Critical molecular weight effects in the aggregation of phospholipid vesicles triggered by water-soluble polymers and an integrated glycolipid

The intervesicular aggregation of phospholipid vesicles is induced by the addition of water-soluble polymers such as poly(ethylene glycol), dextran, etc. due to the interaction between the vesicular surface and the water-soluble polymers. The interaction can be expressed by the critical molecular weight (M_c) of the water-soluble polymers for the aggregation of vesicles. The surface modification of vesicles with glycolipids (O¹,O⁵-bis(octadecyl)N-maltooligonoyl-L-glutamate) accelerates the aggregation of vesicles induced by dextran; therefore, M_c significantly decreased due to the surface modification. No dependence of phospholipid concentration and dextran concentration in an aqueous phase on the M_c indicates that dextran does not act as a cross-linking agent among the vesicles. A clear dependence of the density of the saccharide chains on the vesicular surface on the M_c suggests that dextran should adsorb on the surface of the vesicles by the interaction with the oligosaccharide chains on the surface and cause vesicular aggregation. A lower critical solution temperature was observed for this kind of interaction, and the critical temperature was controlled by changing the molecular weight of dextran.