Effect of saturated/unsaturated phosphatidylcholine ratio on the stability of liposome-encapsulated hemoglobin

The influence of different combinations of saturated and unsaturated phosphatidylcholines (PCs) as well as addition of alpha-tocopherol on lipid peroxidation and particle size change was analyzed. Because unsaturated egg PC was susceptible to peroxidation, partially hydrogenated egg PC or hydrogenated egg PC (H-PC) was frequently used instead of egg PC. The efficacy of another alternative with combinations of saturated and unsaturated PCs was investigated. Oxidation can be inhibited by adding alpha-tocopherol in the lipid formulation or by using different combinations of H-PC and PC. Adding alpha-tocopherol was shown to cause physical instability of liposomes, and increase the possibility of aggregation. Increasing the H-PC content in the liposome formulation will effectively reduce the peroxidation. The stability of liposome was dependent on both alpha-tocopherol and H-PC to PC ratio. Encapsulating hemoglobin in the liposome would promote the lipid peroxidation. (C) 1998 Elsevier Science B.V. All rights reserved.