Friday, February 13, 2009

Researchers Create Cancer-Killing Smart Bomb From Plant Virus

A North Carolina State University team has created a new cancer-killing smartbomb candidate out of a plant virus, like the one shown here. Advantages of this approach include its biocompatibility and ample cargo space (the spherical void inside the outer shell). (Source: Stanford Synchrotron Radiation Laboratory)

"Someone set us up the bomb"

One of the hottest areas of research in nanotechnology is the creation of tiny "smart bombs" which are able to latch on to a specific cell and deliver a chemical payload. While such devices would be useful to treat a variety of disease, cancer is their primary target.

Researchers at North Carolina State University have used modified plant viruses to create the latest version of the smart bomb. By selectively targeting specific cells in the body for payload delivery, it could greatly reduce the effects of toxic treatments like chemotherapy on healthy cells, while increasing the efficacy of killing cancer cells.

For the project Dr. Stefan Franzen, professor of chemistry, and Dr. Steven Lommel, professor of plant pathology and genetics, modified a typical non-toxic plant virus. The gutted virus has a "cargo space" of 17 nanometers, in which it typically carries its DNA. This space can be filled with drugs to deliver to cells. The virus is coated in small proteins, called signal peptides, which help it find its targets.

By modifying these signal peptides to match those in cancer cells (but not in healthy cells) accepting deliveries, the virus can be injected into the cell and deliver its payload. Professor Franzen says his team’s smart bomb is better than past designs, stating, "We had tried a number of different nanoparticles as cell-targeting vectors. The plant virus is superior in terms of stability, ease of manufacture, ability to target cells and ability to carry therapeutic cargo."

The plant virus uses calcium concentrations to trigger the release of its cargo. When in the bloodstream or intercellular matrix the high calcium concentration prevents the cargo from being released. However, inside cells the calcium concentration drops, and the virus dumps its cargo.

Professor Lommel describes another perk of using the virus, stating, "Another factor that makes the virus unique is the toughness of its shell. When the virus is in a closed state, nothing will leak out of the interior, and when it does open, it opens slowly, which means that the virus has time to enter the cell nucleus before deploying its cargo, which increases the drug's efficacy."

As with other efforts, a critical key is to identify chemical markers on cancerous cells and compare them with those in healthy cells. Much work needs to be done before proper marker proteins can be added to these smart bombs to effectively target cancer. In other words -- efforts like this one have built a powerful weapon; it just needs its targeting system completed.