Polyethylene glycol stealth liposomes

Several of these problems can be solved by polyplex modification with polyethylene glycol (PEG). PEGylation has been broadly explored for surface shielding ( stealthing ) of many liposomal and nanoparticulate carriers. In the case of cationic polymers, Plank et al. [62] demonstrated that complement activation can be reduced when the polymers are PEGylated. Such a modification can be... 

Lipid moieties coupled to polyethylene glycol (PEG) have been used to increase the blood circulation time of lipoplexes (Fig. 32). The PEG-lipid conjugates such as DOPE-PEG, Chol-PEG, ceramides-PEG and their derivatives are then coformulated with the cationic lipid, helper lipid, and DNA. This results in coating the surface of the lipoplexes with PEG and preventing undesired association with plasma proteins or circulating cells (stealth liposomes). Recently, a-tocopheryl PEG-succinate (TPGS) was also used in gene delivery formulations because of its ability to confer not only a stealth property but also antioxidant and absorption enhancer properties [129]. 

Sterically stabilized liposomal doxorubicin (pegylated liposomal doxorubicin Caelyx/Doxil) is coated with polyethylene glycol (3), which results in so-called stealth liposomes. In liposomal daunorubicin the liposome consists of a lipid bilayer of distearoylphosphati-dylcholine and cholesterol in a 2 1 molar ratio (4). Both formulations have a hydrophilic outer layer, which attracts a coating of water around the liposomal shell. This increases the circulation time by making the formulation virtually invisible to the reticuloendothelial system. 

Efficient liposomal therapeutics also require long circulation times. Normal liposomes are cleared from the blood rapidly by the reticuloendothehal systan, but circulation times can be easily increased by giving the liposomes a so-called stealth character. Stealth liposomes are sterically stabilized by lipids with a long polyethylene glycol unit attached to the headgroup, usually phosphatidylethanolamine (PE). ... 

Stealth liposomes, containing therapeutic drugs and coated with polyethylene glycol, may assist evasion of immune systems and enable targets to be reached in the body. 

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