Monitoring characteristics and genotoxic effects of engineered nanoparticle-protein corona.

Engineered nanoparticles (ENPs) possess different physical and chemical properties compared to their bulk counterparts. These unique properties have found application in various products in the area of therapeutics, consumer goods, environmental remediation, optical and electronic fields. This has also increased the likelihood of their release into the environment thereby affecting human health and ecosystem. ENPs, when in contact with the biological system have various physical and chemical interactions with cellular macromolecules including proteins. These interactions lead to the formation of protein corona around the ENPs. Consequently, living systems interact with the protein-coated ENP rather than with a bare ENP. This ENP-protein interaction influences uptake, accumulation, distribution and clearance and thereby affecting the cytotoxic and genotoxic responses. Although there are few studies which discussed the fate of ENPs, there is a need for extensive research in the field of ENPs, to understand the interaction of ENPs with biological systems for their safe and productive application.

Impact of anatase titanium dioxide nanoparticles on mutagenic and genotoxic response in Chinese hamster lung fibroblast cells (V-79): The role of cellular uptake.

The unique physico-chemical properties of nano crystalline anatase titanium dioxide nanoparticles (TiO2 NPs) render them with different biological and chemical activities. Hence, it is widely used in industrial and consumer applications. Previous studies have shown the genotoxicity of TiO2 NPs. However, there is a paucity of data regarding mutagenicity of these NPs. In the present study, the cellular uptake, sub-cellular localization, cytotoxicity and short term DNA interaction of TiO2 NPs (1-100 µgmL-1) of diameter ranging from 12 to 25 nm on mammalian lung fibroblast cells (V-79) has been studied. The flow cytometric analysis and electron micrographs of V-79 monolayer showed the internalization of TiO2 NPs in the cytoplasm with the confirmation of elemental composition through SEM/EDX analysis. TEM analysis also showed TiO2 NPs induced ultra-structural changes such as swollen mitochondria and nuclear membrane disruption in V-79 cells. TiO2 NPs generated free radicals, which induced indirect mutagenic and genotoxic responses. Apart from measuring the genotoxicity by Comet assay, the mutagenic potential of TiO2 NPs in V-79 cells was evaluated by mammalian HGPRT gene forward mutation assay, showing a 2.98- fold increase in 6TGR HGPRT mutant frequency (*p < 0.05, **p < 0.01, ***p < 0.001) by culture plate method, which is an early indicator of potential carcinogenicity. Hence, TiO2 NPs should be closely monitored and there should be a judicious use and disposal of NPs.

Heteroagglomeration of zinc oxide nanoparticles with clay mineral modulates the bioavailability and toxicity of nanoparticle in Tetrahymena pyriformis.

The extensive use of zinc oxide nanoparticles (ZnO NPs) in cosmetics, sunscreens and healthcare products increases their release in the aquatic environment. The present study explored the possible interaction of ZnO NPs with montmorillonite clay minerals in aqueous conditions. An addition of ZnO NPs on clay suspension significantly (p<0.05) increases the hydrodymic size of clay particles from 1652±90nm to 2158±13nm due to heteroagglomeration. The electrokinetic measurements showed a significant (p<0.05) difference in the electrophoretic mobilities of bare (-1.80±0.03µmcm/Vs) and ZnO NPs-clay association (-1.37±0.03µmcm/Vs) that results to the electrostatic interaction between ZnO NPs and clay particles. The attenuated total reflectance Fourier transform infrared spectroscopy analysis of ZnO NPs-clay association demonstrated the binding of ZnO NPs with the Si-O-Al region on the edges of clay particles. The increase in size of ZnO NPs-clay heteroagglomerates further leads to their sedimentation at 24h. Although, the stability of ZnO NPs in the clay suspension was decreased due to heteroagglomeration, but the bioavailability and toxicity of ZnO NPs-clay heteroagglomerates in Tetrahymena pyriformis was enhanced. These observations provide an evidence on possible mechanisms available in natural environment that can facilitate nanoparticles entry into the organisms present in lower trophic levels of the food web.

Zinc oxide nanoparticle induced age dependent immunotoxicity in BALB/c mice.

