these lymph nodes, which are why they are known as sentinel lymph nodes. In these experiments, the investigators injected the quantum dots directly into the tumors and then tracked the quantum dots through the skin using near-infrared fluorescence microscopy.

The investigators found that they readily observed the quantum dots moving out of tumors and into the lymph system. The researchers noted that drainage began almost immediately after injection, and that the quantum dots clearly mapped out the connected string of lymph nodes. Using several varieties of water-soluble quantum dots, the researchers found to their surprise that there was little difference in lymph node illumination.

The investigators noted, too, that they have been following a group of animals that they have injected with quantum dots for over two years now. The researchers have found no evidence of toxicity in these animals even though they can still observe quantum dots within the animals.

This work is detailed in a paper titled, “Sentinel lymph node imaging using quantum dots in mouse tumor models.” Investigators at Quantum Dot, now a part of Invitrogen, and Aviir also participated in this study. This paper was published online in advance of print publication. An abstract of this paper is available through PubMed. View abstract.