Henrik Clausen and his colleagues at the University of Copenhagen have managed to turn any type of blood into type O, the kind that all people can safely receive. The challenge has been how to remove the molecular badges — A, B, and AB — that lie on the surface of the red blood cells and can trigger rejection by a patient’s immune system. Twenty-five years ago, researchers identified an enzyme in coffee beans that could change type B to O, but the process was too inefficient for widespread use. What Clausen’s team has done is to identify two bacterial enzymes that can do the job — and do it a thousand times more effectively. Clinical trials evaluating the safety of enzyme-converted blood in humans are already under way, with initial results expected later this year.
But one day, if University of Sheffield chemist Lance Twyman has his way, type O, and perhaps all donor blood, might be unnecessary. Twyman has been developing synthetic plastic blood, and he says the idea isn’t as outlandish as it sounds. “We’ve used polymer chemistry to try to mimic what nature does,” Twyman says. “In the end, we get a synthetic molecule that has the same size, shape, and function as hemoglobin. It reversibly binds oxygen, is soluble in water, and is made from polymer units that are known to be safe in the body.”
The plastic product still needs to undergo biological testing, and the hemoglobin replacement polymer is not yet a total blood substitute, but it is a crucial first step. The substance can be stored as a dehydrated paste and then quickly reconstituted with water. “Soldiers could carry it with them, and then if they needed blood quickly, they could add water,” Twyman says. “A lot of people die from relatively minor injuries — they just bleed to death. This really has the potential to save lives.”