Toxicity of nZn-CuO antibacterial coating on reverse osmosis membranes in zebrafish

Among nano metal oxides, Zn-doped CuO nanocomposite (nZn-CuO) showed antibacterial activity more effective than nZnO or CuO nanoparticles, due to higher ROS production. Hence, nZn-CuO is considered a promising nanotool for coating different materials, including reverse osmosis membranes for water purification, to confer antibacterial properties. However, the effects of nZn-CuO on water purification membranes to the aquatic ecosystem health, when released into the aquatic environment, are still unknown. Consequently, this work aim is to define: 1) the eventual release of nZn-CuO in water and 2) the toxicological potential of nZn-CuO functionalized membranes on aquatic organisms. Zebrafish (Danio rerio) is widely accepted as a model for ecotoxicological studies. Organisation for Economic Co-operation and Development (OECD) recommends the Fish Embryo Acute Toxicity (FET) test (OECD n. 236) to determine toxicity of a wide variety of chemicals on zebrafish embryonic stages. Fertilized eggs are exposed to chemicals for 96 hours and different morphological indicators of lethality are recorded every 24 hours. At the end of the exposure, acute toxicity is determined based on a positive outcome in any of the observations recorded. During FET test, nZn-CuO affects zebrafish hatching and this effect likely would have an impact on development at later phases. Therefore, FET test is considered a powerful tool to evaluate Zn-doped CuO nanocomposite and reverse osmosis leachate toxicological potential in aquatic environment. Further investigations are necessary to better comprehend the real potential of nZn-CuO as an antibacterial coating for reverse osmosis membrane. Moreover, biomarkers of sublethal effect will be evaluated.