Artificial blood: one step closer
A group of American and Canadian researchers working under the leadership of Allan Doctor has developed artificial red blood cells that effectively absorb oxygen in the lungs and release it in all organs and tissues. Such artificial blood can be freeze-dried, stored in powder form and, if necessary, diluted with sterile water, which will greatly facilitate the task of emergency medical doctors.
According to experts, about 70% of deaths from wounds during military operations occur as a result of shock caused by blood loss, and not because of life-incompatible injuries to vital organs. Moreover, in the USA alone, about 20,000 seriously injured people die from blood loss every year before they are admitted to a medical institution.
The search for functional artificial blood has been going on for more than 80 years, but so far even the most successful options have not provided proper results for two main reasons. Earlier versions bound oxygen in the lungs, but could not effectively release it in tissues and organs. The second reason for the failures was an unintended reaction between hemoglobin and nitric oxide, a compound released by the inner lining of blood vessels that provides vasoconstriction and dilation. The protein hemoglobin, which is part of erythrocytes, not only provides the red color of these blood cells, but also performs the function of an oxygen carrier throughout the body. However, when it enters the bloodstream in its pure form, it absorbs nitric oxide, causing a sharp narrowing of blood vessels, leading to the development of heart attacks and strokes.
The solution to both problems proposed by the authors is that the artificial erythrocyte created by them, the size of which is approximately one-fifth the size of an ordinary erythrocyte, is made from purified human hemoglobin, after which it is covered with an artificial polymer.
Due to the chemical properties of the polymer coating, artificial red blood cells absorb oxygen in conditions of high pH (low acidity) of the lungs and release it in an acidic tissue environment. According to the Doctor, the relationship between affinity (affinity for oxygen) and the level of blood acidity allows artificial red blood cells to mimic the behavior of ordinary cells.
The polymer coating also prevents the reaction between hemoglobin and nitric oxide in the bloodstream, which prevents the contraction of blood vessels. In addition, due to its immunological neutrality, it provides the possibility of artificial blood transfusion to all patients, regardless of blood type.
The results of experiments on mice and rats, during which 70% of the animal's blood was replaced with artificial blood, confirmed the ability of artificial red blood cells to efficiently deliver oxygen to the tissues in need of it. Such animals were indistinguishable from animals that received transfusion of donated blood from individuals of the same species.
In addition to emergency medical care, artificial blood can be used to preserve the viability of donor organs on their way to the recipient, as well as as an addition to the stock of conventional donor blood products during complex surgical interventions, such as open heart surgery.
However, artificial red blood cells can never completely replace real blood. Firstly, at the current stage, the predicted period of life in the bloodstream for them is from half to a third of a day, whereas donor red blood cells can circulate in the recipient's body for about 120 days. The authors believe that over time, the life expectancy of artificial red blood cells will be increased to several days, but it is very unlikely that they will ever be able to approach the longevity of normal red blood cells.
In addition, the only function they perform is the delivery of oxygen, whereas normal red blood cells perform several other important tasks, such as antioxidant protection of tissues, regulation of blood flow, participation in the immune response, as well as in the formation of blood clots.
The developers warn that the results they have obtained are preliminary and before conducting clinical trials, artificial blood must be tested on rabbits and monkeys. Researchers have a lot of work ahead of them, which may take 10 years.
The results of the work of Dipanjan Pan et al. 1027 Erythromer (EM), a Nanoscale Bio-Synthetic Artificial Red Cell: Proof of Concept and In Vivo Efficacy Results were presented at the 58th Annual Congress of the Society of Hematology, held December 3-6, 2016 in San Diego, USA.
Evgeniya Ryabtseva
Portal "Eternal youth" http://vechnayamolodost.ru
12.12.2016