Formulation, Characterization and Optimization of Liposomes Containing Eicosapentaenoic and Docosahexaenoic Acids; A Methodology Approach

Omega-3 fatty acids (FAs) have been shown to prevent cardiovascular disease. The most commonly used omega-3 fatty acids like eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are highly vulnerable to oxidation and therefore, have short shelf life. Recent advances in nanoliposomes provided a biocompatible system for stabilizing omega-3 FAs. Several methods could be implemented to prepare nanoliposomes. To the best of our knowledge, the performances of these methods in preparation omega-3 FAs have not been examined. Nanoliposomes were prepared by thin film hydration followed by one of the following methods: 1- extrusion, ultrasonic irradiation; 2- bath sonication; 3- probe sonication; or 4- combined probe and bath sonication. The size of liposomes obtained from methods 1 to 4 were 99.7 ± 3.5, 381.2 ± 7.8, 90.1 ± 2.3, and 87.1 ± 4.10 nm with zeta potential being -42.4 ± 1.7, -36.3 ± 1.6, -43.8 ± 2.4, and 31.6 ± 1.9 mV, respectively. The encapsulation efficiency (EE) for DHA was 13.2 ± 1.1%, 26.7 ± 1.9%, 56.9 ± 5.2% and 51.8 ± 3.8% for methods 1 to 4, respectively. The corresponding levels for EPA were 6.5 ± 1.3%, 18.1 ± 2.3%, 38.6 ± 1.8%, and 38 ± 3.7%, respectively. The EE for DHA and EPA of liposomes for both methods 3 and 4 increased significantly (p<0.05). Propanal, as the major volatile product formed during liposomal preparations, amounts from 81.2 ± 4.1 to 118.8 ± 2.3 μg/Kg. The differential scanning calorimetry (DSC) study showed that DHA and EPA influence the phase transition temperature of small unilamellar vesicles (SUVs) of dipalmitoyl phosphatidyl choline (DPPC). Transmission electron microscopy (TEM) images of liposomes stained with uranyl acetate showed that the liposomes were spherical in shape and maintain high structural integrity. In conclusion, probe ultrasound of pre-formed liposomes facilitates significant loading of DHA and EPA into the nanoliposomal membrane.