Comparative Toxicity of TiO and Sn-Doped TiO Nanoparticles in Zebrafish After Acute and Chronic Exposure.

This study was conducted to assess the toxicological potential of synthesized pure and Sn-doped TiO NPs (Sn-TiO NPs) in zebrafish after acute and chronic exposure. The pure TiO NPs, 4%, and 8% Sn-TiO NPs were synthesized and characterized using X-ray diffraction, Scanning Electron Microscope, diffuse reflectance spectra, dynamic light scattering, and zeta potential analyses. The pure TiO NPs, 4%, and 8% Sn-TiO NPs were spherical with average sizes of about 40, 28, and 21 nm, respectively, indicating significant size reduction of TiO NPs following Sn doping. According to our results, the LC increased in the order of 8% Sn-TiO NPs (45 mg L) < 4% Sn-TiO NPs (80.14 mg L) < pure TiO NPs (105.47 mg L), respectively. Exposure of fish to Sn-TiO NPs after 30 days resulted in more severe histopathological alterations in gills, liver, intestine, and kidneys than pure TiO NPs. Furthermore, Sn-doping significantly elevated malondialdehyde levels and micronuclei frequency, indicating increased oxidative stress and genotoxicity. Expression analysis revealed altered expression of various genes, including upregulation of pro-apoptotic Bax gene and downregulation of anti-apoptotic Bcl-2 gene, suggesting potential induction of apoptosis in response to Sn-doped NPs. Additionally, antioxidant genes (Gpx, Sod, Cat, and Ucp-2) and stress response gene (Hsp70) showed altered expression, suggesting complex cellular responses to mitigate the toxic effects. Overall, this study highlights the concerning impact of Sn-doping on the toxicity of TiO NPs in zebrafish and emphasizes the need for further research to elucidate the exact mechanisms underlying this enhanced toxicity.