Nov. 7, 2014

By Medical Discovery News

In the series “True Blood,” the invention of artificial blood allows vampires to live among humans without inciting fear. In the real world, however, artificial blood would have very different effects, as 85 million units of blood are donated worldwide and there is always a demand for more. An artificial blood substitute free of infectious agents that could be stored at room temperature and used on anyone regardless of blood type would be revolutionary.

That is exactly what a group of scientists at the University of Essex in England are working on, although the search for an artificial blood substitute started 80 years ago. All red blood cells contain a molecule called hemoglobin, which acquires oxygen from the lungs and distributes it to cells throughout the body. Their plan is to make an artificial hemoglobin-based oxygen carrier (HBOC) that could be used in place of blood.

HBOCs are created using hemoglobin molecules derived from a variety of sources, including expired human blood, human placentas, cow blood, and genetically engineered bacteria. The problem is that free hemoglobin, which exists outside the protective environment of red blood cells, breaks down quickly and is quite toxic. Therefore, HBOCs are not approved for use in most of the world due to their ineffectiveness and toxicity.

The active group in hemoglobin that binds to oxygen is called heme, which can actually be quite toxic. Scientists have found a variety of ways to modify hemoglobin to increase its stability but safety issues still remain. If the hemoglobin’s processing system is overwhelmed, a person may develop jaundice, which causes the skin and whites of the eyes to turn yellow. Too much free hemoglobin can also cause serious liver and kidney damage. When free hemoglobins, not whole red blood cells, are infused, the human body’s natural system for dealing and disposing of this molecule is overwhelmed, leading to toxicity. That is why blood substitutes consisting of free hemoglobin have been plagued with problems, such as an increase in deaths and heart attacks.

But scientists involved in this latest effort to produce a blood substitute have been reengineering the hemoglobin molecule. They are introducing specific amino acids, which are the building blocks of proteins, into hemoglobin in an effort to detoxify it. Preliminary results indicate that this approach may work. They have already created some hemoglobin molecules that are much less reactive and are predicted to be less toxic when used in animals or people.

If successful, this HBOC would be a universal product, meaning it could be used on everyone and there would be no need to waste time on testing for blood types. It would also be sterile, free of any of the infectious agents that donated blood must be tested for. Instead of refrigeration, it could have a long shelf life at room temperature, perhaps years, so it could be stockpiled in case of major emergencies. It could even be kept on board ambulances and at remote locations far from hospitals. The search for an effective and nontoxic blood substitute is one the medical field’s Holy Grails, and if proven successful, these scientists may have finally found it.

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