Can the sonication of polystyrene nanoparticles alter the acute toxicity and swimming behavior results for Daphnia magna?

The seemingly ubiquitous presence of plastic debris led to a greater focus on micro- and nanoplastics research derived from the degradation process of macroplastics. The ingestion and consequent accumulation of plastics on the biota are the main concerns. Researchers strive to make assay conditions as close as possible to those of the environment. In this regard, sonication can be applied to de-agglomerate the plastic particles, but this may alter significantly their toxicity. The aim of this study was to understand the effects of the sonication process on the acute toxicity and swimming behavior of polystyrene nanoparticles using Daphnia magna as the test organism. The results show a 2-fold reduction in the acute toxicity after the sonication process; the EC50 of the PSNP-NS was 1.28 ± 0.17 mmol while for PSNP-S the EC50 was 2.77 ± 0.32 mmol, possibly through the formation of an eco-corona on the nanoplastic surface, formed from the ions dispersed in the medium or proteins secreted by the test organisms. The mean swimming distance was reduced when compared to the control group for both the PSNP-S and PSNP-NS. This is the first research stating the toxicological differences between sonicated and non-sonicated polystyrene nanoparticle samples using Daphnia magna as test organism.

Toxicological effects of AgNPs on duckweed (Landoltia punctata).

Silver nanoparticles (AgNPs) are widely applied in several types of products since they act as a biocide. However, their high level of release into the environment can bring risks to ecosystems. Thus, the toxicity of AgNPs toward duckweed (Landoltia punctata) was investigated by monitoring the growth rate inhibition and the effect on the photosynthetic metabolism through morphological and ultrastructural analysis. The AgNPs were characterized by transmission electron microscopy and the effective diameter (dynamic light scattering) and zeta potential were determined. Plants were grown according to the environmental conditions recommended in ISO/DIS 20079 and then exposed to different concentrations of AgNPs. Inhibition of the growth rate was measured based on the EC50 and changes in the morphology, cellular structures and photosynthetic pigments were evaluated along with the silver accumulation. Although the results showed low growth inhibition when compared to other studies, significant damage to the ultrastructure, decreases in the photosynthetic pigments and starch grains, an increase in the phenolic compounds and physiological changes, such as a loss of color, were observed. Moreover, the accumulation of silver ions was noted and this could lead to bioamplification in consumer organisms, since duckweed belongs to the first level of the food chain.

Comparison of cytotoxicity of α-Al2O3 and η-Al2O3 nanoparticles toward neuronal and bronchial cells.

The role of the crystalline structure on the toxicity of two phases of Al2O3 NPs, alpha (α-Al2O3 NPs) and eta (η-Al2O3 NPs), was investigated in this study. Different techniques were employed for the characterization of the Al2O3 NPs and multiple toxicological endpoints were used to assess the toxicity toward mouse neuroblastoma (N2A) and human bronchial epithelial (BEAS-2B) cells. Based on the results of the multiple toxicological endpoints, revealed differences in the toxic potential results for α-Al2O3 NPs and η-Al2O3 NPs, with the latter showing a more pronounced effect. These effects could be due to the high uptake of the η-Al2O3 NPs in the cytoplasmic vesicles, as evidenced by TEM and ICP-MS. Hence, the results demonstrate the potential toxicity of both α-Al2O3 NPs and η-Al2O3 NPs, although the N2A and BEAS-2B cells showed greater susceptibility toward η-Al2O3 NPs. Thus, our study demonstrates the important role of the crystalline structure in relation to the nanotoxicity of Al2O3 NPs.

Synthesis, characterization and toxicological evaluation of Cr2O3 nanoparticles using Daphnia magna and Aliivibrio fischeri.

