The key to this research was the discovery that combining two different nanoparticles – one to find and adhere to the cancerous cells and the other to kill the cells – actually worked. Typically nanoparticles in the bloodstream have a hard time staying active, either because they break down, or because the body’s own defense mechanisms, immune cells called mononuclear phagocytes, remove them. By working two nanoparticles in tandem, the researchers were able to improve the amount of time the ‘cocktail’ stays active in the bloodstream, meaning the longer time the particles have to reach the target cancer.

“This study represents the first example of the benefits of employing a cooperative nanosystem to fight cancer,” said Michael Sailor, a professor of chemistry and biochemistry at the University of California, San Diego and the primary author of a paper describing the results, which is being published in a forthcoming issue of the Proceedings of the National Academy of Sciences.

The researchers designed one type of responder particle with strings of iron oxide, which they called “nanoworms,” that show up brightly in a medical magnetic resonance imaging, or MRI, system. The second type is a hollow nanoparticle loaded with the anti-cancer drug doxorubicin. With the drug-loaded responder, the scientists demonstrated in their experiments that a tumor growing in a mouse can be arrested and then shrunk. “The nanoworms would be useful to help the medical team identify the size and shape of a tumor in a patient before surgery, while the hollow nanoparticles might be used to kill the tumor without the need for surgery,” said Sailor.

[Source: University of California San Diego]

This research is the first time a combination of nanoparticles has been used (successfully) in test animals. Like much of nanomedicine, the application of this approach in human cases is a way off (possibly years).