Ecotoxicology of copper oxide nanomaterials on the pond snail, Lymnaea stagnalis

Abstract

Copper oxide nanomaterials (CuO NMs) are frequently employed for their antimicrobial properties in antifouling paints and other applications. Their extensive use can lead to contamination of aquatic ecosystems. In this research study, the freshwater snail, Lymnaea stagnalis, was used, as representative species, to identify biological and environmental impacts of CuO NMs on the benthic ecosystem. An holistic evaluation of the toxicity of Cu as Cu2+ and CuO NMs (as pristine and safer by design (SbyD) CuO NMs (polyvinylpyrrolidone (PVP) and ascorbate (ASC)) and CuO Fragmented Products (FP)) was conducted, via acute and chronic exposure using different life stages of L. stagnalis and biological endpoints (mortality, reproduction and behaviour studies as well as molecular response). Overall outputs demonstrated the higher sensitivity of juveniles compared to adults exposed to either ionic Cu or CuO NMs. Furthermore, data showed, in general, a higher toxicity of Cu ions compared to CuO NMs, despite equal concentration of dissolved Cu ions in solution, except for SbyD CuO-PVP functionalized in phosphate buffer. Indeed, this project demonstrated that manufacturing conditions, dispersants used and medium, have an important role in determining fate and hazard of surface coatings of NMs. Furthermore, findings showed that acute experiments results are not always reflected when chronic experiments are conducted, since the fate of the individual NMs will be different, and hazard ranking of materials might differ across different exposure types and timelines. Moreover, the non-lethal toxicity, as well as the absence of any molecular response due to exposure to CuO_FP found in this study, highlights the need for more studies assessing the risk of forms of NMs more representatives of real exposure scenarios, such as NMs embedded in their matrix, rather than solely their pristine form. Finally, promising findings were gathered using long term memory (LTM) formation test as a non-invasive endpoint to assess CuO NMs toxicity on L. stagnalis, providing an early toxicity indication compared with the more conventional LC50 approach.