Synthetic Blood

Synthetic Blood is a substance that mimics and fulfills some of the functions of biological blood and provides an alternative to blood transfusion. Providing an alternative to blood transfusion is important because it helps reduce the risks of immunosuppression and disease transmission associated with blood transfusions, and it also addresses religious concerns.

Historically, there has always been a need for blood substitutes as long as people have had blood to lose. No significant progress was made in the development of blood substitutes until William Harvey discovered how blood circulates in 1616.. Soon after, people experimented  with blood substitutes such as milk, beer, animal blood, and even urine. In 1883, Ringer’s solution, which was composed of sodium, potassium, and calcium salts, could keep a heart pumping. Later research confirmed that the solution increased the volume of the blood. However, it is not a full substitute for blood because it does not transport oxygen to cells. Blood transfusion technology kept getting better and better with the discovery of blood types in 1901 by Karl Landsteiner and with the establishment of blood banks post World War II. In 1966, discoveries were made with mice that revealed a new blood substitute, perfluorochemicals. Research declined as the blood bank system was effective—until its limitations became apparent during the Vietnam War. The conflict produced renewed interest in blood substitutes that stretches into the modern day. 

There are multiple different types of synthetic blood. Most notably, there are perfluorocarbon based blood and hemoglobin based synthetic blood types. Each has its own purposes and treats different types of diseases. Perfluorocarbon based synthetic blood is unique in that it doesn’t mix with blood and so it makes up a small part of the actual substitute. Despite this, they are still incredibly useful as they transport oxygen, the main function of blood. Additionally, PFC particles are smaller and so they can get into vessels that have shrunk for whatever reason, enriching oxygen-deprived cells. PFC solutions are so efficient at transporting oxygen that mammals, including humans, can breathe fully submerged in them. This is a process known as liquid breathing. An additional benefit of PFC solutions compared to hemoglobin counterparts is that they are completely man-made as opposed to the hemoglobin based synthetic blood which needs modified hemoglobin. Hemoglobin-based substitutes gained interest because they are relatively straightforward to produce. You already have Ringer’s solution, you just need something to take the blood, and why bother making a new one when hemoglobin is right there, it's already being used in the body. However, raw hemoglobin is not as useful as a substitute because it merely transports oxygen without effectively delivering it to cells and has a short lifespan in blood vessels. Scientists have used multiple methods to overcome these flaws including genetic modification, cross-linking and polymerization.

Synthetic blood offers a promising solution to the global decline in usable blood for transfusions.. And with the multiple ways to make it, we don’t have to worry about relying on one type and running out of that either. Overall, synthetic blood will likely play a vital role in the future of medicine.

References:

Cushing, M. M. (n.d.). Forthcoming issues - critical care clinics. Retrieved from https://www.criticalcare.theclinics.com/article/S0749-0704(23)00084-2/fulltext 

Sarkar, S. (2008). Artificial Blood. Retrieved from https://pmc.ncbi.nlm.nih.gov/articles/PMC2738310/ 

Squires, J. E. (2002). Artificial blood | science. Retrieved from https://www.science.org/doi/10.1126/science.1068443