biological surface coating and molting inhibition as mechanisms of tio2 nanoparticle toxicity in daphnia magna生物表面涂层和蜕皮抑制水蚤麦格纳的二氧化钛纳米颗粒的毒性机制.pdf

Biological Surface Coating and Molting Inhibition as Mechanisms of TiO2 Nanoparticle Toxicity in Daphnia magna ´ 1 1,2 1,2 1 1 3 Andre Dabrunz , Lars Duester , Carsten Prasse , Frank Seitz , Ricki Rosenfeldt , Carsten Schilde , 1 1 Gabriele E. Schaumann , Ralf Schulz * 1 Institute for Environmental Sciences, University of Koblenz-Landau, Landau, Germany, 2 Department of Aquatic Chemistry, Federal Institute of Hydrology, Koblenz, Germany, 3 Institute for Particle Technology, Technical University of Braunschweig, Braunschweig, Germany Abstract The production and use of nanoparticles (NP) has steadily increased within the last decade; however, knowledge about risks of NP to human health and ecosystems is still scarce. Common knowledge concerning NP effects on freshwater organisms is largely limited to standard short-term (#48 h) toxicity tests, which lack both NP fate characterization and an understanding of the mechanisms underlying toxicity. Employing slightly longer exposure times (72 to 96 h), we found that suspensions of nanosized (,100 nm initial mean diameter) titanium dioxide (nTiO2) led to toxicity in Daphnia magna at nominal concentrations of 3.8 (72-h EC50) and 0.73 mg/L (96-h EC50). However, nTiO2 disappeared quickly from the ISO-medium water phase, resulting in toxicity levels as low as 0.24 mg/L (96-h EC50) based on measured concentrations. Moreover, we showed that nTiO2 (,100 nm) is significantly more toxic than non-nanosized TiO2 (,200 nm) prepared from the same stock suspension. Most importantly, we hypothesized a mechanistic chain of events for nTiO2 toxicity in D. magna that in