Evaluation of Alpha and Gamma Aluminum Oxide Nanoparticle Accumulation, Toxicity, and Depuration in Artemia salina Larvae

摘要

In this study, Artemia salina (crustacean filter feeders) larvae were used as a test model to investigate the toxicity of aluminum oxide nanoparticles (Al_2O_3 NPs) on marine microorganisms. The uptake, toxicity, and elimination of α-Al_2O_3 (50 nm and 3.5 μm) and γ-Al_2O_3 (5 nm and 0.4 μm) NPs were studied. Twenty-four and ninety-six hour exposures of different concentrations of Al_2O_3 NPs to Artemia larvae were conducted in a seawater medium. When suspended in water, Al_2O_3 NPs aggregated substantially with the sizes ranging from 6.3 nm to ＞0.3 μm for spherical NPs and from 250 to 756 nm for rod-shaped NPs. The phase contrast microscope images showed that NPs deposited inside the guts as aggregates. Inductively coupled plasma mass spectrometry analysis showed that large particles (3.5 μm α-Al_2O_3) were not taken up by Artemia, whereas fine NPs (0.4 μm γ-Al_2O_3) and ultra-fine NPs (5 nm γ-Al_2O_3 and 50 nm α-Al_2O_3) accumulated substantially. Differences in toxicity were detected as changing with NP size and morphology. The malondialdehyde levels indicated that smaller γ-Al_2O_3 (5 nm) NPs were more toxic than larger γ-Al_2O_3 (0.4 μm) particulates in 96 h. The highest mortality was measured as 34% in 96 h for γ-Al_2O_3 NPs (5 nm) at 100 mg/L (LC_(50) ＞ 100 mg/L). γ-Al_2O_3 NPs were more toxic than α-Al_2O_3 NPs at all conditions.