Agent Targeting by Means of the Chemically or Physically Directed, Fusogenic Liposomes

Abstract

increasing the temperature and/or lowering the pH-value in the investigated system are most useful for this purpose the role of membrane defects, such as may arise during the liposo-me manufacturing process or in the vicinity of lipid phase transitions also being of extreme importance. Thermolabile fusogenic liposomes prepared from the stoichiometric 1/2 mixture of diacylphoshatidylcholines with appropriate fatty acids implement these re uirements. $heir temperature dependence permitting physical targeting an8 their pHdependence being suitable for the ‘chemical targeting’ to the acidic surrounding. Dipalmitoylphosphatidylcholine/elaidic acid mixture is, perhaps, the best such combination for the use in vivo. The efficacy of fusion between the corTesponding lipid vesicles and cells in vitro as well as the delivery of radioactive labels into the heated tumours (but not in the normal muscle tissue with the inpenetrable micro-vasculature) provide compelling evidence for this.