Distearoyl sn glycero 3 phosphocholine dspc

Lipids used in the preparation of liposomes include 1,2-distearoyl-sn-glycero-3- phosphoethanolamine-N-[amino (polyethylene glycol)-3400] (DSPE-PEG(3400)- NH2) (Laysan Bio, Inc.), cholesterol (Sigma), and 1,2-distearoyl-sn-glycero-3- phosphocholine (DSPC) (Avanti polar lipids, Inc.). PEG-containing liposome (lipoPEG) was prepared by dissolving cholesterol (5 mg), NH2-PEG-DSPE (2 mg), and DSPC (10 mg) in 1 mL of chloroform in a round-bottom (RB) flask. The mixture was evaporated in a rotary evaporator under vacuum to make a thin layer of molecules in the RB flask. The lipid layer was hydrated by the addition of 1 mL double distilled water sonicated for 30 min to obtain a turbid liposome solution. The solution was frozen and lyophilized to obtain solvent-free dry liposomes. [Pyr1]-apelin-13 was encapsulated by hydrating the liposomes (17 mg) with 3.3 mg of pyroglutamyl [Pyr1]-apelin-13 in 1 mL double distilled water followed by 30 min sonication. In order to get the maximum encapsulation, the mixture was frozen and lyophilized again followed by rehydrating it with 1 mL double distilled water and sonicated before use. Hereby, liposome-PEG-[Pyr1]-apelin-13 (lipoPEG-PA13) was prepared.