pH-sensitive immunoliposomes composed of dioleoylphosphatidyl-ethanolamine and oleic acid (8:2) significantly enhanced the cytotoxic effect of the entrapped drug 1-beta-D-arabinofuranosylcytosine (ara-C) to target L-929 cells, as compared to free drug, drug encapsulated in antibody-free liposomes, or in pH-insensitive immunoliposomes. These pH-sensitive immunoliposomes were ineffective against ...