Description
Liposomes can be surface-modified with a variety of molecules that carry out number of functions such as promoting the targeting of the vesicles to specific tissues, cell types and/or modulate, e.g., by PEGylation, their biodistribution and pharmacokinetic properties. Targeting, which represents a major issue to increase the specificity and efficiency of bioactive molecules (drugs, genes, etc.) delivery, involves, in most cases, the use of ligands that are recognized by receptors (over)expressed at the surface of target cells. These ligands are either relatively small molecules, such as folic acid, peptides or carbohydrate clusters which trigger receptor-mediated endocytosis, or proteins such as monoclonal antibodies and their fragments, that are directed against specific antigens.