Using tiny silica particles call mesoporous nanospheres to carry drugs inside living cells, Ames Laboratory chemist Victor Lin is studying different methods to control whether or not the particle delivers its pharmaceutical payload.

"First, the nanospheres are only about 200 nanometers in diameter, roughly the size of a virus, so they won't trigger an immune response in the body," Lin said. "They're also biocompatible so they can be readily absorbed by the cells."

But it's the structure of the nanospheres that makes drug delivery possible. The spheres have thousands of parallel channels running completely through them. Through capillary action, the spheres can soak up molecules of the drug to be delivered. When the channels are filled, the ends of channels are "capped" to safely seal the drug inside. Once the caps are in place, the nanospheres are "washed" to remove the drug from the outer surface.

The type of material used for the end caps, how they're held in place, and how they're released is the focus of Lin's work. The caps can be dendrimers, biodegradable polymers, genes, proteins, metallic nanoparticles, or semiconductor nanocrystals also known as quantum dots and are held in place by chemical bonds. Once the nanospheres are inside the target cells, a trigger is used to pop the caps off and release the drug.

"We're looking at two levels of control," Lin said of the trigger mechanism. "One level is to have the cell control the release and the other would be to control the release externally."

Lin explained that the chemical bond holding the cap in place can be engineered to be unphased by chemicals present in normal cells. However, in cancer cells t
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Contact: Kerry Gibson
kgibson@ameslab.gov
515-293-1405
DOE/Ames Laboratory
29-Mar-2006