The use of radioactive zinc oxide nanoparticles in determination of their tissue concentrations following intravenous administration in mice.

The increasing uses of zinc oxide nanoparticles (ZnONPs) in coatings, paints, personal care products and many other products increase the possibility of the body's exposure to ZnONPs. Accurate and quantitative profiling on the tissue distribution and body clearance of ZnONPs, which is an important factor to clarify the acute and chronic safety concerns of ZnONPs, is interfered by the abundance of the body's endogenous zinc moiety. In this report, radioactive zinc oxide nanoparticles (R-ZnONPs) generated from neutron activation were employed for the in vivo bio-distribution studies using mice as the animal model. Gamma-ray emitting radioactive R-ZnONPs were produced from neutron activation. Zeta potentials of the ZnONPs before and after the neutron irradiation remained about the same, and R-ZnONPs largely remained its original nano-particulate form after neutron irradiation. After intravenous administration into ICR mice, R-ZnONPs exhibited a primary retention in lung (43.6% injected dose (ID)/g tissue wet weight) for the first hour and began to be translocated to intestinal tract for feces excretion at a later stage. This type of labeling free and radioactive nanoparticles retains the surface property and can be a convenient protocol for studying bio-distribution of nanoparticles in pristine chemical form.

The chemical fate of the Cd/Se/Te-based quantum dot 705 in the biological system: toxicity implications.

QD705 is a cadmium/selenium/tellurium (Cd/Se/Te)-based quantum dot with good potential for biomedical applications. Although the biological fate of QD705 is established, its chemical fate in the biological system is still unknown. Since the chemical nature of Cd in QD705 (either stays as bounded Cd or becomes free Cd) is closely related to the toxicity of this nanocrystal, information on its chemical fate is critically needed. In this study we investigated the chemical fate of QD705 in the kidneys of mice. We used the molar ratio of Cd and Te (increased Cd/Te ratio signifies increased Cd release from QD705) and the induction of tissue metallothionein (MT) as markers for elevated free Cd in tissues. Our study indicated that 100% of QD705 (measured as Cd) was still retained in the body 16 weeks after exposure, with significant time redistribution to the kidneys. Furthermore, there were an elevation in both the molar Cd/Te ratio and MT-1 expression in the kidneys, suggesting that free Cd was released from QD705. Thus QD705 is not as stable or biologically inert as many may have once believed. Our study demonstrated that free Cd indeed can be released from QD705 in the kidneys and increases the risk of renal toxicity.