| Popis: |
Studies in animal tumor models have found that the therapeutic effects of antican-cer drugs can be enhanced and prolonged, and their toxic side effects reduced, when the drugs are encapsulated in liposomes.1,2 The effectiveness of drugs in conventional liposomes is limited, however, by their rapid uptake by the cells of the mononuclear phagocytic system (MPS), reducing the amount of drug that reaches the tumor.3 By the covalent attachment of polyethylene glycol (PEG) to the lipid bi-layers of the liposomes, the uptake of liposomes by the MPS is reduced, and the circulation time is increased 4,5 Such liposomes are often referred to as sterically stabilized in analogy to stabilization of organic colloid particles, in which steric modifications of the particle surface result in reductions in particle-to-particle interactions that could lead to aggregation or fusion. In colloids, steric stabilization is accomplished by addition of surface charge or via coating of the surface with various molecules such as starch or PEG.6 In the case of liposomes in biological environments, steric stabilization not only reduces particle-to-particle interactions, but also decreases adsorption of various macromolecules onto the liposome surface, loss of liposomal components to other particles, and interactions of the liposomes with cells, all of which provide greater liposome stability compared to conventional, nonpegylated liposomes.7,8 This liposome property has been given the registered trade name “STEALTH”. |
