Imagine a world with no blood transfusions. Millions would be lost to war, sickness, and surgery just because they were unable to receive fresh blood. Without the research carried out by two biochemists, Staurt Mudd and Earl Flosdorf in the early 1930’s at the University of Pennsylvania, this might have been the case. Their research was devoted to the drying and packaging of human blood serum, a medical technique that was developed and used in World War II as a way to collect blood, specifically in the United States for export to Britain. Although this technique was developed in Philadelphia, its impact was felt worldwide and was crucial to saving millions of lives during the war and even today is put to use in a variety of applications.
In one of its first applications, dried blood was used in agriculture as a fertilizer in the early 1900s. The blood was allowed to coagulate, then the clotted blood was separated out and dried, it was pulverized and directly applied to the ground. It was not until December of 1933 that Staurt Mudd, native to Bryn Mawr, Pennsylvania and Dr. Earl W. Flosdorf at the University of Pennsylvania prepared the first dried human blood. These methods remained unperfected until the 1940s, when they became necessary for World War II Military programs. The findings of Flosdorf and Mudd in Pennsylvania, along with the contributions of Ronald Greaves in England were largely responsible for the development of large scale applications of freeze drying.
The problem of transporting blood over long distances to help in the fight overseas lay in the fact that blood is a composition of many proteins that eventually breaks down under normal environmental conditions. Proteins are the basis of all living material and life itself is maintained through the building and breaking of these molecules. Biological proteins outside of the living organism aggregate and become insoluble, a sequence of events known as denaturation. Denaturation is influenced by time and temperature, and is a variable process dependent on the type of protein(s) involved. The problem with the commercial drying techniques available in the 1930s was that application of heat destroyed crucial proteins in blood, due to denaturation. Therefore, different methods needed to be developed, specifically for blood and biological materials.
In short, the process developed by Mudd and Flosdorf was a method of drying by sublimation after “high speed vertical spin freezing,” followed by a secondary desiccation. Now you may be saying to yourself, “Wait a minute, sublimation, desiccation… what?!” Simply put, blood is separated into its components, frozen, and dried twice so that there is less than 0.5% water left in the blood sample. This manner of drying blood is preferred over other methods since it leads to little or no protein denaturation, or degradation. This happens because the proteins are dried by sublimation, or the transition from a solid directly to a gas without transitioning through the intermediate liquid phase. This process removes the water from the frozen state blood without multiple transitions in temperature and time which is the cause of minimal degradation to the proteins in blood.
When war broke out in 1939, it seemed that blood transfusion would play an important role in the treatment of casualties. The problem with this was that whole blood, unless given fresh, needed to be refrigerated, and even then could only be used for a limited time after collection. In addition to this, the use of whole blood for transfusion in the field was limited due to the necessity for cold storage. Therefore, the conditions of war demanded a blood derivative that was stable, transportable, and suitable for administration to any patients.
The methods Flosdorf and Mudd developed out of a laboratory curiosity in 1935 and finally 10 years later in 1945, grew into a workable procedure. The techniques to carry out the high vacuum drying by sublimation involve two stages. In the first, ice is evaporated from a frozen state. In this stage heat is introduced to the frozen material very rapidly so that it does not soften or melt, which would occur in a slower process. At the same time the heat introduced will create gas which will need to be removed with a maximal flow of air away from the solid. Two common methods to carry out the first step involve condensation at a low temperature with condensers chilled with dry ice or refrigerants such as Freon. The second method uses high capacity steam ejectors for direct pumping and evacuation of vapor. Both methods need to occur at -9° to -12°C with regards to drying blood. In the second and final stage, the moisture is removed from the final dry solid to further reduce the residual content. This step is carried out at -40°C and involves another heating step which is not as strict in its execution as the first step since the remainder of water being evaporated is so small. Although Mudd and Flosdorf made major contributions to the process, other work was occurring overseas at the same time.
Ronald Greaves worked in the Blood Drying Unit in Cambridge, England and worked to perfect the process of blood drying in a pilot plant, a drying plant for large scale work and war-time difficulties. To carry out this process, first, serologic studies were performed on each blood donation. Then the blood was separated from the cellular elements in centrifuges. It was frozen in individual bottles via rotation in a cooling medium. Using this process, the blood could be desiccated from the frozen state under a high vacuum for long periods of storage. The basic methods preferred by Greaves were nearly identical to those of Mudd and Flosdorf. A minor difference in the methods was with regards to chilling the condenser with an alcohol bath rather than dry ice, mainly for cost purposes. Another difference lay in the emphasis of centrifugal vacuum spin-freezing developed by Greaves and colleagues, which would become the industry standard. This technique involves freezing the plasma by spinning the bottles at a high speed in a sub-freezing chamber. This centrifugal action evenly spreads the plasma on the inner walls of the container until it is frozen. This gives the benefit of a more even layer and the frozen crystals are more finely divided, which allows for quicker reconstitution of the dried product. This method was more widely used in Canada and England.
The work by these three men developed standards for freeze drying methods by 1945 that became crucial parts of World War II blood and transfusion programs. The process blood goes through during its drying and storage is illustrated in Figure 1, in a service laboratory in Houston, Texas.
When these techniques were put into action problems arose regarding blood typing and the rejection of certain blood transfusions in soldiers. This paved the way to new studies into the components of blood and exactly how the body reacts when transfusions are performed. Therefore, the men who developed the process for drying blood for transfusions inspired others to further study this field and to work to completely understand the transfusion process and discover all of the components involved.
The development of drying blood has led to the use of this process for the preservation of many other biological products, including live viruses for use in vaccines, living bacteria, hormones, tissue extracts, antibiotics, such as penicillin, and even chemotherapeutics, or cancer therapy drugs. These techniques even became common in the food industry, specifically for milk, eggs, meat, vegetables, and fruit.
According to the National Institutes of Health, every year nearly 5 million people in the United States receive life-saving blood transfusions. These methods helped to save millions of lives, not only within Pennsylvania, nor even in the United States, but throughout the world. The practice of blood transfusion became crucial not only in the field of battle but also in civilian surgeries and transfusions for the sick. The variety of applications that this process has been used for is innumerable. These men have inspired other scientists to push the boundaries and open doors in the study of blood. Mudd and Flosdorf have made contributions to the scientific world far beyond the scope they ever could have thought of when one day their tinkering in the lab lead to the drying of human blood.