Features of the interaction between cyclodextrins and colloidal liposomes

Interactions in aqueous dispersion between dipalmitoyl phosphatidyl choline (DPPC) liposomes and dissolved cyclodextrins (CD) of different chemical compositions, respectively, were studied. Liposomal dispersions with small unilamellar vesicles (SUV) of monomodal size distribution were prepared and the physical stability of the vesicles both in the presence and absence of cyclodextrin was investigated. For the characterization of the kinetic stability of the dispersions under various conditions, size-distribution functions determined by photon-correlation spectroscopy (PCS) were used. The affinity of cyclodextrins to the liposomes was characterized by 'binding isotherms' determined under equilibrium conditions at 25 degrees C. Based on the quantity of the cyclodextrins bound to the DPPC bilayers, stability constants for the associates were estimated. The physical stability of the liposomes and the possible control of stability were also investigated.