Stealth coatings for nanoparticles: Polyethylene glycol alternatives

Abstract The most acknowledged approach to impart biocompatibility and in vivo “stealth” nature to nanoparticles is by providing a thick covering of polyethylene glycol (PEG) often referred to as PEGylation. It is believed that the densely packed hydrophilic PEG chains strongly reduces interparticle attractive forces as well render a strong steric repulsion to approaching biological components such as plasma proteins and antibodies. This in turn suppresses phagocytosis and subsequent clearance from bloodstream or body. However, studies over the years pointed that PEG has major short-comings such as a very long clearance time, nonbiodegradability, and induction of anti-PEG antibodies in the body on repeated use of PEGylated products. Therefore, there is a growing interest among the biomaterials community to find alternatives to PEGylation. This chapter will briefly review the literature on developing non-PEG coatings for nanoparticles employed for biological applications.