Biodistribution of dual radiolabeled lipidic nanocapsules in the rat using scintigraphy and gamma counting

The aim of the present work was to study the biodistribution of a radiolabeled lipidic nanocapsule formulation after intravenous administration in rat by scintigraphy and gamma counting. This formulation is expected to be used as anticancer agent delivery devices and as transfection complexes. For this purpose, 99mTc-oxine was incorporated in the lipidic core, while 125I labeled tensioactive shell of the nanocapsule. First, in vitro stability of radiolabeled nanocapsules was evaluated by dialysis against distilled water and size measurements. Second, the nanocapsule biodistribution was followed after intravenous administration for 3 h by dynamic scintigraphic acquisition and up to 24 h by determining the gamma activity in blood and tissues. Radiolabeling was efficient and stable in vitro. After intravenous injection blood radioactivity decreased with an early half disappearance time of about 45 min for both radioisotopes. Liver and intestine radioactivities raised up to 24 h. The relatively long remanence in blood of the tracers which is probably due to the presence of PEG at the nanocarrier surface seems promising for the use of these solvent free lipidic nanocapsules as carrier of lipophilic drugs.