In order to prepare Hb-vesicles having a high oxygen-transporting ability, it is important to encapsulate concentrated Hb with a mixed lipid membrane having low lamellarity (n). The concentration of Hb in the Hb-vesicles ([Hb]in) increased with the Hb concentration used for the preparation of Hb-vesicles. Hb-vesicles with smaller lamellarity could be obtained by lowering the preparation temperature. The encapsulation of Hb was significantly influenced by the ionic strength and the solution pH because lipids and Hb are electrolytes. The lamellarity decreases with increasing solution pH because of electrostatic repulsion between the surfaces of lipid membranes. On the other hand, [Hb]in increases when the solution pH is lowered below the p/ of Hb (7.0 at 25°C) due to electrostatic interaction between Hb and the surface of the membrane. This interaction decreases with the ionic strength of the Hb solution, leading to a lower [Hb]in.
ASJC Scopus subject areas