AbstractWe have prepared liposomes of dioleoylphosphatidylethanolamine (DOPE) which have been stabilized by addition of 9-12 mol% N-biotinyl- phosphatidylethanolamine. Liposomes composed of DOPE/N-biotinyl-PE are quite stable and non-leaky although they exhibit strong temperature-dependent leakage following incorporation of palmitylated murine monoclonal antibodies as a targeting ligand. Addition of magnetic chromium dioxide particles coated with anti-mouse antibody to these immunoliposomes lead to their aggregation and the release of entrapped calcein. The lytic event was biphasic with an initial rapid release of 20% dye within 5 min. followed by a slower rate which reached nearly 40% release after 80 min. The rapid release phase was dependent upon the concentration of the liposomes and that of the multivalent particles. Lysis was immunospecific since no release was observed upon addition of nonspecific immunomagnetic particles to the immunoliposomes or if no antibody was incorporated into the liposome. ...