Plastic red blood cells

Red blood cells travel through the blood­stream delivering vital oxygen to body tissues and taking away unwanted car­bon dioxide - and they have to squeeze through blood vessels as thin as 3 rni­crometres across to do it. But in some diseases, such as malaria and sickle cell disease, red blood cells lose this ability to deform.

Now, Joseph DeSimone, a chemi­cal engineer at the University of North Carolina at Chapel Hill, US, has created tiny sacks of the polymer polyethylene glycol just 8 micrometres across - in the range of human red blood cells - that are capable of deforming in a way that allows them to pass through the tiniest capillaries. Polyethylene glycol is biologically benign.