Nucleopore polycarbonate filters

Caffeic acid derivatives encapsulated liposomes were prepared using the dry lipid film and extrusion method. A 1 mL solution of 10 mg of total lipids in chloroform (SPC:DSPE-PEG₂₀₀₀ 95:5 mol/mol) were mixed with 1 mg of caffeic acid esters in methanol. Subsequently, solvents were removed from the samples via evaporation under a stream of nitrogen-gas to form a homogeneous lipid film on the flask wall and dried for 2 h at low pressure using a Savant Modulyo lyophilizer (Thermo Fisher Scientific, Waltham, MA, USA). Then, the lipid film was suspended by addition of 1 mL of sterile normal saline (0.9% NaCl), with mixing, until it was completely hydrated. The liposomal suspensions were extruded 6 times through nucleopore polycarbonate filters (Whatman, Maidstone, UK) with pore sizes of 100 nm, using a Thermobarrel Extruder (10 mL Lipex extruder, Northern Lipids, Burnaby, BC, Canada). During the extrusion procedure, nonencapsulated compounds were separated from the loaded liposomes and were deposited on the surface of the polycarbonate filter. Empty liposomes without CA derivatives were prepared in the same manner. In the case of Nile Red loaded liposomes, 50 µL of Nile Red solution (1 mg/mL) was added additionally to the total lipids.