ABSTRACT
Nanospheres, nanocapsules, liposomes, and micelles are widely used for delivery of diagnostic agents and therapeuticals. Liposomes may serve as a good model to understand the influence of a grafted polymer on carrier properties, and many regularities found for liposomes might be successfully applied to any microparticulate drug carrier. One of the most popular and successful methods to prepare biologically stable and long-circulating liposomes for drug-delivery purposes is their coating with poly(ethylene glycol). Liposomal elimination from the blood proceeds mainly by the recognition of liposomes by phagocytic cells that is mediated by opsonins. A good example of a practical use of the particle surface modification with synthetic polymers is a design of liposome-based contrast agents for lymph node magnetic resonance imaging. In addition to liposomes, synthetic amphiphilic polymers also have been used for steric stabilization of particles with a hydrophobic surface to prolong their circulation in the blood and to alter the biodistribution.
