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Posted: March 5, 2007
Targeted nanoparticles image early tumors
(Nanowerk News) A well-established fact in cancer therapy is that early tumor detection improves the odds that a patient will survive the disease. Now, using nanoparticles targeted to the tiny blood vessels that surround even the smallest tumors, researchers at the Siteman Center for Cancer Nanotechnology Excellence (CCNE) have developed a radioactive imaging agent that was able to identify human tumors in rabbits. This work appears in the International Journal of Cancer ("Imaging of Vx-2 rabbit tumors with ανβ3-integrin-targeted 111In nanoparticles.").
Gregory Lanza, M.D., and Samuel Wickline, M.D., both at Washington University in St. Louis, led the group of investigators that created perfluorocarbon nanoparticles, each containing an average of 10 atoms of the radioactive element indium-111, an agent used in a variety of biomedical imaging applications. To target tumors, the researchers added a molecule that recognizes and binds to æνβ3-integrin, a complex molecule found on the surface of new blood vessels.
When injected into rabbits bearing human tumors, these nanoparticles quickly accumulated in and around the tumors. Using a standard gamma camera, the investigators were able to detect the nanoparticles at the site of tumors within 15 minutes after injection. The gamma signal persisted over the course of two hours. In contrast, the researchers detected no nanoparticle accumulation in the muscle, a tissue rich with blood vessels, demonstrating the tumor-targeting capability of these nanoparticles.
The researchers note that while the sensitivity of this method is high, its spatial resolution is low. In practice, then, this method would best be used in conjunction with imaging techniques such as fluorine-19 magnetic resonance imaging (19F-MRI). Gamma imaging would then provide sensitive detection of small tumors, while 19F-MRI would pinpoint the location of the tumors for subsequent surgical removal.