Layer-Controlled Hemoglobin Vesicles by Interaction of Hemoglobin with a Phospholipid Assembly

Hemoglobin vesicles, which encapsulated concentrated hemoglobin (Hb) with a bilayer of dipalmitoylphosphatidylcholine/cholesterol/palmitic acid, were prepared under various preparation conditions in order to decrease the number of bilayers ( n ) constructing the vesicle and increase the Hb concentration in the interior of the vesicle ([Hb] in ). n decreased when the surface potential of the bilayer became more negative because of the electrostatic repulsion between the bilayers, while with a changing ζ-potential of Hb from positive to negative, [Hb] in showed a precipitous fall because of the electrostatic repulsion between Hb and the surface of the bilayer. A temperature decrease leads to a quality increase in the Hb vesicles ([Hb]/[lipid]) in spite of the [Hb] in decrease by the viscosity increase of the Hb solution. This is explained by the effective reduction of n due to the reduction in membrane fluidity and the protonation of Hb.