Partition of polysaccharide-coated liposomes in aqueous two-phase systems.

Hydrophobized polysaccharides such as cholesterol-bearing pullulan (CHP), dextran (CHD) and mannan (CHM) effectively coat the liposomal surface. Partition of the hydrophobized polysaccharide-coated liposomes in an aqueous two-phase system (PEO (top)/pullulan (bottom) or PEO (top)/dextran (bottom)) was investigated (PEO = poly(ethylene oxide)). Conventional liposomes without a polysaccharide coat mostly locate at the interface between the two polymer phases. The polysaccharide-coated liposomes, on the other hand, were partly partitioned to the bottom polysaccharide phase depending on the structure of the hydrophobized polysaccharide on the liposomal surface. The affinity between the polysaccharide on the liposomal surface and that in the bulk bottom phase controls the efficiency of partition. The sequence of interaction strength between the two carbohydrates was the following: for the PEO/dextran two-phase system, dextran(liposome)-dextran(bulk) > mannan(liposome)- dextran(bulk) > pullulan(liposome)-dextran(bulk); while for the PEO/pullulan system, the sequence of interaction strength was pullulan(liposome)- pullulan(bulk) > dextran(liposome)-pullulan(bulk) approximately mannan(liposome)-pullulan(bulk).