Interaction between a novel amphiphilic polymer and liposomes

We synthesized a novel amphiphilic polymer consisting of octadecylacrylamide and N,N-dimethylacrylamide with a molar ratio of 99 : 1. The polymer-induced aggregation of liposomes in an adequate lipid/polymer ratio. However, calcein, a water-soluble fluorescent dye entrapped in the large unilamellar liposomes (LUVs) did not leak out significantly although hydrophobic residues of the polymer penetrated into the lipid bilayer. Liposome aggregates by the polymer could be easily collected by low-speed centrifugation for 10 min at 1400×g and no significant leakage of the entrapped calcein inside the liposomes was observed. Dynamic light scattering (DLS) measurements showed that liposomes were enlarged in apparent particle size being coated with the polymer or aggregated by cross-linking. The polymer-coated liposomes were more stable against the detergent than the liposomes without a polymer coating.