Evaluation of alpha and gamma aluminum oxide nanoparticle accumulation, toxicity, and depuration in Artemia salina larvae

Abstract

In this study, Artemia salina (crustacean filter feeders) larvae were used as a test model to investigate the toxicity of aluminum oxide nanoparticles (Al2O3 NPs) on marine microorganisms. The uptake, toxicity, and elimination of α-Al2O3 (50 nm and 3.5 μm) and γ-Al2O3 (5 nm and 0.4 μm) NPs were studied. Twenty-four and ninety-six hour exposures of different concentrations of Al2O3 NPs to Artemia larvae were conducted in a seawater medium. When suspended in water, Al2O3 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-Al2O3) were not taken up by Artemia, whereas fine NPs (0.4 μm γ-Al2O3) and ultra-fine NPs (5 nm γ-Al2O3 and 50 nm α-Al2O3) accumulated substantially. Differences in toxicity were detected as changing with NP size and morphology. The malondialdehyde levels indicated that smaller γ-Al2O3 (5 nm) NPs were more toxic than larger γ-Al2O3 (0.4 µm) particulates in 96 h. The highest mortality was measured as 34% in 96 h for γ-Al2O3 NPs (5 nm) at 100 mg/L (LC50 > 100 mg/L). γ-Al2O3 NPs were more toxic than α-Al2O3 NPs at all conditions.

Keywords: Artemia; accumulation; aluminum oxide; nanoparticles; oxidative stress; toxicity.

Figure 1

Powdered XRD spectrum for Al₂O₃ nanoparticles (A: α-Al₂O₃ 50 nm; B: α-Al₂O₃ 3.5 μm; C: γ-Al₂O₃ 5nm; D: γ-Al₂O₃ 0.4 μm) sample.

Figure 1

Powdered XRD spectrum for Al₂O₃ nanoparticles (A: α-Al₂O₃ 50 nm; B: α-Al₂O₃ 3.5 μm; C: γ-Al₂O₃ 5nm; D: γ-Al₂O₃ 0.4 μm) sample.

Figure 1

Powdered XRD spectrum for Al₂O₃ nanoparticles (A: α-Al₂O₃ 50 nm; B: α-Al₂O₃ 3.5 μm; C: γ-Al₂O₃ 5nm; D: γ-Al₂O₃ 0.4 μm) sample.

Figure 1

Powdered XRD spectrum for Al₂O₃ nanoparticles (A: α-Al₂O₃ 50 nm; B: α-Al₂O₃ 3.5 μm; C: γ-Al₂O₃ 5nm; D: γ-Al₂O₃ 0.4 μm) sample.

Figure 2

The images of α-Al₂O₃ and γ-Al₂O₃ nanoparticles (A: α-Al₂O₃ 50 nm; B: α-Al₂O₃ 3.5 μm; C: γ-Al₂O₃ 5nm; D: γ-Al₂O₃ 0.4 μm).

Figure 2

The images of α-Al₂O₃ and γ-Al₂O₃ nanoparticles (A: α-Al₂O₃ 50 nm; B: α-Al₂O₃ 3.5 μm; C: γ-Al₂O₃ 5nm; D: γ-Al₂O₃ 0.4 μm).

Figure 2

The images of α-Al₂O₃ and γ-Al₂O₃ nanoparticles (A: α-Al₂O₃ 50 nm; B: α-Al₂O₃ 3.5 μm; C: γ-Al₂O₃ 5nm; D: γ-Al₂O₃ 0.4 μm).

Figure 2

The images of α-Al₂O₃ and γ-Al₂O₃ nanoparticles (A: α-Al₂O₃ 50 nm; B: α-Al₂O₃ 3.5 μm; C: γ-Al₂O₃ 5nm; D: γ-Al₂O₃ 0.4 μm).

Figure 3

Phase contrast microscope images of the nanoparticles inside Artemia larvae. (A: The guts are empty in controls. B: Nanoparticles are visible as a dark line inside the guts of treatments).

Figure 3

Phase contrast microscope images of the nanoparticles inside Artemia larvae. (A: The guts are empty in controls. B: Nanoparticles are visible as a dark line inside the guts of treatments).

Figure 4

Accumulation and elimination (in 24 h) profiles of α-Al₂O₃ (a) and γ-Al₂O₃ (b) nanoparticles by Artemia larvae for 24 h and 96 h exposure (μg/g).

Figure 4

Accumulation and elimination (in 24 h) profiles of α-Al₂O₃ (a) and γ-Al₂O₃ (b) nanoparticles by Artemia larvae for 24 h and 96 h exposure (μg/g).

Figure 5

Percent mortality rates for Artemia salina larvae from exposure to α-Al₂O₃ and γ-Al₂O₃ particles for 24 h and 96 h.

Figure 6

Malondialdehyde levels measured in Artemia larvae exposed to α-Al₂O₃ and γ-Al₂O₃ nanoparticles for 24 h and 96 h exposure (nmol/g)