Effects of PEG Chain Length of Phospholipid with Covalently Attached Poly (Ethylene Glycol) (PEG) on the Macroscopic State of Liposomes

Abstract

The effect of PEG chain length of distearoyl-N-monomethoxy poly (ethylene glycol) -succinyl-phosphatidylethanolamines (PEG-DSPE) having the molecular weight of PEG of 1000, 2000, 3000, 5000 and 12000 on the macroscopic states of Liposomes was examined from the standpoints of liposome formation, particle size, surface potential and dispersibility. All the dipalmitoyl phosphatidyl-choline (DPPC) was able to contribute to the formation of liposomes, while not all the PEG-DSPE with longer PEG chain was utilized. The concentration of PEG-DSPE in the liposomal bilayer membranes decreased with increasing PEG chain length of PEG-DSPE. The particle size of liposomes containing PEG-DSPE decreased with increasing PEG chain length of PEG-DSPE except for PEG12000-DSPE. PEG12000-DSPE was likely to be adsorbed on the DPPC liposomal surface. The absolute value of the zeta-potential of liposomes decreased with increasing PEG chain length of PEG-DSPE. The dispersibility of liposomes containing PEG-DSPE was maintained at least 14 days although the |zeta-potential| of liposomes was decreased.