Researchers at North Carolina
State University have successfully modified a common plant virus to deliver
drugs only to specific cells inside the human body, without affecting surrounding
tissue. These tiny "smart bombs" - each one thousands of times smaller
than the width of a human hair - could lead to more effective chemotherapy treatments
with greatly reduced, or even eliminated, side effects.
Drs. Stefan Franzen, professor of chemistry, and Steven Lommel, professor of
plant pathology and genetics, collaborated on the project, utilizing the special
properties of a fairly common and non-toxic plant virus as a means to convey
drugs to the target cells.
The researchers say that the virus is appealing in both its ability to survive
outside of a plant host and its built-in "cargo space" of 17 nanometers,
which can be used to carry chemotherapy drugs directly to tumor cells. The researchers
deploy the virus by attaching small proteins, called signal peptides, to its
exterior that cause the virus to "seek out" particular cells, such
as cancer cells. Those same signal peptides serve as "passwords" that
allow the virus to enter the cancer cell, where it releases its cargo.
"We had tried a number of different nanoparticles as cell-targeting vectors,"
Franzen says. "The plant virus is superior in terms of stability, ease
of manufacture, ability to target cells and ability to carry therapeutic cargo."
Calcium is the key to keeping the virus' cargo enclosed. When the virus is
in the bloodstream, calcium is also abundant. Inside individual cells, however,
calcium levels are much lower, which allows the virus to open, delivering the
cancer drugs only to the targeted cells.
"Another factor that makes the virus unique is the toughness of its shell,"
Lommel says. "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."
The researchers believe that their method will alleviate the side effects of
common chemotherapy treatments, while maximizing the effectiveness of the treatment.
Posted February 12th, 2009
