Comparative toxicity and environmental impact assessments of sonochemically-synthesized CuO and Zn-doped CuO nanoparticles using zebrafish and LCA tools

Nanomaterials (NMs), including nanoparticles (NPs), offer promising potential in achieving the European Commission's Green Deal goals of climate-neutral, zero-pollution and circular economy. Metal oxide NPs display antimicrobial properties, with efficacy also towards antimicrobial-resistant bacteria. Nevertheless, the increasing manufacture, use and unintended release of NMs particularly in aquatic compartments, raises concerns about their environmental sustainability and safety towards non-target organisms. Within the Safe and Sustainable by Design framework, this study compares toxicity and environmental impacts of sonochemically synthesized water-based CuO and Zn-doped CuO NPs. Zebrafish embryos were exploited in a high-throughput developmental and behavioral screening to investigate nanosafety. The Fish Embryo acute Toxicity test was used to assess the NPs aquatic toxicity potential, while behaviour was addressed by tracking embryos activity. The Life Cycle Assessment (LCA) methodology was implemented through the OpenLCA software to evaluate the environmental footprint of the NPs synthesis. Our findings showed no significative lethality at the tested concentrations (0.01-100 mg/L) (LC_{50 wCuO} > > 100 mg/L), with the exception of ZnCuO NPs 100 mg/L (LC_{50 ZnCuO} = 123 mg/L). Sub-lethality occurred as delayed hatching, partially recovered by Zn-doping, and embryo development. LCA highlighted the dominant role of electricity (which represented 47 to 98% of the total impacts) and copper acetate (37-94%) consumption in the environmental impacts of the NPs synthesis, emphasizing the importance of optimizing energy and chemical use to minimize environmental burden. This research supports the safe and sustainable design of nano-enabled antimicrobials and underscores the need for an approach comprehensive of both risk assessment and LCA in nanotechnology development.