Artificial blood : the 21st-century challenge

Currently, the race to find a suitable blood substitute is a major challenge in transfusion medicine. While pharmacological alternatives such as recombinant growth factors have been widely developed and of great use, blood substitutes similar to haemoglobin in terms of oxygen and carbon dioxide transport remain a challenge (Fig 1). Successful innovation in this field would enable blood substitutes to be stored on a shelf over longer periods, and infused safely at any time and in any place, regardless of the blood group, and would have a sufficient half-life in the circulation. Research in this field has benefited from development of new technologies in protein engineering, but overcoming the physiological mechanisms remains a challenge. Clinical trials are in progress to ascertain the safety and efficacy of current and newly developed blood substitutes or artificial oxygen carriers.

Quest for a blood substitute In order to appreciate the need for viable blood substitutes, it is important to consider several factors. Transfusion medicine, despite all the advancements in pharmacological alternatives to blood substitutes, faces problems that require further research. 

Shortage is a very important limitation, especially during disasters, war, emergencies, donor deferral and in countries with high infection rates. Religious or cultural beliefs necessitate the availability of alternatives for patients who might refuse blood transfusion. There is also disease transmission involving human immunodeficiency virus (HIV), hepatitis B virus (HBV) and hepatitis C virus (HCV), for example; these are pathogens associated with transfusion. A short shelf life leads to wastage of blood, rare blood groups can be a problem in a situation where there is a large demand, and immunological incompatibility represents a significant problem in patients who have antibodies and produce an adverse reaction to transfusion.