Introduction Research on liposomes as drug carriers for cancer treatment has been widely conducted. Liposomes are closed vesicles formed of phospholipids which are basic components of biomembrane. They can encapsulate the lipophilic drug within the lipid bilayer and the hydrophilic drug within the aqueous core. In addition, it is also possible to incorporate both types of drugs into the same liposome formulation 1. PEGylation of liposomes has been frequently used to efficiently deliver drugs to tumors. PEGylation has the ability to decrease uptake by reticuloendothelial system, prolong blood retention, decrease degradation by metabolic enzymes, and reduce protein immunogenicity 2, 3. Strategies utilizing this are known to be useful for passive and active targeting to tumor cells 2 4. In the conventional PEG modification method, PEG lipid is added before liposome formation pre-insertion. However, this method has the problem that PEG is also modified on the membrane