Extractability of the phospholipid envelope of magnetoliposomes by organic solvents

Magnetoliposomes, consisting of nanometer-sized superparamagnetic magnetite cores surrounded by a phospholipid bilayer, were subjected to extraction using various organic solvent systems, When chloroform or n-hexane were used, there was little change in the phospholipid/Fe3O4 ratio. In contrast, upon including short-chain alcohols to these extraction systems, the outer shell of the bilayer, comprising approximately two-thirds of the original phospholipid content, was entirely removed. The resistance to extraction of the inner leaflet is due to very strong forces, thought to be chemisorptive in nature, Preliminary experiments demonstrating the apolar character of the surface of the remaining monolayer are also presented. (C) 1996 Academic Press, Inc.