Sephadex g 50 gel columns

Egg phosphatidylcholine (EPC), soy phosphatidylcholine (SPC), hydrogenated soy phosphatidylcholine (HSPC), 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), 1,2-disteoroyl-sn-glycero-3-phosphatidylcholine (DSPC), and 1,2-distearoyl-snglycerophosphoethanolamine poly(ethylene glycol)₂₀₀₀ (DSPE-PEG-2000) were obtained from Avanti Polar Lipids, Inc. (Alabaster, AL). Cholesterol and barbituric acid were purchased from Sigma-Aldrich (St. Louis, MO). Liposomes were formed by the lipid film hydration method as described [28 (link), 31 (link)]. In brief, 25 mg of lipid mixture dissolved in chloroform was dried, and the resultant thin film was hydrated using 1 ml BA at 20 mg/ml and pH 7.3 to form multilamellar vesicles. The mixture was then annealed at 55–65 °C according to the type of PCs, sonicated, and subsequently extruded through stacked polycarbonate filters. DOX at 2 mg/ml was remotely loaded via sonication after extrusion. Liposomes were then filtered through Sephadex G-50 gel columns (GE Healthcare Life Sciences, Pittsburg, PA) to remove unloaded compounds, and stored at 4°C prior to use. The size (z-average) and heterogeneity in size (polydispersity index, PDI) were measured in PBS at room temperature by dynamic light scattering using a Nanosizer ZS90 (Malvern Instruments, Southborough, MA).