Lipid nanospheres containing vitamin A or vitamin E:: Evaluation of their stabilities and in vitro skin permeability

To encapsulate a fat-soluble vitamin, lecithin composed of several hydrogenated phospholipids obtained from soybean and an adjuvant were used. The resulting lipid nanospheres were about 200-300 nm in size and had a monodispersed-size distribution. Increasing the proportion of the oil phase produced large lipid droplets. The size and zeta-potential of a lipid nanosphere containing a 10 w/w% oil phase decreased with an increased proportion of lecithin and then leveled off with a lecithin content of about 1.2 w/w%. Furthermore, an attempt was made to improve the stability of a lipid nanosphere consisting of vitamin and lecithin by coating the surface of the lipid layer with several emulsifiers that had different hydrophilic lipophilic balance (HLB) values and molecular weights. The lipid nanosphere emulsion prepared with only lecithin showed a significant coalescence over a storage period of 60 days. However, the size of the lipid nanosphere was smaller and its in vitro stability was significantly improved compared with other formula, when Tween 80 was used as the cosurfactant. in particularly, the lipid nanosphere with the minimum size and maximum stability had a 1:1 content ratio of lecithin to Tween 80. From in vitro permeation experiments using rat skin, it was found that the permeation of the vitamin from a lipid nanosphere was greater than that of free Vitamin A or E, and varied depending on the composition and size of the lipid nanosphere.