Toxicological effects of Ag2O and Ag2CO3 doped TiO2 nanoparticles and pure TiO2 particles on zebrafish (Danio rerio)

Abstract

In this study, the toxic effects of silver oxide and silver carbonate doped TiO2 nanoparticles (Ag2O–TiO2 NPs and Ag2CO3–TiO2NPs), TiO2 nanoparticles (TiO2 NPs), and bulk TiO2 on gene expression, lipid peroxidation, genotoxicity, and histological alterations in zebrafish (Danio rerio) was assessed. The physicochemical properties of the synthesized nanoparticles were evaluated by X-ray diffraction (XRD), Scanning Electron Microscope (SEM), diffuse reflectance spectroscopy (DRS), dynamic light scattering (DLS), and Zeta potential analyses.TiO2NPs after doping with Ag showed shift to higher wavelengths and decrease of band gap energy. Also, remarkable reduction in the size of Ag-doped TiO2NPs in comparison with the TiO2 NPs was observed. According to our results, acute toxicity increased in the order of bulk TiO2 < TiO2 NPs < Ag2O–TiO2NPs < Ag2CO3–TiO2NPs, respectively. Results of sub-lethal experiments after 30 days of exposure, showed higher expression of Gpx, Hsp70, Ucp-2, and Bax genes, and lower expression of Bcl-2 gene in Ag-doped TiO2NPs than pure TiO2 particles (TiO2 NPs and bulk TiO2) treatments (p < 0.05). However, the mRNA levels of SOD and CAT genes were significantly higher in pure TiO2 particles than doped TiO2NPs (p < 0.05). Moreover, levels of malondialdehyde, abnormalities of peripheral blood cells and severity of histological lesions in liver, gill, intestine and kidney tissues were more evident in Ag-dopedTiO2 NPs than pure TiO2 particles. It can be concluded that Ag doping of TiO2 NPs significantly increased their toxicity and resulted in more histological lesions, apoptosis and oxidative stress than pure TiO2 particles in adult zebrafish.