Blood is life’s elixir; it carries oxygen from your lungs to all the cells in your body, and picks up the carbon dioxide that you do not need to return it to your lungs so you can exhale it. It delivers nutrients from your digestive system and hormones from your endocrine system to the parts of your body that need them.
Moreover, blood passes through the kidneys and liver; it removes or breaks down wastes and toxins. Immune cells in your blood also help prevent and fight off illnesses and infections. Blood can also form clots, preventing fatal blood loss from minor cuts and scrapes.
Unfortunately, there are several challenges that can make it difficult or impossible to get patients the blood they need when they need it. Human blood has to be kept cool, it has a shelf life of 42 days; doctors must also make sure the blood is the right type—A, B, AB, or O—before giving it to a patient. If a person receives the wrong type of blood, a deadly reaction can result; moreover, the number of people who need blood is growing faster than the number of people who donate blood. Can artificial blood be the solution?
Artificial blood is a product made to act as a substitute for red blood cells. While true blood serves many different functions, artificial blood is designed for the sole purpose of transporting oxygen and carbon dioxide throughout the body. Depending on the type of artificial blood, it can be produced in different ways using synthetic production, chemical isolation, or recombinant biochemical technology.
Unlike real blood, artificial blood can be sterilized to kill bacteria and viruses; doctors can also give it to patients regardless of blood type. Many current types have a shelf life of more than one year and do not need to be refrigerated, making them ideal for use in emergency and battlefield situations. Therefore, even though it does not actually replace human blood, artificial blood is still doing great.
Research classified several specific blood substitutes in two classes: Hemoglobin-Based Oxygen Carriers (HBOCs), and Perfluorocarbons (PFCs). Some of these substitutes are nearing the end of their testing phase and may be available to hospitals; others are already in use. For example, an HBOC named Hemopure is currently used in hospitals in South Africa, where the spread of HIV has threatened the blood supply. On the other hand, PFC-based oxygen carrier named Oxygent is in the late stages of human trials in Europe and North America.
HBOCs vaguely resemble blood; they are very dark red or burgundy, and are made from real, sterilized hemoglobin, which are from a variety of sources such as Red Blood Cells (RBCs) from real, expired human blood; RBCs from cow blood, genetically modified bacteria that can produce hemoglobin and human placentas.
The challenge in creating a hemoglobin-based artificial blood is modifying the hemoglobin molecule. Various strategies are employed to stabilize hemoglobin; this involves either chemically cross-linking molecules or using recombinant DNA technology to produce modified proteins.
Unlike HBOCs, PFCs are usually white and are synthetic. They are a lot like hydrocarbons—chemicals made entirely of hydrogen and carbon—but they contain fluorine instead of carbon. Doctors primarily use PFCs in conjunction with supplemental oxygen as PFCs are chemically inert, but they are extremely good at carrying dissolved gases. They can carry 20%–30% more gas than water or blood plasma, and if more gas is present, they can carry more of it.
PFCs have two significant hurdles to overcome before they can be utilized as artificial blood. First, they are not soluble in water, which means to get them to work they must be combined with emulsifiers—fatty compounds called lipids, that are able to suspend tiny particles of perfluorochemicals in the blood. Second, they have the ability to carry much less oxygen than hemoglobin-based products; this means that significantly more PFC must be used.
Medical research never ceases to find solutions for fixing or replacing harmed organs; however, one might have never thought that our blood could be replaced. Blood is essential for survival; developing artificial blood offers another chance for survival for many patients. It seems that in this era of medical advances, everything is possible.
References
howitworksdaily.com
ncbi.nlm.nih.gov
science.howstuffworks.com
the-scientist.com
This article was first published in print in SCIplanet, Autumn 2014 Issue "How Things Work".
Cover image by Freepik