Study of drug delivery into the cytoplasma with targeted liposomes.

Several parameters have been established as important for the efficient delivery of liposomes-associated molecules. A non-exhaustive list includes parameters, such as size of liposomes, lipid composition, nature of the encapsulated molecule, the nature of the target molecule and the cell type expressing it. Of these, we studied size of liposomes and target molecules on human T lymphocytes. Liposomes, composed of dipalmitoylphosphatidylcholin, cholesterol and the modified phosphatidylethanolamine used to couple Protein A, were used as a model system to demonstrate drug transfer into specific lymphoid cells. Protein A, which selectively recognizes mouse IgG2 antibodies, was coupled to liposomes to target them specifically to defined cells types coated with IgG2 antibody. Methotrexate(MTX)-containing liposomes of different sizes (0.05, 0.1, or 0.2 μm), targeted to the major histocompatibility complex(MHC)-encoded class I molecules, were evaluated by their efficiency. It was clearly demonstrated that large liposomes are internalized by human lymphoid cells less well than smaller liposomes. And we have examined two T lymphocyte cell surface molecules, CD4 and CD7, as targets for specific drug delivery of drugs from targeted liposomes. CD? was shown to he a good target for drug delivery. But CD4 targeted liposomes, in contrast, was ineffective.