Major limitations in the use of liposomes for oral formulation relate to their physical and chemical instability in the GI tract. In this study, the conjugate (PAA-DSPE) of poly(acrylic acid) and distearoylphosphatidylethanolamine (DSPE) was synthesized, and liposomes were prepared with the mixture of PAA-DSPE and DSPE to improve the stability of liposomes in the GI tract. The prepared PAA-DSPE was characterized by FT-IR and 13C-NMR to confirm the coupling between PAA and DSPE. In the elemental analysis, the coupling ratio of PAA and DSPE in PAA-DSPE was calculated as 1:1.73. The average size of a PAA-DSPE/DSPE liposome, measured by dynamic light scattering, was in the range of 300-500 nm, and the minimum average size was 320 nm at 6 mol% of PAA-DSPE. The stability of the prepared liposomes was evaluated in different pH (2, 5, 7.4) solutions, and in different concentrations of bile acid (0, 0.1, 1, 10%) and pancreatin solutions (0, 0.03, 0.3, 3%). The stability of liposomes in different conditions was determined by measuring the fluorescence intensity of 5(6)-CF leaked from liposomes. The amount of the 5(6)-CF leakage from the PAA-DSPE/DSPE liposomes of 6 mol% PAA-DSPE was the lowest in all the cases of acidic, bile, and pancreatin solutions. In conclusion, the optimum amount of PAA-DSPE in liposome was 6 mol%, and PAA-DSPE/DSPE liposomes could improve the stability in the GI tract.
- Bile solution
- Pancreatic solution