I started my career as a blood banker in 1973 and switched to pathology informatics in 1982. For this period of nine years, the idea of "artificial blood" was very hot, funded largely by the military. Obviously, the military has a keen interest in a blood substitute with long shelf life, no requirement for crossmatching, and no fear of disease transmission. Fast forward to the present time when the hope of a practical blood substitute has yet to be fulfilled. A recent article provided an interesting perspective on this topic (see: Another Step Closer to Artificial Blood). Below is an excerpt from it:
Researchers have created an artificial red blood cell that effectively picks up oxygen in the lungs and delivers it to tissues throughout the body. This artificial blood can be freeze-dried, making it easier for combat medics and paramedics to keep on hand for emergencies, said senior researcher Dr. Allan Doctor....It's a dried powder that looks like paprika, basically ....It can be stored in an IV plastic bag that a medic would carry, either in their ambulance or in a backpack, for a year or more. When they need to use it, they spike the bag with sterile water, mix it, and it's ready to inject right then and there. The artificial blood cell, which is about one-fiftieth the size of a normal red blood cell, is made from purified human hemoglobin proteins that have been coated with a synthetic polymer....The hunt for an artificial blood substitute has been underway for more than 80 years, but the closest prior attempts have failed in two major ways....Earlier versions could capture oxygen in the lungs, but then would not effectively release the oxygen after traveling out to tissues and organs....There also was an unintended reaction between "naked" hemoglobin and nitric oxide, a substance released by the lining of blood vessels that allows the vessels to relax and open up....The polymer coating also keeps the hemoglobin from reacting with nitric oxide in the bloodstream, thus preventing dangerous constriction of the blood vessels....There's also one more benefit -- because the polymer coating is "immune silent," the artificial blood can be used in anyone regardless of blood type....Lab tests involving mice and rats have proven that the artificial red blood cells can effectively deliver oxygen to needy tissues....Besides emergency settings, the artificial blood also could be used to help keep donated organs alive on route to a recipient....
The research on artificial blood continues unabated. What's interesting to me about the article about Doctor's research is that he has apparently come to the conclusion that it's extremely difficult to duplicate the function of human hemoglobin in terms of oxygen capture and release. He has thus wrapped hemoglobin with a synthetic polymer to prevent undesirable reactions between the "naked hemoglobin molecule" and the nitric oxide released by the lining of blood vessels. However, Doctor has bigger ideas in mind for his research than a blood substitute, although that would be a great gift for transfusion medicine. Here is an excerpt from his lab's home page:
[T[he long term goal of the studies in my lab is to define the role of red blood cells (RBCs) in the spread of vascular dysfunction during oxidative stress, as exemplified by the development of secondary lung injury. Impaired pulmonary vascular control occurs early in respiratory failure complicating systemic inflammation. This pulmonary vascular dysregulation is characterized by loss of coupling between regional vascular tone and oxygen gradients (e.g. ventilation – perfusion mismatching). While nitric oxide (NO) signaling has been implicated, there is no clear mechanism linking remote inflammation to downstream lung injury. New data suggest that NO groups circulate and signal remotely through serial NO-thiol transfer reactions.