Liposomes consisting of two different kinds of lipid were used in this study. Liposomes consisting of saturated fatty acids were composed of distearoyl phosphatidylcholine, distearoyl phosphatidyl ethanolamine, distearoyl phosphatidyl glycerol acid, and cholesterol in a 4:3:2:7 molar ratio (stearoyl liposomes), and liposomes consisting of unsaturated fatty acids were composed of dioleoyl phosphatidylcholine, dioleoyl phosphatidyl ethanolamine, dioleoyl phosphatidyl glycerol acid, and cholesterol in a 4:3:2:7 molar ratio (oleoyl liposomes). The crude liposome solution was passed through a membrane filter (nucleopore polycarbonate filter, Coster) with a pore size of 0.2 mm.