Zinc oxide (ZnO) nanoparticles (NPs) have potential applications in cosmetics, food packaging and biomedicine but concerns regarding their safety need to be addressed. In the present study, the immunotoxic potential of ZnO NPs was evaluated in different ages of BALB/c mice after sub-acute exposure. The cytokine release, immunophenotyping, distribution of ZnO NPs and ultrastructural changes were assessed. A significant (p < 0.05) change in the CD4- and CD8-cells, levels of IL-6, IFN-γ and TNF-α and reactive oxygen species were observed in aged mice. In juvenile mice, increase in reactive oxygen species and IL-6 and TNF-α levels was observed with no significant changes in adult mice. A significant (p < 0.05) increase in the expression levels of mitogen activated protein kinase (MAPK) cascade proteins such as phospho-ERK1/2, phospho-JNK and phospho-p38 were also induced in aged mice. Collectively, our results indicate that the aged mice are more susceptible to ZnO NP induced immunotoxicity.

Cell cycle dependent cellular uptake of zinc oxide nanoparticles in human epidermal cells.

Metal oxide nanoparticles (NPs), including zinc oxide (ZnO) NPs have shown success for use as vehicles for drug delivery and targeting gene delivery in many diseases like cancer. Current anticancer chemotherapeutics fail to effectively differentiate between cancerous and normal cells. There is an urgent need to develop novel drug delivery system that can better target cancer cells while sparing normal cells and tissues. Particularly, ZnO NPs exhibit a high degree of cancer cell selectivity and induce cell death, oxidative stress, interference with the cell cycle progression and genotoxicity in cancerous cells. In this scenario, effective cellular uptake of NP seems to be crucial, which is shown to be affected by cell cycle progression. In the present study, the cytotoxic potential of ZnO NPs and the effect of different cell cycle phases on the uptake of ZnO NPs were examined in A431 cells. It is shown that the ZnO NPs led to cell death and reactive oxygen species generation and were able to induce cell cycle arrest in S and G2/M phase with the higher uptake in G2/M phase compared with other phases.

ZnO nanoparticles induced inflammatory response and genotoxicity in human blood cells: A mechanistic approach.

The wide application of zinc oxide nanoparticles (ZnO NPs) in cosmetics, paints, biosensors, drug delivery, food packaging and as anticancerous agents has increased the risk of human exposure to these NPs. Earlier in vitro and in vivo studies have demonstrated a cytotoxic and genotoxic potential of ZnO NPs. However, there is paucity of data regarding their immunomodulatory effects. Therefore, the present study was aimed to investigate the immunotoxic potential of ZnO NPs using human monocytic cell line (THP-1) as model to understand the underlying molecular mechanism. A significant (p < 0.01) increase in pro-inflammatory cytokines (TNF-α and IL-1ß) and reactive oxygen species (ROS) was observed with a concomitant concentration dependent (0.5, 1, 5, 10, 15 and 20 µg/mL) decrease in the glutathione (GSH) levels as compared to control. The expression levels of mitogen activated protein kinase (MAPK) cascade proteins such as p-ERK1/2, p-p38 and p-JNK were also significantly (p < 0.05, p < 0.01) induced. Also, at the concentration tested, NPs induced DNA damage as assessed by the Comet and micronucleus assays. Our data demonstrated that ZnO NPs induce oxidative and nitrosative stress in human monocytes, leading to increased inflammatory response via activation of redox sensitive NF-κB and MAPK signalling pathways.

Chromium oxide nanoparticle-induced genotoxicity and p53-dependent apoptosis in human lung alveolar cells.

Chromium oxide (Cr2 O3 ) nanoparticles (NPs) are being increasingly used as a catalyst for aromatic compound manufacture, abrading agents and as pigments (e.g., Viridian). Owing to increased applications, it is important to study the biological effects of Cr2 O3 NPs on human health. The lung is one of the main exposure routes to nanomaterials; therefore, the present study was designed to determine the genotoxic and apoptotic effect of Cr2 O3 NPs in human lung epithelial cells (A549). The study also elucidated the molecular mechanism of its toxicity. Cr2 O3 NPs led to DNA damage, which was deduced by comet assay and cytokinesis block micronucleus assay. The damage could be mediated by the increased levels of reactive oxygen species. Further, the oxygen species led to a decrease in mitochondrial membrane potential and an increase in the ratio of BAX/Bcl-2 leading to mitochondria-mediated apoptosis induced by Cr2 O3 NPs, which ultimately leads to cell death. Hence, there is a need of regulations to be imposed in NP usage. The study provided insight into the caspase-dependent mechanistic pathway of apoptosis.