Ecotossicità dei nanomateriali

La diffusione nell’ambiente di nanoparticelle di molti tipi (metalliche, plastiche, ecc.) e il loro destino ambientale impongono un’accurata valutazione dei loro effetti sugli organismi viventi e sulle dinamiche naturali, in particolare negli ecosistemi marini e salmastri, destinatari ultimi di tutte le contaminazioni ambientali. Saggi ecotossicologici dedicati alla valutazione della tossicità dei nanomateriali che includono i nuovi approcci necessari a valutare le problematiche tipiche della “nanotossicologia”, come i metodi fisici di valutazione dello stato di aggregazione delle nanoparticelle, hanno dimostrato la tossicità di nanoparticelle metalliche nonostante la variazione del loro stato di aggregazione a seconda della salinità del mezzo in cui si trovano. Il saggio su Vibrio anguillarum (vedi Nuovo saggio di ecotossicità per nanomateriali), ha dimostrato chiaramente la relazione dose-effetto in risposta a concentrazioni crescenti di nanoparticelle di ossido di rame (nCuO), ma anche la variazione della tossicità con la salinità. Inoltre, in accordo con le lineeguida dell’OECD, sono state identificate la distribuzione in classi di dimensione e la stabilità delle nanoparticelle tramite due diverse tecniche, Dynamic Light Scattering e Dispersion Analysis by LUMiSizer.

Con l’obiettivo di costruire una batteria di saggi dedicati, non solo sono stati revisionati alcuni saggi già in uso ma sono anche stati progettati e provati dei nuovi modelli ecotossicologici. I saggi selezionati sono stati utililizzati per identificare le Concentrazioni Efficaci, valutando endpoint letali e sub-letali. I test di mortalità sono stati eseguiti su rotiferi (Brachionus plicatilis), crostacei (Artemia franciscana) e copepodi (Tigriopus fulvus). Mentre per i saggi sub-letali sono stati studiati: le alterazioni nella capacità di accrescimento, come numero e frequenza di mute, in Tigriopus fulvus e la capacità riproduttiva, come tasso di fecondazione, su sul riccio di mare (Paracentrotus lividus).

Questo lavoro rappresenta un punto di partenza per lo studio della tossicità delle nanoparticelle su organismi marini o alotollerranti, ed è supportato dal programma di ricerca “NanoBioTech Ambiente e Salute” (finanziato da Regione Lazio e Consorzio Hypazia) e include uno specifico accordo di progetto con l’ISPRA. Il lavoro è svolto in collaborazione con lo staff del Consorzio Hypazia, in particolare con Flavio Lucibello, presidente del Consorzio, con Loredana Manfra (Laboratorio di Ecotossicologia, ISPRA) e con Linda Prato (CNR IAMC, Taranto).

 

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.