May 1, 2006
Targeted Quantum Dots Image Tumor Blood Supply
Using polymer-coated cadmium telluride/zinc sulfide (CdTe/ZnS) quantum dots targeted to a molecule found on newly growing blood vessels, a team at the Stanford University Center of Cancer Nanotechnology Excellence (CCNE) has shown for the first time that quantum dots can image a tumor’s blood supply. This development holds promise for the development of new ways of detecting cancer as well as identifying the edges of a tumor during surgery.
Reporting its work in the journal Nano Letters, a group of investigators led by Xiaoyuan Chen, Ph.D., Sam Gambhir, M.D., Ph.D., and Shan Wang, Ph.D., all project leaders in the Stanford CCNE, described its construction of a CdTe/ZnS quantum dot decorated with 30 to 50 copies of a small protein, or peptide, known as RGD. This peptide binds specifically to a much larger protein, called αvβ3, found on the surfaces of new blood vessels growing in response to tumor cell signals, as well as on some tumor cells. Tests with cultured human tumor cells confirmed that these quantum dots bound tightly only to those cells that have αvβ3 on their surfaces.
Based on these promising results with isolated cells, the investigators explored whether these targeted quantum dots would bind to human tumors growing in mice. In fact, tests with tumor-bearing animals showed that the quantum dots were visible in tumors within 20 minutes after injection. The fluorescent signal from the tumor-bound quantum dots peaked at six hours after injection, and optical images clearly outlined the tumors against a very low fluorescent background. Subsequent microscopic examination of the tumors showed that the quantum dots were congregated on the blood vessels growing in and around the tumors.
This work, which was supported in part by the National Cancer Institute’s Alliance for Nanotechnology in Cancer, is detailed in a paper titled, “Peptide-labeled near-infrared quantum dots for imaging tumor vasculature in living subjects.” An abstract of this paper is available through PubMed.