Differential oxidative stress of octahedral and cubic Cu2O micro/nanocrystals to Daphnia magna

Comparative evaluation of intestinal nitric oxide in embryonic zebrafish exposed to metal oxide nanoparticles

Nanoparticle (NP) exposure may induce oxidative stress through generation of reactive oxygen and nitrogen species, which can lead to cellular and tissue damage. The digestive system is one of the initial organs affected by NP exposure. Here, it is demonstrated that exposure to metal oxide NPs induces differential changes in zebrafish intestinal NO concentrations. Intestinal NO concentrations are quantified electrochemically with a carbon fiber microelectrode inserted in the intestine of live embryos. Specificity of the electrochemical signals is demonstrated by NO-specific pharmacological manipulations and the results are correlated with the 4,5-diaminofluorescein-diacetate (DAF-FM-DA). NPs are demonstrated to either induce or reduce physiological NO levels depending on their redox reactivity, type and dose. NO level is altered following exposure of zebrafish embryos to CuO and CeO2 NPs at various stages and concentrations. CuO NPs increase NO concentration, suggesting an intestinal oxidative damage. In contrast, low CeO2 NP concentration exposure significantly reduces NO levels, suggesting NO scavenging activity. However, high concentration exposure results in increased NO. Alterations in NO concentration suggest changes in intestinal physiology and oxidative stress, which will ultimately correspond to NPs toxicity. This work also demonstrates the use of electrochemistry to monitor in vivo changes of NO within zebrafish organs.

Fate and toxicity of CuO nanospheres and nanorods used in Al/CuO nanothermites before and after combustion

Although nanotechnology advancements should be fostered, the environmental health and safety (EHS) of nanoparticles used in technologies must be quantified simultaneously. However, most EHS studies assess the potential implications of the free nanoparticles which may not be directly applicable to the EHS of particles incorporated into in-use technologies. This investigation assessed the aquatic toxicological implications of copper oxide (CuO) nanospheres relative to CuO nanorods used in nanoenergetic applications to improve combustion. Particles were tested in both the as-received form and following combustion of a CuO/aluminum nanothermite. Results indicated nanospheres were more stable in water and slowly released ions, while higher surface area nanorods initially released more ions and were more toxic but generally less stable. After combustion, particles sintered into larger, micrometer-scale aggregates, which may lower toxicity potential to pelagic organisms due to deposition from water to sediment and reduced bioavailability after complexation with sediment organic matter. Whereas the larger nanothermite residues settled rapidly, implying lower persistence in water, their potential to release dissolved Cu was higher which led to greater toxicity to Ceriodaphnia dubia relative to parent CuO material (nanosphere or rod). This study illustrates the importance of considering the fate and toxicology of nanoparticles in context with their relevant in-use applications.

Chemical mechanisms of the toxicological properties of nanomaterials: generation of intracellular reactive oxygen species

As more and more nanomaterials with novel physicochemical properties or new functions are created and used in different research fields and industrial sectors, the scientific and public concerns about their toxic effects on human health and the environment are also growing quickly. In the past decade, the study of the toxicological properties of nanomaterials/nanoparticles has formed a new research field: nanotoxicology. However, most of the data published relate to toxicological phenomena and there is less understanding of the underlying mechanism for nanomaterial-induced toxicity. Nanomaterial-induced reactive oxygen species (ROS) play a key role in cellular and tissue toxicity. Herein, we classify the pathways for intracellular ROS production by nanomaterials into 1) the direct generation of ROS through nanomaterial-catalyzed free-radical reactions in cells, and 2) the indirect generation of ROS through disturbing the inherent biochemical equilibria in cells. We also discuss the chemical mechanisms associated with above pathways of intracellular ROS generation, from the viewpoint of the high reactivity of atoms on the nanosurface. We hope to aid in the understanding of the chemical origin of nanotoxicity to provide new insights for chemical and material scientists for the rational design and creation of safer and greener nanomaterials.