Polysaccharide-coated liposomes have been developed to improve the stability of conventional liposomes against biochemical and physicochemical stimuli. Pullulan (MW 5 × 104) was used as the polysaccharide. the mouse IgM monoclonal antibody (CSLEX 1) recognizes a sialosylated Lex, which is a tumor-specific antigen in athymic mice. the IgM antibody was reduced with cysteine to obtain the subunit (IgMs) that remained biologically active. the IgMs was accumulated in an antigen-positive tumor in vivo. Subsequently, it was conjugated with the pullulan-coated liposome to form an immunoliposome. Tissue distribution studies demonstrated that immunoliposomes were more efficiently targeted to an implanted tumor than to the polysaccharide-coated liposomes. This is accompanied by a drastic decrease in liver uptake of the immunoliposomes. Furthermore, adriamycin-encapsulated immunoliposomes in-hibited the growth of the implanted tumor more effectively than did the simple pulluian-coated liposomes.
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