Transformation in band energetics of CuO nanoparticles as a function of solubility and its impact on cellular response

Nanoparticles under a reactive microenvironment, have the propensity to undergo morphological and compositional changes, which can translate into band edge widening. Although cell membrane depolarization has been linked with the electronic band structure of nanomaterials in their native state, the change in band structure as a consequence of a soluble nanoparticle system is less studied. Therefore we studied the consequence of dissolution of CuO nanoparticles on the band structure and flat band potentials and correlated it with its ability to induce a intracellular oxidative stress. The temporal variation in bandgap, fermi energy level and valence band maxima were evaluated on the remnant CuO nanoparticles post dissolution. CuO nanoparticles showed a very high dissolution in simulated body fluid (51%) and cell culture media (75%). This dissolution resulted in an in situ physico-chemical transformation of CuO nanoparticles. A temporal increase in the bandgap energy as a result of media interaction was up to 107%. Temporal variation in the flat band potentials with the generation of intracellular ROS, cell viability, late and early apoptosis in addition to necrosis on RAW 264.7 cells was established due to biological redox potential overlap. The mRNA expression for TNF-α, IL-6, IL-1β and IL-10 in response to the particle treatment was also evalulated for 6 hours. Through this study, we establish that the toxicological potential of CuO nanoparticles is a temporal function of band energies (its overlap with the intracellular redox potential) followed by release of ionic species in the cytotoxic regime.

Defect-induced electronic states amplify the cellular toxicity of ZnO nanoparticles

Zinc oxide nanoparticles (ZnO NPs) are used in numerous applications, including sunscreens, cosmetics, textiles, and electrical devices. Increased consumer and occupational exposure to ZnO NPs potentially poses a risk for toxicity. While many studies have examined the toxicity of ZnO NPs, little is known regarding the toxicological impact of inherent defects arising from batch-to-batch variations. It was hypothesized that the presence of varying chemical defects in ZnO NPs will contribute to cellular toxicity in rat aortic endothelial cells (RAECs). Pristine and defected ZnO NPs (oxidized, reduced, and annealed) were prepared and assessed three major cellular outcomes; cytotoxicity/apoptosis, reactive oxygen species production and oxidative stress, and endoplasmic reticulum (ER) stress. ZnO NPs chemical defects were confirmed by X-ray photoelectron spectroscopy and photoluminescence. Increased toxicity was observed in defected ZnO NPs compared to the pristine NPs as measured by cell viability, ER stress, and glutathione redox potential. It was determined that ZnO NPs induced ER stress through the PERK pathway. Taken together, these results demonstrate a previously unrecognized contribution of chemical defects to the toxicity of ZnO NPs, which should be considered in the risk assessment of engineered nanomaterials.

Montmorillonite clay and humic acid modulate the behavior of copper oxide nanoparticles in aqueous environment and induces developmental defects in zebrafish embryo

Copper oxide nanoparticles (CuO NPs) is one of the most commonly used metal oxide nanoparticles for commercial and industrial products. An increase in the manufacturing and use of the CuO NPs based products has increased the likelihood of their release into the aquatic environment. This has attracted major attention among researchers to explore their impact in human as well as environmental systems. CuO NPs, once released into the environment interact with the biotic and abiotic constituents of the ecosystem. Hence the objective of the study was to provide a holistic understanding of the effect of abiotic factors on the stability and aggregation of CuO NPs and its correlation with their effect on the development of zebrafish embryo. It has been observed that the bioavailability of CuO NPs decrease in presence of humic acid (HA) and heteroagglomeration of CuO NPs occurs with clay minerals. CuO NPs, CuO NPs + HA and CuO NPs + Clay significantly altered the expression of genes involved in development of dorsoventral axis and neural network of zebrafish embryos. However, the presence of HA with clay showed protective effect on zebrafish embryo development. These findings provide new insights into the interaction of NPs with abiotic factors and combined effects of such complexes on developing zebrafish embryos genetic markers.