Vesicle targeting: timed release and specificity for leukocytes in mice by subcutaneous injection.

When unilamellar vesicles were administered subcutaneously in mice, the half-time for the destruction of the vesicles varied from 12 to 600 hours, depending on their composition. The vesicles tested consisted of distearoyl phosphatidylcholine, cholesterol, and certain sugar and amino-sugar derivatives of cholesterol. Vesicle with amino-sugar derivatives showed the greatest longevity and became localized with high specificity in aggregates of polymorphonuclear leukocytes. A substantial delay between the time that the vesicles broke open and the time that labels contained in the vesicles were excreted suggests that the vesicles undergo endocytosis before destruction.