Size matters – The phototoxicity of TiO2 nanomaterials. (January 2016)

• Record Type: Journal Article
• Authors: Wyrwoll, Anne J.; Lautenschläger, Petra; Bach, Alexander; Hellack, Bryan; Dybowska, Agnieszka; Kuhlbusch, Thomas A.J.; Hollert, Henner; Schäffer, Andreas; Maes, Hanna M.
• Is Part Of: Environmental pollution. Volume 208:Part B(2016)
• Page Start: 859
• Page End: 867
• Publication Date: 2016-01
• Subjects: Daphnia magna -- TiO2 nanoparticles -- Solar radiation -- Reactive oxygen species -- Phototoxicity; Pollution -- Periodicals; Pollution -- Environmental aspects -- Periodicals; Environmental Pollution -- Periodicals; Pollution -- Périodiques; Pollution -- Aspect de l'environnement -- Périodiques; Pollution -- Effets physiologiques -- Périodiques; Pollution; Pollution -- Environmental aspects; Periodicals; Electronic journals; 363.73
• DOI: 10.1016/j.envpol.2015.10.035
• Languages: English
• ISSNs: 0269-7491

Abstract

Abstract: Under solar radiation several titanium dioxide nanoparticles (nano-TiO2 ) are known to be phototoxic for daphnids. We investigated the influence of primary particle size (10, 25, and 220 nm) and ionic strength (IS) of the test medium on the acute phototoxicity of anatase TiO2 particles to Daphnia magna . The intermediate sized particles (25 nm) showed the highest phototoxicity followed by the 10 nm and 220 nm sized particles (median effective concentrations (EC50): 0.53, 1.28, 3.88 mg/L). Photoactivity was specified by differentiating free OH radicals (therephthalic acid method) and on the other hand surface adsorbed, as well as free OH, electron holes, and O 2 − (electron paramagnetic resonance spectroscopy, EPR). We show that the formation of free OH radicals increased with a decrease in primary particle size (terephthalic acid method), whereas the total measured ROS content was highest at an intermediate particle size of 25 nm, which consequently revealed the highest photoxicity. The photoactivities of the 10 and 220 nm particles as measured by EPR were comparable. We suggest that phototoxicity depends additionally on the particle–daphnia interaction area, which explains the higher photoxicity of the 10 nm particles compared to the 220 nm particles. Thus, phototoxicity is a function of the generation of different ROS and the particle–daphnia interaction area, both depending on particle size. Phototoxicity of the 10 nm and 25 nm sized nanoparticles decreased as IS of the test medium increased (EC50: 2.9 and 1.1 mg/L). In conformity with the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory we suggest that the precipitation of nano-TiO2 was more pronounced in high than in low IS medium, causing a lower phototoxicity. In summary, primary particle size and IS of the medium were identified as factors influencing phototoxicity of anatase nano-TiO2 to D. magna . Graphical abstract: Highlights: The intermediate sized particle showed the highest phototoxicity to daphnids. Phototoxicity was not related to free OH radicals only but to the generation of different ROS. Generation of different ROS and daphnia particle interaction area determine phototoxicity. Phototoxicity was less pronounced in high than in low ionic strength medium. Particle size and IS of the medium influence phototoxicity of anatase nano-TiO2 . Abstract : Primary particle size of anatase TiO2 materials and ionic strength of the test medium were identified as important factors impacting their phototoxicity to daphnids.