Tiny Capsules for Drug Delivery

Shown here is a typical cross-section of a microscopic capsule - called a  "vault" - which occurs naturally in humans, monkeys, rats, and even slime molds.  With a hollow interior that is only a few millionths of an inch (40 nanometers) wide, vaults can be engineered to deliver drugs or DNA directly to cells.

Although tens of thousands of vaults are found in individual cells all throughout the body, biologists have yet to figure out what they are used for.  Mice have been genetically bred to no longer make these particles, but the animals and their cells are apparently unaffected.

The mystery about the vaults' biological purpose has not kept researchers from looking for practical uses.  Leonard Rome from UCLA and his colleagues have shown that vaults can function as nanoscale Trojan horses - smuggling foreign molecules past a cell's defenses.

Rome's team figured out how certain proteins come together to make the vaults (in the image above, high protein density is in red, while lower density is in green).  The researchers have attached foreign substances to one protein that makes up the interior wall.  When the vaults form, the desired cargo winds up in the small cavity. 

In laboratory tests, cells took up the vaults with the foreign molecules.  Possible uses of engineered vaults include:

• Delivery of cancer drugs directly to a tumor cell
• introducing DNA to correct genetic mutations
• timed release of drugs, enzymes and DNA
• detoxification or environmental cleanup, by sequestering toxic metals or poisons
• nanoscale switches in tiny electrical circuits

The team's work, which was funded by the National Science Foundation, was published in the March 7 issue of the Proceedings of the National Academy of Sciences.

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-- LiveScience Staff

Credit: Journal of Molecular Biology; Elsevier