Artificial Cells

Researchers are learning to make designer cells for dehydrated blood supplies and space-age medicines.

Red blood cells are great at carrying oxygen. Unfortunately, that's about all they do. Let's face it: with a little bit of help, they could be a lot more useful.

Imagine, for example, blood cells that could carry all kinds of things--medication as well as oxygen. Imagine blood that could be dehydrated, and stored for months or even years at a time. It could be carried by medics onto a battlefield--or by astronauts into outer space. Imagine blood that could be used for transfusions with no risk of AIDS or any other disease.

A group of university researchers is helping NASA develop an artificial cell that can do all this and more.

Bioengineers Dan Hammer and Dennis Discher of the University of Pennsylvania and Frank Bates of the University of Minnesota have created a special kind of molecule--a polymer--that forms something very like a cell membrane, and they've been able to coax these membranes into artificial cells, or polymersomes, that are stronger and more easily manageable than the real thing.

A polymer is simply a chain of smaller molecules that have been linked together. The cellulose in plants and the wool on sheep are natural polymers. Man-made polymers can be found in everything from nylon stockings to car parts to furniture stuffing.

Credit: Iowa St. University Red blood cells.

The polymers used in polymersomes are larger and heavier than the natural molecules in cell membranes: They've got a molecular weight of over 3600, compared to about 750 for phospholipids, the fatty acid molecules used by cells.

Manmade molecules can be crafted with an important characteristic, which many naturally occurring molecules share; they can be engineered to be amphiphilic, where one end seeks water, and the other end avoids it. In a water-based solution, such molecules spontaneously arrange themselves into a double-layer with their hydrophobic (water fearing) tails in the middle and their hydrophilic (water loving) heads on the outside.