In vivo distribution of vesicles loaded with radiopharmaceuticals: a study of different routes of administration.

The in vivo distribution of vesicles containing radiopharmaceuticals in their cavities has been studied using three routes of administration: intravenous, subcutaneous, and intraperitoneal. The in vivo distribution in mice was determined by dissection of the animals and calculation of radioactivity in the organs. In rats the in vivo distribution was assessed by scintigraphy using a scintillation camera-digital computer unit. After intravenous injection of vesicles, radioactivity is concentrated to some extent in the liver and spleen but the pattern of distribution is different from that of the corresponding free radiopharmaceutical or radiocolloid made of the corresponding radionuclide. The permeability of the vesicular membrane to contained radiopharmaceutical has been shown to vary according to the chemical composition of the vesicles. Vesicles can be used to introduce materials in vivo and the potential exists for their specific targeting by coupling other molecules to their surfaces.