2.1. Preparation of liposomes

Liposomes were prepared by film hydration procedure. The lipids OO4 and DOPE were dissolved in chloroform/methanol (8:2, v/v) in a round bottom flask and mixed to a molar ratio of 1:3 (cationic lipid/phospholipid). The solvent was evaporated for 1 h at 200 mbar. Then, 150 mM of NaCl with 10 mM acetic acid at pH 4 was added to final concentration of 1 mg/mL. Afterward, the lipid dispersion was incubated at 50°C and shaking gently for 30 min at 1,400 rpm (Eppendorf Thermomixer 5436) followed by sonication at 37 kHz and 50°C for 5 min. 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine-N- (lissamine rhodamine B sulfonyl) ammonium salt (Avanti Polar lipids); Rhodamine-DOPE-loaded liposomes were prepared with the same method using a molar ratio of 1:3:0.05 (n_OO4:n_DOPE:n_{Rhodamine-DOPE}).