Synthetic Blood Introduction

Introduction
     Artificial blood is anxiously awaited as the population, and thus the need for a life-saving blood, grows. More than 100 million pints of blood are transferred to individuals each year during surgery and emergency procedure. In America, 2 to 3 pints of blood are used every 3.7 seconds. Unfortunately, the blood supply has not been able to keep up with demand. In January of 1999, hospitals were faced with a blood draught. Many were forced to postpone non-emergency surgeries (Cannell, 1999). Donated blood also carries dangers such as disease and type specific antibodies. Whole blood also expires quickly (with a shelf life of 6 weeks at most). It is for these reasons that artificial blood has become an issue of such importance to the scientific community.
     In 1957, Dr. Thomas Chang began the first promising research regarding artificial red blood cells. Most of the successful projects involving synthetic blood products have stemmed from the research he did while trying to create synthetic cells. (For further information click here ). By 1985, the public had realized the potential of synthetic cells and was ready to support his search for a substitute for human blood.
     Since Chang’s initial efforts to create artificial cells, there have been three main research attempts to create a blood substitute, each funded by a pharmaceutical company with a major financial interest in the outcome. Although one of these projects was terminated as it reached its final stages, the other two show great promise, and their research continues.
    The company furthest along at the moment is called Biopure. They have created an artificial blood product called Oxyglobin, which has already been accepted for use in veterinary hospitals in the U.S. The first to be accepted for use, Oxyglobin is created when hemoglobin molecules are treated with glutaraldehyde, a chemical that binds the hemoglobin molecules together. This provides a stabilizing affect for the molecule, and prevents its decomposition into toxic dimers, a feat normally accomplished by the membrane of the red blood cell. (See The Hemoglobin Molecule for more information). Biopure researchers feel that Oxyglobin may even improve upon some aspects of human blood. The molecules of hemoglobin are much smaller than the red blood cells of human blood, and thus are more efficient when delivering oxygen into capillaries or around blood clots (Cannell, 1999). However, the size of the molecules also provides a disadvantage in its easy absorption by the body. Only half of the molecules will last more than twelve hours in the blood stream, compared to the 40 to 60 day range of a human red blood cell (RBC). There is much more research to be done before Oxyhemoglobin is allowed to be used in human hospitals; However, Biopure scientists are optimistic (Cannell, 1999).
    A second research team at Alliance Pharmaceutical Corporation in San Diego has used a more synthetic approach to the problem. A compound with fluorine and chlorine has been shown to absorb more oxygen then even hemoglobin. These men and women have proposed a blood substitute using these perfluorocarbons (PFC’s) instead of human hemoglobin. They claim that though PFC’s are 40 times smaller than RBC’s, they can carry twice as much oxygen twice as quickly due to absorption of the O₂ versus the actual bonding completed by the iron in the hemoglobin molecule. The PFC’s form an emulsion that acts as a sponge, soaking up the oxygen and releasing it easily at it designation. Although this particular project is not as far along as Oxyhemoglobin, it also shows promise (Cannell, 1999).
     The third research group, which has terminated its project, used a hemoglobin-based oxygen carrier they named HemAssist. In this case, human hemoglobin was cross-linked with an aspirin derivative to prevent its decomposition into toxic dimers (Waldspurger, 1998). The Hemoglobin was then suspended in an electrolyte solution. The project looked very promising, and reached Phase III trials (trials involving human patients) before it was discontinued due to a high mortality rate. Some doctors believe that the mixture caused vasoconstriction, constriction of blood vessels, in the patients, but the true cause of death is unknown (Cannell, 1999).
    Each of these projects has taken great strides in the quest to discover an effective replacement for human blood in emergency situations, yet a leading, effective solution has not been found. What is not known is a device, whether synthetic or biological that will provide fluid replacement for the circulatory system, carry adequate amounts of oxygen from the lungs to the body and carbon dioxide from the body to the lungs, and be stable enough to last long enough for the body to replace the blood lost. Until all of these criteria are met, real human blood must be used.

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