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Posted: August 22, 2007
Multifunctional nanoparticles combine ultrasound imaging and targeted anticancer therapy
(Nanowerk News) A new targeted drug delivery method, which combines two nanoparticles into one larger one, uses ultrasound to image tumors and release the anticancer drug doxorubicin from “nanobubbles” into the same tumors. This work, conducted by Natalya Rapoport, Ph.D., D.Sc., Anne Kennedy, M.D., and colleagues at the University of Utah, appears in the Journal of the National Cancer Institute ("Multifunctional nanoparticles for combining ultrasonic tumor imaging and targeted chemotherapy").
Cancer drugs can be targeted to tumors by delivering them in packets of nanoparticles, then releasing them with ultrasound. But this approach can be difficult because it requires a way to image the tumor prior to treatment. The researchers solved this problem by utilizing recently developed high-intensity-focused ultrasound instruments designed to both image and treat tumors.
Polymer-based nanobubbles filled with the chemotherapy drug doxorubicin were injected into mice. The bubbles accumulated in the tumors, where they combined to form larger “microbubbles.” When exposed to ultrasound, the bubbles generated echoes, which made it possible to image the tumor. Once imaging was complete, the researchers were able to focus the ultrasonic energy onto the tumor and simultaneously lower the amount of power needed to pop the bubbles and release the drug. The sound energy from the ultrasound popped the bubbles, releasing the drug.
In mice treated with this nanoparticle, the nanobubbles were more effective at blocking tumor growth than doxorubicin alone. Tumor targeting was passive, occurring because of the propensity of small nanoparticles to accumulate in tumors through the well-known enhanced permeability and retention effect.