Artificial Cells

Polymersomes can also be engineered so that some types of cells do react to them. Hammer, Discher and colleagues can add to their polymersomes particular molecules that latch onto the cells they're targeting. Typically, says Hammer, the polymersomes float through the bloodstream for about 18 hours before they reach their destination and grab onto the target cells.

Credit: University of Pennsylvania This sequence of microscopic photos shows how a tough crosslinked polymersome can be dehydrated (for, e.g., easy storage and transportation) and rehydrated again.

The key word is "target." Doctors using polymersomes wouldn't have to pepper the entire body with medications. They could be targeted--sent only to the places they're needed. Arthritis medications, for example, could be sent only to a patient's swollen fingers, without the risk of causing reactions elsewhere. Polymersomes could carry cancer-zapping pharmaceuticals directly to a tumour. They could incorporate imaging agents like iron oxide particles, which can be detected by magnetic resonance imaging. If these particles are encapsulated into polymersomes designed to latch onto cancer cells, they'd be able to locate small tumour. cells that have migrated through the body.

Polymersomes could theoretically be designed to carry both the imaging agents that locate a problem, and the medication that treats it.

Using manmade materials to produce an artificial cell is "a highly novel concept," says Hammer. "I think that NASA saw this as a wonderful material, and they wanted to see how far it could evolve." In some conditions, he says, polymersomes take on shapes that are very reminiscent of the ones biological cells take on when, for instance, they're dividing.

And Hammer and his colleagues are still exploring the possibilities. They're experimenting with different types of polymers, to see how the capabilities of artificial cells can be expanded.

The most exciting applications of polymersomes, believes Hammer, are still to come.