The influence of phytosterols on the encapsulation efficiency of cholesterol liposomes

Lecithin vesicles, prepared by the dehydration-rehydration (DR) method, were used to encapsulate bovine serum albumin (BSA). These were used to test the feasibility of making liposomes containing phytosterols, such as beta-sitosterol and stigmasterol, as a substitute for cholesterol. Their physicochemical properties such as encapsulation efficiency (EE), stabilities of storage, pH, and oxidization were investigated to assess substitutability. Liposomes prepared with phytosterols or cholesterol exhibited higher EE for BSA than those prepared without the addition of sterols. In addition, the EE of liposomes was increased with repeating a DR cycle five times. Liposomes at pH 6 or 7 were most stable, irrespective of phytosterols or cholesterol being added. Liposomes stored at 4 degreesC had a higher residual percentage than those stored at -20 degreesC or room temperature. The addition of sterols to liposomes was effective in decreasing thiobarbituric acid-reactive substances (TBARS) during storage periods; the antioxidation was more marked when alpha-tocopherol was added to liposomes. The results indicate that replacing cholesterol with phytosterols in preparing liposomes is feasible and recommended.