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Iron oxide nanoparticles (IONPs) are known to induce cytotoxicity in various cancer cell lines through the generation of reactive oxygen species (ROS). However, the studies on its potential to induce toxicity in normal cell lines and in vivo system are limited and ambiguity still exists. Additionally, small molecules are known to interact with the DNA and cause damage to the DNA. The present study is designed to evaluate the potential interaction of IONPs with DNA along with their other toxicological effects and subsequent attenuation by thymoquinone both in vitro (primary lymphocytes) and in vivo (Wistar rats). IONPs were characterized by TEM, SEM-EDS, and XRD. The results from DNA interaction studies showed that IONPs formed a complex with DNA and also got intercalated between the base pairs of the DNA. The decrease in percent cell viability of rat’s lymphocytes was observed along with an increase in ROS generation in a dose-dependent manner (50, 100, 200, 400 and 800 μg/ml of IONPs). The genetic damage in in vivo might be due to the generation of ROS as depletion in anti-enzymatic activity was observed along with an increase in lipid peroxidation in a dose–dependent manner (25, 50, 100 mg/kg of IONPs). Interestingly, supplementation of thymoquinone in combination with IONPs has significantly ( P < 0.05) attenuated the genetic and oxidative damage in a dose-dependent manner both in vitro and in vivo . It can be concluded that thymoquinone has the potential to attenuate the oxidative stress and genetic toxicity in vitro and in vivo .

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Titanium dioxide nanoparticles (TiO2 NPs, size <100 nm) find applications in a wide range of products including food and cosmetics. Studies have found that exposure to TiO2 NPs can cause inflammation, cytotoxicity, genotoxicity and cell apoptosis. In this article, we have reviewed the recent literature on the potential of TiO2 NPs to cause genotoxicity and summarized the results of two standard genotoxicity assays, the comet and micronucleus (MN) assays. Analysis of these peer-reviewed publications shows that the comet assay is the most common genotoxicity test, followed by MN, Ames, and chromosome aberration tests. These assays have reported positive as well as negative results, although there is inconsistency in some results that need to be confirmed further by well-designed experiments. We also discuss the possible mechanisms of TiO2 NP genotoxicity and point out areas that warrant further research.

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