Blood, not only provides life, but is the key source of oxygen delivery to the tissues and organs within the body. Successful blood transfusions have saved many lives during conditions where most or whole blood of an organism has been wasted away due to some accident or other mishap. Transfusion of small amounts of blood is very usual and doesn't experience any problems while large amount of blood transfusion can be a bit problematic. Since the whole blood content has a short shelf life span and there is always a possibility of the blood getting virally contaminated, scientists have taken a big step towards creating artificial blood which would be used in emergency operations and surgeries.
The creation of artificial blood was based on the property of haemoglobin to act as a substitute for blood without blood typing. Since the blood sugars, as the name itself depicts, are present on the surface of red blood cells and not on haemoglobin molecule, it could be used as a blood substitute in any patient. Moreover, the haemoglobin could be purified and then sterilized to store it for long periods, ranging around one year. Although, it was later found that the naturally occurring haemoglobin couldn't itself act as the sole substitute for blood and it was required to make some modifications within the molecule so that it would act as a perfect blood substitute. In the year of 1937, scientists demonstrated that haemoglobin when used as a blood substitute proves toxic to kidneys, though it accomplishes it task of oxygen delivery to the cells. Structurally, haemoglobin is a tetramer molecule which dissociates into dimers when it is present in blood. The formation of dimers could be harmful as in the kidneys where these dimers gets filtered, toxic accumulations may result.
To resolve these problems, two main approaches were taken into consideration. In the first approach, the aim was to create a haemoglobin molecule that would be entirely stable in the blood. In order to achieve this, haemoglobin was first purified and then cross-linked to connect lysine amino acids using simple chemical agents like glutaraldehyde. Out of the experimentation, two desired forms were obtained viz. polyhemoglobin, that contained numerous hemoglobin molecules linked into a larger complex, and cross-linked tetrameric hemoglobin, that contained specific crosslinks formed somewhere between subunits within the tetramer.
In a more advanced approach, knowledge of recombinant DNA biotechnology was applied. In this second approach, a modified form of haemoglobin was created that carried two hemoglobin subunits that were fused into one chain. The recombinant form of haemoglobin thus obtained formed a stable complex that had the similar tetramer nature as of the naturally occurring haemoglobin molecule. Though it differed in the terms of having two of the subunits covalently linked together.
In both the approaches, the product was large enough to prevent its filtering by the kidneys. Moreover, they seemed have retained its oxygen-delivering capabilities as possessed by the naturally occuring haemoglobin molecule.
Another approach is also there which consists of creation of a non-immunogenic red blood cell by encapsulation of haemoglobin inside some artificial containers, for instance, liposomes. A researcher, Thomas M. S. Chang has taken forward steps in this particular field of interest and has taken his work beyond natural materials. In his studies, he has tried to use biodegradable polymers for creation of haemoglobin nanocapsules. Several polymers, for example, polylactide and polyglycolactide are degraded into water molecule and carbon dioxide molecules when they enter human body that makes them a safe vehicle for encapsulation. Naturally, they are found to be more porous in nature than the lipids and are also depited as the stronger ones. Due to these properties, there is a requirement of less membrane material resulting into elevation in the hemoglobin content of the material with liposomes. Antioxidant enzymes, for example, superoxide dismutase, catalase, and metHb reductase may be selected and considered as a refinement for the process and to be included into the components that the capsule contains. Thus, the development in bionanotechnology sectors have opened new doors for better and novel therapeutic strategies. The creation of artificial blood forms has raised hopes for newer and better alternatives in the healthcare and medicine sector for saving millions of life through safe and healthy blood transfusions.
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