Synthesis and characterization of artificial red cell (ARC)

Liposome-based red cell substitutes are very interesting because of their similarity in structure to red blood cells. Liposomes encapsulate not only Hb but also various regulators, so that they are able to share multiple functions like red blood cells. The author has succeeded in synthesizing such artificial cells by encapsulating an Hb solution with polylipid (stabilized bilayer membrane). This paper describes the synthesis, characterization and oxygen-transporting ability of this polylipid-based artificial red cell (ARC). Polylipid-encapsulated Hb was prepared by encapsulation of COHb under mild conditions, polymerization and decarbonylation. The average diameter was 0.2 μm and the distribution was sharp. The oxygen-transporting ability in vitro was as follows: P₅₀: 30-40 mmHg, OTE: 40%, n: approximately 2, [Hb]: approximately 10 g/dl, metHb: <5%. The viscosity was low (approximately 8 cP at 37°C) and the low colloidal osmotic pressure (0.1 mmHg/g/dl) could be adjusted to normal by adding human albumin. Polylipid/Hb microparticles were physically stable and the suspension could be frozen. After thawing, no changes in physical properties and oxygen-transporting ability were noted and no leakage of Hb. The product could be stored in the frozen state longer than six months without any change in quality. Polylipid/Hb is an artificial red cell based on stable liposomes, and its excellent properties demonstrate its high potential as a red cell substitute.