Regulation of Properties of Lipid Membranes by Interaction with 2-Hydroxypropyl β-Cyclodextrin: Molecular Details

The interaction between 2-hydroxypropyl β-cyclodextrin (HPCD) and a liposomal bilayer has been studied. The main binding sites of HPCD on the surface of neutral liposomes based on dipalmitoylphosphatidylcholine (DPPC) are the phosphate groups of lipids. The complex formation with HPСD leads to the stabilization of the gel state of monocomponent liposomes. The inclusion of the anionic component, cardiolipin (CL, 20%), in the bilayer changes the nature of the liposome-HPCD interaction. The observed lipid disorder disturbs membrane integrity, which is revealed in the release of the included dye (phenolphthalein). The effect of HPCD on the process and parameters of the phase transition of anionic liposomes has been studied using thermograms, which show the change in the position of the absorption bands of lipid acyl chains in the FTIR spectrum of liposomes. A stratification of DPPC/CL (80/20%) bilayer into two microphases with different cardiolipin content has been detected. HPCD causes the more pronounced stratification in the bilayer, i.e., membrane destabilization near the melting point of CL-rich microphase and, vice versa, a decrease in the lipid mobility in regions with a low CL content. We have studied the effect of HPCD on the interaction of an antibacterial drug, levofloxacin (LV), with the lipid bilayer. It has been found that the complexation of the drug molecules with HPCD leads to an increase in the efficiency of drug adsorption on the surface of the bilayer. This may facilitate the transport of the drug through the bilayer due to the formation of defects in the membrane. LV in the complex with HPCD shows a high antibacterial efficiency in vitro against E. coli, which is not lower as compared with free LV.