Comparison of the biodistribution in mice of (111)indium oxine encapsulated into poly(lactic-co-glycolic)-D,L-85/15 and poly(epsilon caprolactone) nanocapsules

Poly(lactic-co-glycolic)-D,L-85/15 (PLAGA) nanocapsules and poly(epsilon ca prolactone) (PCL) nanocapsules were labeled with a relatively long half-lif e compound that is usually used in humans; that is, In-111-labelled oxine ( In-111 oxine). This labeling technique led to a high In-111 oxine entrapmen t efficiency and good stability during dialysis against phosphate buffer an d phosphate buffered albumin solution. Because of these characteristics, th e nanocapsules biodistribution was followed up after intravenous administra tion for up to 96 h by determining the gamma activity in the tissues after sampling. The administration of the PCL-encapsulated In-111 oxine led to a decrease in the blood radioactivity and an increase in the liver radioactiv ity compared with the solution. This effect was even more pronounced with t he PLAGA nanocapsules. Finally, the activity level in other tissues, such a s the kidneys, the lungs, and the spleen, appeared to be rather low and onl y slightly affected by the encapsulation into one or the other polymer.