Viable human blood substitute found?

Every three seconds, someone, somewhere in the U.S. needs a blood transfusion, and one in three people will need a blood transfusion in his or her lifetime. In developing countries, an average of 25% of blood in blood banks is contaminated. In the U.S. and Canada, about two percent of banked blood cannot be used due to expiration.

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The need for a viable source of usable blood is strong. For years, hematologists have longed for a suitable blood substitute, also known as a "synthetic oxygen carrier." An ideal blood substitute would eradicate the risk of disease transmission, most notably HIV and hepatitis; be compatible with all blood types; have a shelf life approximately four times that of donated human blood; and prove hugely beneficial in cases of trauma--at home or on the battlefield--as well as for transfusions during surgery.

The main component of red blood cells, hemoglobin is an iron-containing protein that transports oxygen from the lungs to the rest of the body. Initial attempts at creating a blood substitute from hemoglobin alone have been hampered by several factors. Unmodified hemoglobin breaks up and quickly is eliminated from the body, a process that can be toxic to the kidneys. Outside of red blood cells, hemoglobin causes narrowing of blood vessels and inflammation of surrounding tissue. In the absence of a compound found in human red blood cells that prompts the release of oxygen, the hemoglobin "hangs on" to oxygen and fails to deliver it to the cells.

While previous efforts to develop a human blood substitute have been unsuccessful due to toxicity issues, researchers at Texas Tech University Health Sciences Center, Lubbock, are attempting to develop what could be the world's first viable substitute for human blood, as scientists have been able to identify and then nullify the source of toxicity. The result is a substance expected to be compatible with all blood types and have a shelf life of at least 180 days, compared to 42 for donated human blood.

It is made up of bovine blood that provides an additional advantage over products developed from outdated human red blood cells or from perfluorochemicals, as bovine blood is more readily available and could be more cost-effective to use. Technicians modify the bovine hemoglobin, which does not need DPG (diphosphoglycerate) to release oxygen, with three chemicals--GSH (glutathione), ATP (adenosine triphosphate), and Adenosine--to overcome the other limitations of unmodified hemoglobin.

In clinical testing, the new "blood," called HemoTech, did not show the vasoconstriction and inflammatory toxicities that have hampered other substitutes. HemoTech produces markedly reduced platelet aggregation, one of the major complications associated with percutaneous coronary intervention (PCI) procedures. HemoTech also demonstrates the potential for preventing restenosis (narrowing of the artery), another potentially dangerous side effect of PCI.

"Our studies to date have shown that HemoTech is safe, effective, inexpensive to manufacture, and convenient to administer," maintains Jan Simoni, who has served since 1993 as the Blood Substitute Group Leader and associate professor of research in the Department of Surgery, where he co-invented HemoTech along with fellow researcher Mario Feola.

"It has no immunity or infectious virus implications and requires no blood testing, typing, or cross-matching. It can be stockpiled. HemoTech could potentially save millions of lives every year."

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