Kinetics and tissue distribution of neutron-activated zinc oxide nanoparticles and zinc nitrate in mice: effects of size and particulate nature

Although zinc oxide nanoparticles (ZnONPs) have been applied in nanotechnology, their kinetics and tissue distribution in vivo are unknown. Here we compared the kinetics and tissue distribution of 10 nm 65ZnONPs, 71 nm 65ZnONPs and 65Zn(NO3)2 in mice after intravenous injection. The areas under the curves and the half-lives in the second compartment of 65Zn(NO3)2 were greater than those of 65ZnONPs; the kinetic parameters were similar for both 65ZnONPs. However, the tissue distributions for the three forms were different. ZnONPs preferentially accumulated in the liver and spleen at 24 h. At day 28, 65Zn concentration was highest in bone and the proportion of recovered 65Zn radioactivity was highest in the carcass; these had the same ranking, 10 nm 65ZnONPs > 71 nm 65ZnONPs> 65Zn(NO3)2. Although more than 80% of the 10 nm 65ZnONPs had been excreted by day 28, greater amounts of the 10 nm 65ZnONPs than the 71 nm 65ZnONPs or 65Zn(NO3)2 had accumulated in other organs (brain, lung, heart and kidneys). Zn ions seem to have a longer half-life in the plasma, but ZnONPs show greater tissue accumulation. Although the size of the ZnONPs had no obvious effect on the kinetics, nevertheless the smaller ZnONPs tended to accumulate preferentially in some organs.