Cationic liposomes interact with negatively charged glycoproteins on the cell surface, thereby increasing the affinity and residence time with the target cells, resulting in increased drug delivery. Polyethylene glycol (PEG) is a kind of sterically-stabilized, hydrophilic polymer, has been used to improve liposome stability and enhance their circulation times in the blood. Adding PEG to a neutral liposome will protect the liposomes from circulating proteins, improving their plasma clearance and enhancing their therapeutic effects.