Effect of Lipid with Covalently Attached Poly(ethylene glycol) on the Surface Properties of Liposomal Bilayer Membranes

Abstract

The effect of lipid with covalently attached poly(ethylene glycol) (PEG−lipid) on the surface properties of liposomal bilayer membranes was examined from standpoints of particle size, surface potential, microviscosity, micropolarity, and permeability. The particle size and the absolute value of the ζ potential of liposomes decreased with increasing mole fraction of PEG−lipid. The permeability of PEG−liposomes was decreased as compared with regular liposomes. The microviscosity and the micropolarity of liposomal bilayer membranes showed a maximum and a minimum value, respectively, at 6 mol % of PEG−lipid. The packing state of liposomal bilayer membranes became rigid and the lipid bilayers were microscopically stabilized by the addition of PEG−lipid, and the optimum amount of PEG−lipid in liposomes was 6 mol %.