ABSTRACT
Use of liposomes as an effective drug-delivery system requires the development of vesicles with physical characteristics appropriate to the drug itself and the therapeutic function it is to perform. The liposomal carrier would prove most effective if it were able both to remain for long periods of time in the circulation and to retain entrapped drugs quantitatively so that interaction with target cells within vascular system may occur effectively. Stability of small unilamellar liposomes of different lipid compositions in the presence of plasma, serum or whole blood is usually compared with that in buffer under standardized physiological conditions of temperature and pH by measuring changes in carboxyfluorescein (CF) latency. In experiments in which liposomes with entrapped CF are to be injected, CF latency immediately prior to injection with all samples brought to room temperature should be measured. While estimation of liposomal clearance rates can be carried out with stable vesicles, their distribution in tissues is much more difficult to measure.
