Interactions of phospholipid- and poly(ethylene glycol)-modified surfaces with biological systems: relation to physico-chemical properties and mechanisms

This paper critically reviews reports on the interactions of phospholipids and poly(ethylene glycol) (PEG)-also called poly(ethylene oxide) (PEO)-with biological systems (model polypeptides, proteins. macrophages. etc). The review arises from the need to rationalize the widely varying Findings reported in the literature. The paper discusses the interaction of simple polypeptides with phospholipids. followed by the interaction of proteins with supported phospholipid layers and liposomes. In addition, the interactions of liposomes with more complex biological systems, in vitro and in vivo, are discussed. Since many proposed liposome formulations contain grafted PEG molecules, a discussion of the interactions of PEG molecules and PEG surface layers with proteins is also provided as well as a substantial section dealing with the mechanistic aspects of these interactions, As well as providing an introduction to the multidisciplinary and complex literature available, we hope that this review article will provide the necessary information for more rational design of systems and devices for in vivo application. In particular. the article stresses the need for much better characterization of the systems and materials used. (C) 2002 Elsevier Science B.V. All rights reserved.