キャリアーの分子設計:

血中滞留形リポソーム

抄録

Liposomes have attracted a considerable amount of interest for potential use as a drug delivery system due to their suitable characteristics. However, the predominant uptake of liposomes by the reticuloendotherial system (RES) and a resulting rapid clearance from circulation have been a major obstacle in any attempt to deliver liposomes to cells, tissue or organs other than the RES. One of the current efforts is to overcome the above kinetic barrier by manipulating the liposome characteristics. Some attempts have been made to reduce the RES uptake by surface modification with glycolipids or synthetic polymers. Especialy, incorporation of polyctyleneglycol-lipid derivatives(PEG) in liposome led to increased blood levels of liposomes and reduced uptake by the RES. In this review, various designs of PEG containing liposomes are presented, characterization of PEG-liposomes and possible mechanisms of action are discussed. It is suggested here that the primary mechanism by which PEG molecules alter the biodistribution of liposomes in vivo involeves an inhibition of the association of blood components(opsonin ?) to liposomes, resulting in a reduced rate of clearance of liposomes from the circulation. The many advantages of long-circulating liposomes, such as PEG-liposome, make them excellent candidates as drug delivery systems for sustained drug release or drug targeting application.