Synthesis of Sulfated Cyclodextrin Amphiphiles with Liposomal Encapsulation Properties

Abstract

A novel class of amphiphiles with sulfate groups at the C-6 position and palmitoyl groups at the C-2, 3 positions of α- , β- , and γ- cyclodextrin (CD) were efficiently synthesized. These compounds formed stable monolayers with high collapse pressures at the air-water interface. The mixed monolayer behaviors of the 6-O-sulfated CD amphiphiles (SO 3 -CDC 16 ) in the presence of dipalmitoyl phosphatidylcholine (DPPC) and cholesterol were discussed using the surface pressure-molecular area (π-A) isotherms. The collapse pressures showed maxima at molar ratios of SO 3 -CDC 16 lower than 10 mol%. A morphological analysis of the liposomes containing DPPC and 4 mol% SO 3 -CDC 16 formed in PBS was carried out using transmission electron microscopy with negative staining, and vesicles with maximum diameters of 350-500 nm were observed. Moreover, the releasing ability of these liposomes was examined using a fluorescent compound, calcein. It was clearly shown that liposomes containing SO 3 -CDC 16 could release encapsulated calcein more easily than liposomes consisting only of DPPC, and that the release rate depended on the phase transition temperature of the SO 3 -CDC 16 included in the liposome membrane.