Chapter 49 - Red Blood Cell Substitutes

Abstract

Hemoglobin molecules extracted from red blood cells are modified by microencapsulation or crosslinking. This stabilizes the hemoglobin molecules and also allows the sterilization of the products to remove HIV and other microorganisms. A number of modified hemoglobins have been developed and clinical trials have been carried out. The results of these clinical trials have led to the elimination of a number of modified hemoglobins, leaving polyhemoglobin and conjugated hemoglobin. Two types of polyhemoglobin have been most extensively studied in Phase III clinical trials. These results have led to South Africa and more recently Russia’s approval of the routine clinical use of one type of polyhemoglobin. These decisions are based on their risk/benefit analysis for their own requirements. In North America and some other countries the requirements are such that they have not yet approved this product for routine clinical uses until further improvements have been carried out. New generations of modified hemoglobin are being actively developed. These include soluble nano dimension complexes of the following: Oxygen carrier with antioxidant properties (polyhemoglobin-catalase-superoxide dismutase and synthetic mimics of this); combined oxygen and carbon dioxide carriers with antioxidant properties (polyhemoglobin-catalase-superoxide dismutase-carbonic anhydrase); oxygen carrier with platelet-like properties (polyhemoglobin-fibrinogen); nano dimension artificial red blood cells with lipid or biodegradable polymeric membrane and others.