Different stabilities of liposomes containing saturated and unsaturated lipids toward the addition of cyclodextrins

Liposomes composed of unsaturated lipids were more stable than those containing saturated lipids toward DMe-beta-CDx, DMe-alpha-CDx and DMe-beta-CDx. The Hill coefficient values (n) indicated that the saturated lipid.DMe-CDx complexes had stoichiometric ratios in the range of 1 : 3-1 : 4, while the unsaturated lipid.DMe-CDx complexes had ratios in the range of 1 : 1.5-1 : 3. That is, a cis alkene group in the unsaturated lipids prevented complexation with a second DMe-CDx in the direction toward each acyl chain. Furthermore, the liposomes composed of the unsaturated lipids were much slower to form precipitates upon the addition of alpha-CDx than those of the saturated lipids. To the best of our knowledge, this is the first example showing that CDxs interact with unsaturated lipids.