PEGylated "stealth" nanoparticles and liposomes

Through nanomedicine, game-changing methods are emerging to deliver drug molecules directly to diseased tissue. The targeted delivery of drugs and imaging agents via drug carrier-based platforms is among the most promising of these methods. Such drug delivery systems can now be synthesized from a wide range of different materials, made in a number of different shapes, and coated with an array of different organic molecules, including ligands. In this chapter, we will focus on PEGylated liposomes and nanoparticles. By grafting polyethylene glycol (PEG) polymers on the surfaces of liposomes and other nanoparticles, protein absorption can be dramatically reduced, resulting in less macrophage cellular uptake and therefore prolonged blood circulation times in PEGylated over non-PEGylated nanomaterials. Through systematic experiments and computer simulations, the densely packed PEG polymers are found to play the most important role in this process, which is highly related to their conformation and free energy change. Such insights may provide guidance in the design of efficient drug carriers for clinical applications.