Effect of polyethyleneglycol (PEG) chain on cell uptake of PEG-modified liposomes.

The liposomalization and polyethyleneglycol (PEG) modification of antitumor agents prolongs their circulation in the blood and increases their accumulation in the tumor. It is expected that modification of the liposome surface with PEG-Lipid will prevent connection of liposome and tumor cell, so we examined the effect of PEG chain length and anchor length on liposome uptake into the tumor cell. It was obvious that modification of the liposome surface with PEG-Lipid did not prevent liposome uptake into tumor cells, but rather, promoted it. It was suggested that the increase in liposome uptake into the tumor cell was induced by modification of PEG-lipids with apparent stability. In other words, PEG 2,000-DPG, which had a high rate of residual PEG-Lipid on liposomal membrane depending on the re-uptake to liposomal membrane, met to this requirement.