Incorporation of phytosterols in soy phospholipids nanoliposomes: Encapsulation efficiency and stability

The objective of this work was to determine the effect of the incorporation of plant sterols on the stability and encapsulation efficiency of soy phospholipids vesicles. Small, unilamellar liposomes were prepared using high pressure homogenization at pH 7. Two types of commercial plant sterol preparations were employed: a water and oil soluble. The model hydrophilic molecule used for encapsulation efficiency studies was ascorbic acid. The lipid vesicles were prepared with a total lipid concentration of 150 mg mL(-1), and plant sterols were incorporated at two different phospholipid/plant sterol mix ratios: 14/1 and 13/2 (g/g). All the liposomes obtained showed an initial monomodal size distribution with an average diameter between 115 and 150 nm (with a coefficient of variation <10%), depending on the preparation. Incorporation of plant sterols increased the vesicle size and their encapsulation efficiency, regardless of the method of preparation. Dilution of the vesicles in imidazole buffer with or without glucose showed a reduction in the encapsulation over time in all cases, with differences in stability depending on the method of preparation. This work clearly showed that, when preparing liposomes using high pressure homogenization, the presence of plant sterols affects their colloidal stability and encapsulation efficiency. (C) 2012 Elsevier Ltd. All rights reserved.