Chromium III oxide (Cr2O3) nanoparticles (NPs) are used in pigments for ceramics, dyes, paints and cosmetics. However, few studies addressing the toxic potential of these NPs have been reported in the literature. Thus, this research aimed to evaluate the acute and chronic effects of Cr2O3 NPs through acute toxicity tests with Daphnia magna and Aliivibrio fischeri and chronic toxicity tests with Daphnia magna. Cr2O3 NPs were synthesized by the sol-gel method and characterized through TEM, X-Ray diffraction (XRD), zeta potential (ZP) and surface area analysis. In the acute toxicity tests the EC(50,48h) value obtained with D. magna was 6.79 mg L(-1) and for A. fischeri the EC(50,15min) value was 16.10 mg L(-1) and the EC(50,30min) value was 12.91 mg L(-1). Regarding the chronic toxicity tests with D. magna, effects on longevity (OEC=1.00 mg L(-1)), reproduction (OEC=1.00 mg L(-1)) and growth (OEC=0.50 mg L(-1)) were observed. On the SEM and TEM images, ultrastructural alterations in the organelles of exposed organisms were also observed. Thus, toxicological studies with NPs are of great importance in order to reduce the risk of environmental contamination.

Toxicological effects of copper oxide nanoparticles on the growth rate, photosynthetic pigment content, and cell morphology of the duckweed Landoltia punctata.

Recently, the application of copper oxide nanoparticles (CuO-NPs) has increased considerably, primarily in scientific and industrial fields. However, studies to assess their health risks and environmental impacts are scarce. Therefore, the present study aims to evaluate the toxicological effects of CuO-NPs on the duckweed species Landoltia punctata, which was used as a test organism. To accomplish this, duckweed was grown under standard procedures according to ISO DIS 20079 and exposed to three different concentrations of CuO-NPs (0.1, 1.0, and 10.0 g L(-1)), with one control group (without CuO-NPs). The toxicological effects were measured based on growth rate inhibition, changes in the plant's morphology, effects on ultrastructure, and alterations in photosynthetic pigments. The morphological and ultrastructural effects were evaluated by electronic, scanning and light microscopic analysis, and CuO-NPs were characterized using transmission electron microscopy (TEM), zeta potential, and superficial area methods of analysis. This analysis was performed to evaluate nanoparticle size and form in solution and sample stability. The results showed that CuO-NPs affected morphology more significantly than growth rate. L. punctata also showed the ability to remove copper ions. However, for this plant to be representative within the trophic chain, the biomagnification of effects must be assessed.

Synthesis, characterization and toxicological evaluation of a core-shell copper oxide/polyaniline nanocomposite.

The newest generation of copper oxide NPs (CuO NPs) is the CuO core-shell (CS), which has potential applications in several areas (e.g., electronics and paint) and is able to provide a greater service life due to its coating; however, its toxicity is not fully understood. The objective of this study was to synthesize, characterize and evaluate the aquatic toxicology of CuO NPs and CuO core-shells through acute and chronic toxicity tests with the freshwater microcrustaceans Daphnia magna and to evaluate its acute toxicity with the marine bioluminescent bacteria Vibrio fischeri. The NPs were synthesized by direct thermal decomposition after being coated as a CS with polyaniline (PANI). With respect to acute toxicity with D. magna, the CuO NPs and CS CuO/PANI presented EC50 values of 0.32 mg L(-1) and 0.48 mg L(-1), respectively. For the tests with V. fischeri, the CuO NPs (EC50-15 min=7.79 mg L(-1)) exhibited behavior similar to that of the CS CuO/PANI (EC50-15 min=9.05 mg L(-1)) after 15 min of exposure. Regarding chronic toxicity, both forms showed a statistically significant effect (p<0.05) on the growth and reproduction parameters. Based on the characterization and toxicity results, it can be concluded that both forms of CuO were toxic and presented similar behaviors during the acute tests; however, after 21 d of exposure, CS CuO/PANI showed higher toxicity to the reproduction parameter, highlighting the importance of a complete study of the NP to better understand its toxicity mechanism.