Polysaccharide-Coated Immunoliposomes Bearing Anti-CEA Fab' Fragment and Their Internalization by CEA-Producing Tumor Cells

Immunoliposomes, bearing Fab' fragments of anti-carcinoembryonic antigen (anti-CEA) monoclonal antibody, have been prepared according to a new method developed in our laboratory. First, egg phosphatidylcholine liposomes were coated with pullulan derivatives. Then, SH-bearing Fab' fragments of anti-CEA were conjugated to the pullulan derivatives attached to the liposomal surface. These immunoliposomes showed specific binding to CEA-producing cells, BM314, which was approximately 20-fold greater than to CEA-non- producing cells, RPMI #4788. In addition, these immunoliposomes were endo cytosed by colon cancer cells, which was confirmed by fluorescence microscopy using liposomes labelled by a hydrophobic fluorescent probe, terbium trisace tylacetonate.