If the current wave of vampire stories is to be believed, humans can peacefully co-exist with vampires.

The Twilight book trilogy has 'vegetarian' vampires living on animal blood, and in the TV series True Blood, Japanese scientists have developed a synthetic blood substitute.

Back in the real world, the hunt for a blood substitute could not be truer. In fact, the quest to create artificial blood is big business, with more than one billion pounds being spent over the last 20 years in an attempt to create a true alternative to blood.

Among those around the globe seeking a viable blood alternative are scientists at the University of Essex who have just submitted a worldwide patent for their engineered hemoglobin.

Over 75 million units of donated blood are given to people worldwide for use in hospitals. However, there are growing concerns about its use in routine operations.

A true blood substitute would be very useful as it could have a long shelf life, be stored away from hospitals, need not be matched for blood group and be guaranteed free of contamination by any present or future viruses.

The starting materials for blood substitutes have included chemicals used to help make atom bombs, cow blood and blood grown in bacteria. However, to date the world's scientists have failed to produce a safe alternative to blood. The real world is more Daybreakers than True Blood.

The reason for this failure, according to Professor Chris Cooper, a biochemist and blood substitute expert at the University of Essex, lies in hemoglobin, the red molecule inside blood cells that carries oxygen around the body. Outside the protective environment of the red cell, hemoglobin can be toxic.

Hemoglobin normally changes color from red to claret as it transfers oxygen around the body. However, when it is damaged the iron in hemoglobin is oxidized (like a car rusting) to produce dysfunctional brown and green products.

"Basically, hemoglobin produces free radicals that can damage the heart and kidneys," explained Professor Cooper. "The trick with artificial blood is to modify the molecule to be less toxic, but still perform the vital role of carrying oxygen around the body. No one has managed this yet."

"Professor Chris Cooper showing the changes in blood color. (Credit: Image courtesy of University of Essex)"

Source: University of Essex