New Scientist reports:

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 micrometres across to do it. But in some diseases, such as malaria and sickle cell disease, red blood cells lose this ability to deform.

Because of the small size of red blood cells and the demanding work they do, nobody has succeeded in making artificial versions to help people with such conditions.

Now though Joseph DeSimone, a chemical engineer at the University of North Carolina at Chapel Hill, US, thinks he knows how.

He 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, but binds easily with other substances, which makes it ideal for carrying cargo through the blood, says DeSimone.

Artificial blood replacement is likely to be a key biomedical enhancement technology in the near future. Ray Kurzweil frequently talks about the "respirocytes" which will act as supplemental mechanical red blood cells, 1000 times more efficient than their biological counterparts. Those who choose to replace even a small portion of their red blood cells with respiorocytes will be capable of what today could only be viewed as superhuman feats: running at sprinting speed for a quarter of an hour or more without breathing; sitting at the bottom of a swimming pool for hours at a time.

Of course, most of us don't want or need to be able to do such outrageous things. Respirocytes will initially be implemented to address many of the same kinds of conditions that DeSimone's polymer blood-cell substitutes are proposed for.They will also probably be used to give a much-needed boost to those recovering from serious illnesses or who have suffered some kind of major trauma. And speaking of illnesses and trauma, I can imagine respirocytes also serving as a delivery mechanism -- one of many that nanotechnology will provide -- for much more effective, and much less traumatic treatments for diseases such as cancer than anything currently available.