YOU can't get blood from a stone, but it seems you can make imitation red blood cells from polymers.
Just like real red blood cells, these pretenders can squeeze through spaces much smaller than their own diameter, and absorb and release molecules to order, including oxygen. They could be used to disperse drugs evenly throughout the body or given to people who need a transfusion.
Real red blood cells owe their agility to their "biconcave" shape (see picture). So Samir Mitragotri of the University of California and his team added 7-micrometre-wide balls made of a polymer called PLGA to a solvent that causes the balls to collapse. They coated the resulting, tyre-shaped particles in a layer of protein, and dissolved away the polymer core, leaving behind soft biodegradable shells the size and shape of real red blood cells. ...