Acute toxicological effects of copper nanoparticles in vivo.

Nanoparticles (NPs) can potentially cause adverse effects on organ, tissue, cellular, subcellular, and protein levels due to their unusual physicochemical properties (e.g., small size, high surface area to volume ratio, chemical composition, crystallinity, electronic properties, surface structure reactivity and functional groups, inorganic or organic coatings, solubility, shape, and aggregation behavior). Metal NPs, in particular, have received increasing interest due to their widespread medical, consumer, industrial, and military applications. However, as particle size decreases, some metal-based NPs are showing increased toxicity, even if the same material is relatively inert in its bulk form (e.g., Ag, Au, and Cu). NPs also interact with proteins and enzymes within mammalian cells and they can interfere with the antioxidant defense mechanism leading to reactive oxygen species generation, the initiation of an inflammatory response and perturbation and destruction of the mitochondria causing apoptosis or necrosis. As a result, there are many challenges to overcome before we can determine if the benefits outweigh the risks associated with NPs. WIREs Nanomed Nanobiotechnol 2010 2 544–568

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Metal-based nanoparticles and their toxicity assessment.

Because of their insolubility in water, nanoparticles have a limitation concerning toxicity experiments. The present study demonstrated a plant agar test for homogeneous exposure of nanoparticles to plant species. The effect of Cu nanoparticles on the growth of a plant seedling was studied, and bioaccumulation of nanoparticles was investigated. All tests were conducted in plant agar media to prevent precipitation of water-insoluble nanoparticles in test units. The plant species were Phaseolus radiatus (mung bean) and Triticum aestivum (wheat). Growth inhibition of a seedling exposed to different concentrations of Cu nanoparticles was examined. Copper nanoparticles were toxic to both plants and also were bioavailable. The 2-d median effective concentrations for P. radiatus and T. aestivum exposed to Cu nanoparticles were 335 (95% confidence level, 251-447) and 570 (450-722) mg/L, respectively. Phaseolus radiatus was more sensitive than T. aestivum to Cu nanoparticles. A cupric ion released from Cu nanoparticles had negligible effects in the concentration ranges of the present study, and the apparent toxicity clearly resulted from Cu nanoparticles. Bioaccumulation increased with increasing concentration of Cu nanoparticles, and agglomeration of particles was observed in the cells using transmission-electron microscopy-energy-dispersive spectroscopy. The present study demonstrated that the plant agar test was a good protocol for testing the phytotoxicity of nanoparticles, which are hardly water soluble.

Toxicity and bioavailability of copper nanoparticles to the terrestrial plants mung bean (Phaseolus radiatus) and wheat (Triticum aestivum): plant agar test for water-insoluble nanoparticles.

Roles of nanoparticles in oil lubrication

Effects of Minimum Quantity Lubrication (MQL) in machining processes using conventional and nanofluid based cutting fluids: A comprehensive review

The mending effect and mechanism of metal nano-particles in an area undergoing wear are quite important for both the fundamental theory of nano-tribology and the development of lubricant additives. This paper presents research on the mending effect of copper nano-particles added to lubricant oil. Pin-on-disk experiments and Scanning Electron Microscopy (SEM) observations show that copper nano-particles do display an excellent mending effect. The observation by Scanning Tunnelling Microscopy (STM) reveals that the mending effect results from the deposition of copper nano-particles onto the wear scar. It has also been disclosed by heating simulation that, due to nano-scale effects, which bring about decrease in the diffusion temperature of copper nano-particles, the heat generated by friction leads to the diffusion of copper nano-particles and their subsequent deposition, which finally results in the so-called mending effect.

Y. Guo

Papers

Investigation of the mending effect and mechanism of copper nano-particles on a tribologically stressed surface