The long quest for artificial blood

One of the most valuable substances in the world has never been replicated. Are we close?

Blood is in high demand almost everywhere, but its seemingly endless complexity has confounded scientists for decades. Illustration by Ibrahim Rayintakath.

In a pair of fluorescent-lit rooms on both sides of the Atlantic, the guinea pigs awaited their fate. They were not literally guinea pigs. Two were lightly sedated, extremely fluffy white rabbits resting on pee pads; the other was Nick Green, a sixty-four-year-old part-time administrator at the University of Cambridge who reclined, hands clasped atop his patterned sweater, on the starched sheets of a hospital bed. All three were hooked up to machines that provided a readout of their vital signs, and all three were prepared to have a syringe of manufactured blood injected into their veins.