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Sunday, June 5, 2011

Targeting tumors with nanoparticles

The idea of using nanoparticles to target tumors is not new. What is new is the idea of using differences in acidity to direct nanoparticles specifically to tumors. This idea was conceived and successfully tested in mice by Paula Hammond and her colleagues from MIT.
Because tumors grow much more rapidly than neighboring tissues, they use much more oxygen and consequently are more acidic than normal cells. Hammond’s team took advantage of this difference in designing their multilayered nanoparticle capsules. The outer layer of each nanoparticle protects it from degradation in the bloodstream, but falls apart in the acidic vicinity of cancer cells. The next layer is positively charged, allowing the capsule to be absorbed through the tumor cell wall. Inside the final layer could be an anti-cancer drug, or a cell labeling system such as a quantum dot.

The polymer coating (light blue) is shed as the particle approaches a tumor, exposing positive charges. Those charges help the particle be absorbed through the tumor cell membrane.
Image: Stephen Morton.
The good news is that this system should be effective against any type of cancer. Rather than targeting markers specific to a few types of tumors, the traditional approach of nanotechnology, these new nanoparticles accumulate in regions of rapid growth, the hallmark of just about any cancer we might wish to eradicate.

The bad news is that even Hammond does not expect to see human trials for five to ten years. Such is the pace of medical science.