Nanoparticle opsonization: forces involved and protection by long chain polymers

The interactions between nanoparticles and opsonins have been studied thoroughly through various models in order to elucidate the basic underlying forces of such interactions. The results of these studies give an insight about the nature of interactions and help devising methods for inhibiting opsonization. Opsonization poses major hindrance in functioning of nanoparticles. A number of forces like electrostatic, hydrophobic, van der Waal forces, etc., are involved. Among the techniques used for nanoparticle protection, PEGylation has been extensively studied and used to increase circulation times of nanoparticles. Polyethylene glycol (PEG) and PEG-like and other hydrophilic polymers with long chains have flexible nature that helps reduce opsonin adsorption on nanoparticles and hence make them stealth and unrecognized by elimination mechanisms of our body. It is suggested that polymer chain length is significant in reducing interactions between nanoparticles and opsonins. This review gives an outlook of driving forces of particulate adsorption and various mechanisms of how polymer chain length affects protein-particulate interactions. Graphic abstract