Development of Cell-Specific Liposome and Its Application in Biotechnology

Egg phosphatidylcholine liposomes were coated with naturally occurring polysaccharides bearing palmitoyl or cholesteryl group as the hydrophobic anchor. Coating the surface of liposome with these, polysaccharides makes liposome mechanically stable and cell specific, An increase in the stability of the liposomes so obtained ascertained by the depression of leakage of CF from the liposomal interior and protection of enzymatic destruction of the liposome. Cell specificity of the liposomes was monitored by the specific lectin-induced aggregation, the cell uptake, and the tissue distribution in animals. Liposomes coated with amylopectin or mannan derivative showed increased endocytosis with macrophages and effective uptake by the lungs after intravenous injection into guinea pigs. Encapsulation of antimicrobial agents (amphotericin B, ampicillin, minocycline, and sisomycin) and immunomodu-lator (polyanionic polymers) into these polysaccharide-coated liposomes resulted in both enhanced pharmaceutical activities, such as anti-fungal activity and macrophage activation, and decreased side effect. In order to increase the targetability of liposome to tumor cells, monoclonal antibody fragment (anti-sialosylated Lewis^x, IgM) was conjugated with pullulan derivatives bearing maleimido group as the coupling unit. Such the immunoliposome so obtained showed significantly the specific binding to PC-9 lung squamous cell carcinoma in vitro, and selectively high accumulation in vivo at the subcutaneously implanted tumor. Encapsulation of adria-mycin into the immunoliposome resulted in more significant inhibition in the tumor growth compared with simple pullulan-coated liposome without the specific sensory device.