Cyclodextrin-Lipid Complexes: Cavity Size Matters

Lipids being hydrophobic or amphiphilic can be encapsulated by cyclodextrin complexation. Among the various groups of lipids cholesterol, fatty acids, phospholipids and sphingolipids are overviewed concerning the structural requirements for both the lipid and the cyclodextrin component of the complexes. The chain length and the number and position of the double bonds in the fatty acids, the polarity of the head-group in the phospholipids and sphingolipids are important factors. Concerning the cyclodextrins, in addition to the most crucial cavity size also the chemical microenvironment of cavity entrances determine the interaction with lipids. While fatty acids, phospholipids and sphingolipids prefer the alpha-cyclodextrin cavity, cholesterol is complexed first of all by the beta-cyclodextrin and its derivatives. Methylated beta-cyclodextrin has extreme affinity to all of these lipids, which are common constituents of cell membranes. Based on the knowledge on the specific cyclodextrin-lipid interactions, cyclodextrin derivatives are able to selectively remove certain lipid components from model and biological membranes and can be selected making possible to modulate the lipid profile in such membranes.