In Vitro and in Vivo Behavior of Liposomes Decorated with PEGs with Different Chemical Features.

The colloidal stability, in vitro toxicity, cell association, and in vivo pharmacokinetic behavior of liposomes decorated with monomethoxy-poly(ethylene glycol)-lipids (mPEG-lipids) with different chemical features were comparatively investigated. Structural differences of the mPEG-lipids used in the study included: (a) surface-anchoring moiety [1,2-distearoyl--glycero-3-phosphoethanolamine (DSPE), cholesterol (Chol), and cholane (Chln)]; (b) mPEG molecular weight (2 kDa mPEG and 5 kDa mPEG); and (c) mPEG shape (linear and branched PEG). In vitro results demonstrated that branched (mPEG)-DSPE confers the highest stealth properties to liposomes (∼31-fold lower cell association than naked liposomes) with respect to all PEGylating agents tested.