mPEG Phospholipids
Polymers are often incorporated into liposomes to improve various properties of drug delivery vehicles. Polyethyleneglycol (PEG) is the most commonly used polymer in clinical practice. The methoxy form of PEG (mPEG) is usually used for conjugation applications due to the single hydroxyl group that can be coupled with several other groups including small drugs, proteins, polymers, and lipids. This conjugation results in stealth shielding and increased circulation times. The hydrophilic chains of mPEG conjugated liposomes create a barrier and reduce the interactions that the liposome is able to have with the reticular-endothelial system. In addition, pegylation increases the hydrodynamic size of the drug delivery system and therefore increases the clearance time. PEG-coating of liposomes is generally achieved by using mPEG-phospholipids to generate liposomes known as stealth liposomes (SLs).
Pasut G., Paolino, D., Celia C., Mero A., Jospeh A., Wolfram, J., Cosco D., Schiavon O., Shen H., Fresta M. (2015) Polyethylene glycol (PEG)-dendron phospholipids as innovative constructs for the preparation of super stealth liposomes for anticancer therapy. J. Con. Rel. 199:106-113