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Toxicity of platinum nanoparticles to freshwater algae and crustaceans Cristina Giron Delgado1, Sara Nørgaard Sørensen1, Christian Engelbrekt2 and Anders Baun1* 1 Department of Environmental Engineering, Technical University of Denmark 2 Department of Chemistry, Technical University of Denmark *[email protected] Introduction & Objectives Materials & Methods In recent years several nanoparticles types have been studied, however only few studies cover the toxic effects of platinum nanoparticles (PtNPs) to aquatic organisms. PtNPs and platinum nanostructures can improve the catalytic activity and they have been widely used in automobile catalytic converters for many years. Due to this extensive use, emission of PtNPs into the aquatic environment must be expected and the investigation of their ecotoxicity is therefore highly relevant and important. Tested material: Starch coated PtNPs of nominal size 1.7±0.2 nm Dissolved platinum reference Algal tests with green algae P. subcapitata: 48h test OECD 201 growth inhibition test 2h test Newly developed 2h 14C-assimilation inhibition test Crustacean tests with D. magna: 48h OECD 202 mobility inhibition test 48h Newly developed anti-sedimentation test: Therefore, the aim of this study is to: 1) Evaluate of the acute toxicity of PtCl4 and PtNPs towards Pseudokirchneriella subcapitata and Daphnia magna . 2) Investigate the uptake and depuration of PtNPs in Daphnia magna. Results: Algal Toxicity Results: Daphnia Toxicity 1 10 100 Concentration (mg/l) Observed values 10% effect level Lower 95% C.I. conc-level 1000 LogNorm curve fit 50% effect level Upper 95% C.I. conc-level Short term test (2h) in comparison with 48h: try to minimize the aggregation, sedimentation and possible interactions of PtNPs. Algae 48h Algae 2h 2h 0.1 1 10 100 Concentration (mg/l) Observed values 10% effect level Lower 95% C.I. conc-level PtCl4 (mg Pt/l) EC50 = 1.3 [1.1;1.5]95% Toxicity not found 1000 PtNPs mass per alive organism (µg) Regular test LC (48h) IC (48h) 0.1 1 10 100 Concentration (mg/l) LogNorm curve fit 50% effect level Upper 95% C.I. conc-level PtNPs (mg Pt/l) EC50 = 14 [13;16]95% EC50 = 28 [23;25]95% Results: Uptake / Depuration PtCl4 (mg Pt/l) Daphnia 48h (regular test) Daphnia 48h (antisedimentation test) IC50 = 1.7 [1.4;2.3]95% Not performed 1000 1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0 Net Pt Nps suspension Anti-sedimentation test LC (48h) IC (48h) 1 10 100 Concentration (mg/l) 1000 PtNPs (mg Pt/l) IC50 = 17 LC50 = 26 [21;32]95% IC50 = 31 LC50 = 34 Conclusions • Algal toxicity tests: Pt salt is more toxic than PtNPs. PtNPs are toxic within 2h and its toxicity is dependent on the time of exposure. 0.09 0.08 1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0 during 24h exposure to PtNPs during 24h in clean medium Response 48h 1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 Response 1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 Daphnia neonates Uptake and depuration test with D. Magna Uptake Depuration Inhibition Inhibition PtNPs PtCl4 1 mg PtNPs/l 0.07 0.06 • Daphnia toxicity tests: › In the regular test IC50 > LC50: significant number of animals were alive but immobile. › In the anti-sedimentation test IC50 ≈ LC50: immobilization due to particles settling is almost avoided. Reducing sedimentation, the number of died (immobile) animals are reduced too. 0.05 0.04 0.03 0.02 0.01 0.00 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 Time (h) UPTAKE DEPURATION t= 24 hours Significant increase of PtNPs in Daphnia bodies from the 6th hour to complete the 24 hours of exposure. When the animals are transferred to clean medium, a fast depuration occur. PtNPs remain inside the organisms after 24 hours depuration in clean medium. • Algae vs. daphnia toxicity: Almost similar toxicity, however algae is a bit more sensitive to both PtCl4 and PtNPs. • Uptake / Depuration study: Uptake of PtNPs in daphnia is initially slow, but increases after 6h exposure. A very fast depuration is found upon transfer to clean medium. Not all PtNPs are depurated in 24h.