The effect of nano-scale Zn-doped TiO2 and pure TiO2 particles on Hydra magnipapillata

Abstract

Zn-doped nano-scale TiO 2 is a useful material in the production of both hydrogen energy and LEDs. However, scientists have raised concerns regarding the toxicity of nano-scale materials. In this study, we investigated the biological toxicity of nano-scale Zn (0.1, 0.5, and 1 mol%)-doped TiO 2 and pure TiO 2 nanoparticles using the freshwater cnidarian Hydra magnipapillata as our model organism. Zn-doped TiO 2 nanoparticles were prepared using a conventional hydrothermal method for the insertion of zinc into the TiO 2 framework. The character of Zn-doped TiO 2 (0.1%, 0.5%, 1% Zn) and pure TiO 2 was 7-8 nm with a positive surface charge. The size was smaller than that used in previous research on the toxicity of nano-scale materials. Although, in this study, we found no significant biological toxicity in Hydra magnipapillata, there was some damage under Zn-doped TiO 2 and pure TiO 2 UV-A photocatalysis conditions. We assessed that the damage was not linked to the nanoparticles, but rather due to the photocatalytic reaction. Moreover, Zn-doped TiO 2 and pure TiO 2 nanoparticles were not shown to cause cytotoxic effects, like apoptosis and necrosis that are the major markers of toxicity in organisms exposed to nanomaterials. There was no difference in necrosis or apoptosis, as viewed with a confocal laser microscope, between the Zn-doped TiO 2 nanoparticleexposed group and control groups. This study suggests that particles under 10 nm in size do not exhibit biological toxicity and that the small particle size of Zndoped TiO 2 and TiO 2 nanoparticles decreases photocatalytic effect.TiO 2 photocatalysis is useful in the degradation of environmental chemicals, such as, VOCs 1 and bisphenol A 2-5 . Nano-scale TiO 2 particles have the ability to increase the effect of photocatalysis. Moreover, noble metals (Cu, Ni, Pd, Pt, Au) doped with TiO 2 , can be used to activate the photocatalysts with longer-wavelength UV light 6-8 . Metal-doped TiO 2 is also useful for solar energy panels and in the production of hydrogen energy and LEDs.Nano-scale TiO 2 and ZnO particles also have wide use in UV sunscreen products, but scientists have raised concerns regarding the toxicity of nano-scale materials. Although nano-scale TiO 2 and ZnO do not penetrate human skin 9-11 , both enter the aquatic environment via wastewater effluent (Wiench et al., 2009). In previous reports, we investigated the toxic impacts of nano-scale particles on aquatic ecosystems using nano-silver or Cu-doped TiO 2 nanoparticles 12-15 . We found that rat and human alveolar macrophages had impaired function due to aggregation of ultrafine carbon particles, which may be linked to an increased risk of infection and inflammation of lung cells 16,17 .However, the relationship between the size effects of nano-scale materials and the biological toxicity is an inadequate explanation for the observed toxicity. Thus, research on the surface properties of nano-scale materials is urgently needed, yet little is known about its effects on the cell.The varied reactions of nano-...

Hydra, a model system for environmental studies

“…The uptake of positively charged nanoparticles involved annexin proteins in the cell membranes which are involved in pro-apoptotic mechanisms of cell death. In another study, the toxicity of uncapped titanium dioxide and zinc-capped titanium dioxide was also examined in the Hydra to determine the resulting effects of capping in the Hydra (Yeo and Kang, 2010). Although there was no marked overall toxicity of these nanoparticles as determined by the absence of tissue necrosis or apoptotic cells, some damage was found with zinc capped TiO 2 and uncapped TiO 2 under UV-A photo conditions.…”

Effect of 10 different TiO2 and ZrO2 (nano)materials on the soil invertebrate Enchytraeus crypticus

“…The effect of TiO 2 photocatalytic activity has been largely explored for the removal of pollutants from water and soil . Despite the knowledge on the photoactivation mechanism , which leads to the formation of reactive oxygen species (ROS), studies focusing on the effects of UV radiation on TiO 2 toxicity to living organisms have only recently been carried out on aquatic organisms, showing that UV enhances the toxicity of TiO 2 NPs .…”

Effects of Pollution on Freshwater Organisms

“…No toxicity was observed when Hydra magnipapillata were exposed to nanoparticles of TiO2 and Zn-doped TiO2 (Yeo and Kang, 2010 Nanosilver and quantum dots altered the expression of transcripts linked to T-3 and stress-mediated pathways.…”