Synthetic or artificial blood works primarily through passive diffusion. This process takes advantage of the tendency of a gas to move from areas of greater concentration to areas of lesser concentration until it reaches equilibrium. In humans, oxygen shifts from the lungs (high concentration) to the bloodstream (low concentration). When blood reaches the capillaries, the oxygen then moves from the blood (high concentration) to tissues (low concentration).
Synthetic blood is not a full substitute for blood. While true blood serves a number of functions, synthetic blood is designed only to transport oxygen and carbon dioxide throughout the body. This form of synthetic blood is referred to as a “hemoglobin-based oxygen carrier.” HBOCs utilize hemoglobin, a natural oxygen-carrying molecule, to carry oxygen throughout the body. However, because the hemoglobin used in synthetic blood is not located inside a human’s red blood cells, it is susceptible to accumulating high toxicity levels. As a result, no form of HBOC synthetic blood has been approved by the Food and Drug Administration for use on humans, (HBOC-201 is FDA-approved for use in dogs) as of October 2014.
Scientists continue to work on perfecting synthetic blood because of the numerous benefits HBOC’s possess relative to blood transfusions. Some key benefits of HBOC’s compared to blood transfusions include faster and better oxygen distribution, no prior planning needed, universal compatibility, longer shelf life, no equipment required (including refrigeration) and no waste production.