Liposomes preparation and drug encapsulation

In this work, sterically stabilized liposomes (stealth) were prepared from DPPC/Chol/PEG-PE at the molar ratios 100:20:4, respectively. The lipids were dissolved in chloroform and then deposited from organic solvent in a thin film on the walls of the round bottom flask of the rotary evaporator under reduced pressure and nitrogen gas. Ammonium sulfate (250 mM at pH 4) was then added to hydrate the dried thin film in the flask and kept in the water bath at 55 °C for hydration. To get small vesicles, the suspension is sonicated under temperature control for a period of 2 h. The sample was then gently poured on a surface of the gel chromatographic column packed with sephadex G-75 for the removal of un-entrapped ammonium sulfate.

Doxorubicin Hydrochloride (DOX) of 10 mg was dissolved in 5 ml HEPS buffer at pH 7.4and then added to the liposome suspension that eluted from the gel column at a concentration of 1 mg DOX/10 mol. of phospholipid. The liposomes - DOX mixture was incubated in water bath of a rotary evaporator for 1 h at 55 °C under reduced pressure. Post incubation period, the sample was passed again in the gel column to remove non-encapsulated DOX. The drug loading took place by the pH gradient method [26].