Effects of humic acid and ionic strength on TiO2 nanoparticles sublethal toxicity to zebrafish

Abstract

The stability and bioavailability of titanium dioxide nanoparticles (TiO 2 NPs) suspension could be modified by the physicochemical properties of solution. In the present study, the effect of humic acid (HA) and ionic strength (by adding NaCl) on aggregation and sedimentation of TiO 2 NPs suspension were investigated. Accordingly, the sublethal toxicity of TiO 2 NPs suspensions with different HA and NaCl concentrations toward zebrafish (Danio rerio) was evaluated by monitoring the changes of superoxide dismutase, catalase, malonaldehyde and glutathione in gill, liver and intestine. The results showed that the aggregations formation and hydrodynamic diameter of TiO 2 NPs in suspensions are not essential characteristics to decide toxicity. The varied oxidative stress responses detected in gill, liver and intestine derived from different toxicity mechanisms of TiO 2 NPs. Nevertheless, the oxidative stress could be suppressed by the adding of HA and/or the increase of ionic strength, which can decrease the bioavailability of TiO 2 NPs in water. The study suggests that the environmental factors, such as HA and ionic strength, are important for the fate (aggregation and sedimentation) and toxicity of nanomaterials in aquatic environment.

Toxicity assessment of silica nanoparticles on Allium cepa

“…This can be confirmed by the DLS results, which shows that the HS30 and SM30 dispersions present a very similar size (19.10 nm and 17.10 nm, respectively), therefore reinforcing the toxicity results. Fang et al (2015) studied different primary sizes of TiO 2 NP and found a positive correlation between size and surface area or surface energy. Therefore, particles with large surface area or high surface energy usually have a more unstable thermodynamic system, and therefore tend to form aggregates.…”

A comparison of fate and toxicity of selenite, biogenically, and chemically synthesized selenium nanoparticles to zebrafish (Danio rerio) embryogenesis

“…Recently, Fang et al (2015) reported that aggregation and hydrodynamic diameter of TiO 2 nanoparticles in suspensions are not the deciding factors for the toxicity of TiO 2 nanoparticles on zebrafish (Danio rerio), rather it was the humic acid which decreases the bioavailability along with suppression of oxidative stress. However, studies on the effect of organic matter or EPS as surface coating on nano-Se are limited and more studies are required to link the surface coating of nano-Se with their properties, including their stability and dissolution in order to fully understand their environmental transformation, transport, and fate.…”

Microbial Synthesis of Chalcogenide Nanoparticles

“…Recently, Fang et al (2015) also reported that aggregation and hydrodynamic diameter of TiO2 nanoparticles in suspensions are not the deciding factors for the toxicity of TiO2 nanoparticles on zebrafish (Danio rerio), rather it was the humic acid which decreases the bioavailability along with suppression of oxidative stress. Liu and Hurt (2010) also showed that adsorption of NOM inhibited the ionic silver release from nano-Ag, while showed that microbially-derived extracellular proteins changes the transport properties of biogenic ZnS nanoparticles by retarding their dispersal.…”