Jul 092011
A bee swarm

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Research published in Nature Materials this month takes lessons from cooperation in nature, including that observed in insect swarms, to create better targeting methods for cancer therapeutics [1].

“Smart” anticancer drug systems can use mechanisms similar to swarm intelligence to locate sites of disease in the human body. Swarm intelligence arises when swarm behavior, for example bees flying and working together to locate sources of food, is used by the group “to solve a problem collectively, in a way that the individuals cannot” [2].

Insect swarms indeed often come up with solutions to a common task or problem that are “better than those produced through the most advanced mathematics” [2]. When researchers like Geoffrey von Maltzahn at MIT take lessons from swarm behavior and other examples of cooperation in nature (Figure 1), the results are engineered systems that have the potential to revolutionize the diagnosis and treatment of various cancers. Group or “swarm” problem-solving can handle the task of locating small collections of cancer cells inside a human body containing more than 100 trillion non-cancerous cells!

Geoffrey von Maltzahn and coworkers have designed a two-part system consisting of specialized nanoparticles that communicate with each other to amplify the delivery of drugs to sites of disease (Figure 2). Nanoparticles are very small objects, less that 1/1,000 the width of an average human hair, that can interact with individual human cells, proteins and even single molecules. Nanoparticles can also be modified in their shape, size and surface properties to remain in the bloodstream long enough to accumulate mostly in tumor tissues, which have leakier blood vessels than normal tissues.

Nanoparticles are thus excellent candidates for the transport of drugs to sites of disease. However, individual nanoparticles, even when equipped with “homing” molecules that lead them preferentially to cancer cells and tumorous tissues, still leave much to be desired in their targeting efficiency. Targeting efficiency is a measure of how well nanoparticles accumulate in cancer tissues.

Typically, drug-loaded nanoparticles must be delivered in the trillions to a subject animal [1] in order to reach even minimum therapeutic levels in a small, deep-seated tumor. This is a huge waste of nanoparticle agents and drug compounds, which not only are expensive and often hard to make, but also may do harm to healthy parts of the body when injected in such high numbers.

While many methods have been devised to improve the targeting efficiency of nanoparticles for disease diagnosis and therapy, Geoffrey von Maltzahn and coworkers may have come up with the most ingenious solution yet. They have created “scouting” or Signaling nanoparticles that pave the way to the location of a tumor inside a living mouse, and then communicate the tumor location to Receiving nanoparticles, or the rest of the “swarm.” This mechanism is similar to bee logic, where a bee swarm is able to “fly directly to a target that has been identified by (bee) scouts” [2].

Once the Signaling nanoparticles have recognized the presence of a tumor, they send signals to the drug-loaded Receiving nanoparticles broadcasting the tumor site [3]. In this way, just one scout is able to recruit more than 150 drug-loaded Receiver nanoparticles, equivalent to more than 35,000 individual drug molecules. This is an incredible amplification, similar to how a single “leader” or scout bee can recruit a whole beehive’s worth of his companions to a feeding site.

Read more . . .

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