Cytolytic activity of liposomes containing stearylamine

In order to develop the cytotoxic liposome, the cytolytic effect of polycationic liposome was examined. Upon incubation of the stearylamine-containing liposome (stearylamine-liposome) with rabbit erythrocyte, a significant extent of hemolysis was observed. Hemolytic activity of the liposome depends on the amount of stearylamine in the liposome membrane. The plots of the initial rate of hemolysis versus the concentration of stearylamine-liposome showed a sigmoidal curve, suggesting that stearylamine-liposomes act cooperatively on the erythrocyte membrane. Hemolytic activity of stearylamine-liposome was markedly influenced by the composition of hydrocarbon chains of the phospholipids in the liposome membrane, suggesting that the membrane fluidity of stearylamine-liposome is important to evoke the hemolysis. Since the liposomes containing acidic phospholipids inhibited markedly the stearylamine-liposome-caused hemolysis, it is likely that the primary target of stearylamine-liposome is the negatively charged component(s) such as acidic phospholipids on the erythrocyte membrane. Furthermore, stearylamine-liposome induced the release of the intravesicular contents from the liposome made of acidic phospholipids but not from the liposome made of phosphatidylcholine only. These results suggest that stearylamine-liposome interacted with the negative charges of the erythrocyte membrane and eventually damaged the cell. Erythrocytes from rabbit, horse and guinea pig are highly susceptible to stearylamine-liposome but those from man, sheep, cow and chicken are less so.