An in vivo and ex-vivo study of biodistribution and accumulation of Quantum Dots

In the present study we investigate the impact of nanoparticles in an in vivo and ex-vivo system. At this aim Balb-C female mice are treated with Quantum Dots (QDs) (1:5 dilutions of commercial solution 2 µM /0.01ml/g mouse, i.v) and sacrificed 3h, 24h and one week after injection (n=3 treated and n=3 control mice for every time point). Quantitative and qualitative bio-distribution of such nanoparticles is achieved by optical imaging and electron microscopy analysis. Optical data, acquired by a VivoVision Systems, IVIS®200 Series, Xenogen, show accumulation of QDs in anatomical region corresponding to brain, liver, spleen and lung. These results are supported by electron microscopy studies. After surgically extraction, the organs are fixed in 4% PF and embedded in LRW resin. Sections from every sample are collected on carbon coated nickel grid and observed with Philips Morgagni electron microscope equipped with a 40-50 µm objective aperture and operating at 80 kV. QDs takeover is not identify with membrane receptor system. Accumulation of such nanoparticles is detected in several cell types of those target organs. In particular 3h after injection QDs are localized in mitochondria, on the smooth endoplasmatic reticulum and in the lysosomes. Nuclei as well are labelled on dense chromatin and in the interchromatin space. Statistical analysis evidence a significant percentage of cells affected by QDs accumulation. The kinetics of cadmium, selenium and tellurium, present in the QDs and detected in different organs after their mineralization, was studied by Inductively Coupled Plasma/Mass Spectrometer (ICP-MS) analysis. The results validate the QDs storage in tissues.