Ecotoxicity of nanomaterials

The diffusion in the environment of several types of nanoparticles (metallic, plastic, etc.) and their environmental fate require a careful evaluation of the effects on living organisms or natural ecosystem dynamics, particularly the marine and brackish ones, final sink of all contaminants. Dedicated tests for the ecotoxicological evaluation of nanomaterials demonstrated the toxicity of metal nanoparticles and included the physical methods to evaluate the aggregation state of nanoparticles, according to salinity of the medium.
The assay on Vibrio anguillarum (see New ecotoxicity tests for nanomaterials) has shown clearly the dose effect relationship in response to increasing concentrations of copper oxide nanoparticles (nCuO), but also the variation of toxicity with salinity. In agreement with the OECD guidelines, the distribution in size classes and the stability of nanoparticles have been identified by two different techniques, Dynamic Light Scattering and Dispersion Analysis by LUMiSizer.

To build a dedicated battery of ecotoxicological tests, some already used tests were revised and tested for the new ecotoxicological aims. The selected bioassays use standard protocols to identify the Effective Concentrations, by assessing lethal and sub-lethal endpoints. Lethal acute tests were performed on rotifers (Brachionus plicatilis), crustaceans (Artemia franciscana) and copepods (Tigriopus fulvus). Moult release failure and fertilization rate were studied, as sub-lethal endpoints, on T. fulvus and sea urchin (Paracentrotus lividus), respectively.

 

Gallo A., Manfra L., Boni R., Rotini A., Migliore L., Tosti E. (2018) - CYTOTOXICITY AND GENOTOXICITY OF CUO NANOPARTICLES IN SEA URCHIN SPERMATOZOA THROUGH OXIDATIVE STRESS. Environmental International, 118: 325-333 DOI: 10.1016/j.envint.2018.05.034

Copper oxide nanoparticles (CuO NPs) are extensively used in various industrial and commercial applications. Despite their wide application may lead to the contamination of marine ecosystem, their potential environmental effects remain to be determined. Toxicity assessment studies have primarily focused on investigating the effects of CuO NPs on fertilization success and embryo development of different sea urchin species while the impact on sperm quality have never been assessed. In this line, this study aims to assess the effects of CuO NPs on the spermatozoa of the sea urchin Paracentrotus lividus.

After sperm exposure to CuO NPs, biomarkers of sperm viability, cytotoxicity, oxidative stress, and genotoxicity as well as morphology were evaluated. Results showed that CuO NPs exposure decreased sperm viability, impaired mitochondrial activity and increased the production of reactive oxygen species (ROS) and lipid peroxidation. Furthermore, CuO NPs exposure caused DNA damage and morphological alterations. Together with the antioxidant rescue experiments, these results suggest that oxidative stress is the main driver of CuO NP spermiotoxic effects. The mechanism of toxicity is here proposed: the spontaneous generation of ROS induced by CuO NPs and the disruption of the mitochondrial respiratory chain lead to production of ROS that, in turn, induce lipid peroxidation and DNA damage, and result in defective spermatozoa up to induce sperm cytotoxicity. Investigating the effects of CuO NPs on sea urchin spermatozoa, this study provides valuable insights into the mechanism of reproductive toxicity induced by CuO NPs.

Rotini A., Gallo A., Parlapiano I., Berducci M.T., Boni R., Tosti E., Prato E., Maggi C., Cicero A.M., Migliore L., Manfra L. (2018) - INSIGHTS INTO THE CuO NANOPARTICLE ECOTOXICITY WITH SUITABLE MARINE MODEL SPECIES. Ecotoxicology and Environmental Safety, 147:852-860. DOI: 10.1016/j.ecoenv.2017.09.053

Metal oxide nanoparticles, among them copper oxide nanoparticles (CuO NPs), are widely used in different applications (e.g. batteries, gas sensors, superconductors, plastics and metallic coatings), increasing their potential release in the environment. In aquatic matrix, the behavior of CuO NPs may strongly change, depending on their surface charge and some physical-chemical characteristics of the medium (e.g. ionic strength, salinity, pH and natural organic matter content). Ecotoxiticy of CuO NPs to aquatic organisms was mainly studied on freshwater species, few tests being performed on marine biota. The aim of this study was to assess the toxicity of CuO NPs on suitable indicator species, belonging to the ecologically relevant level of consumers. The selected bioassays use standard protocols to identify Effective Concentrations, by assessing lethal and sub-lethal endpoints. Mortality tests were performed on rotifer (Brachionus plicatilis), shrimp (Artemia franciscana) and copepod (Tigriopus fulvus). While moult release failure and fertilization rate were studied, as sub-lethal endpoints, on T. fulvus and sea urchin (Paracentrotus lividus), respectively. The size distribution and sedimentation rates of CuO NPs, together with the Cu2+ dissolution, were also analysed in the exposure media. The CuO NP ecotoxicity assessment showed a dose-dependent response for all species, indicating similar mortality for B. plicatilis (48hLC50=16.94±2.68 mg/l) and T. fulvus (96hLC50=12.35±0.48 mg/l), followed by A. franciscana (48hLC50=64.55±3.54 mg/l). Comparable EC50 values were also obtained for the sub-lethal endpoints in P. lividus (EC50=2.28±0.06 mg/l) and T. fulvus (EC50=2.38±0.20 mg/l). Cu2+ showed higher toxicity than CuO NPs for all species, with common sensitivity trend as follows: P. lividusT. fulvus (sublethal endpoint) ≥ B. plicatilis > T. fulvus (lethal endpoint) > A. franciscana. CuO NP micrometric aggregates and high sedimentation rates were observed in the test media, with different particle size distributions depending on the medium. The Cu2+ dissolution was about 10 % of the initial concentration, comparable to literature values, but not accounting for the toxicity of NP suspensions. The integrated ecotoxicological-physicochemical approach was used to better describe CuO NP toxicity and behavior. In particular, the successful application of ecotoxicological standard protocols allowed to produce reliable L(E)C50 data useful to identify thresholds and assess potential environmental hazard due to NPs.

 

This work is a starting point in the evaluation of nanoparticles toxicity on marine or brackish organisms. It is supported by the Research Program "NanoBioTech Environment and Health" (funded by Regione Lazio and Consorzio Hypazia) and include project agreement with ISPRA. The work is done in collaboration with the staff of the Consorzio Hypazia, in particular with Flavio Lucibello, President of the Consorzio, with Loredana Manfra (Laboratory of Ecotoxicology, ISPRA) and Linda Prato (CNR IAMC, Taranto).