Tocopherol-phospholipid liposomes: maximum content and stability to serum proteins

This study addresses two questions: 1) what is the maximum amount of tocopherol that can be contained in egg phosphatidylcholine liposomes, and 2) what is the stability of these vesicles in the presence of serum proteins? These liposomes, made with a French pressure cell, can contain no more than 33 mol% of tocopherol. Tocopherol changes liposomes in a manner similar to cholesterol, making them larger, less permeable to aqueous dyes and highly resistant to protein-induced disruption. The suppression of protein-induced disruption is more pronounced with tocopherol than with cholesterol, even at lower molar ratios. Thus, liposomes containing alpha tocopherol (15 to 30 mol%) may be useful for delivering physiological quantities of this vitamin to cells in culture or to tissue in vivo.