Metal–phenolic network-coated nanoparticles mitigate CuO nanotoxicity

Abstract

Copper is widely used to control various plant diseases and recent trends highlight the prominence of copper-based nanomaterials in developing new nanoagrochemicals. As these nanomaterials eventually end up in the aquatic environment, they necessitate increased attention regarding their environmental and human health risks. Herein, we demonstrate the use of metal–phenolic network (MPN) nanocomposites as novel agents for mitigating the toxicity of copper oxide (CuO) nanoparticles (NPs), which exert toxicity mainly through released Cu ions. Iron–tannic acid-based porous 3D networks on gold NP cores (Fe–TA@Au NPs) exhibited the capacity to reduce CuO NP toxicity in freshwater protozoa Tetrahymena thermophila – a model for environmental toxicity, and in human macrophages – an in vitro model for human safety. In the macrophage assays, Fe–TA@Au NPs increased the half-effective concentration (EC₅₀) of CuO NPs by approximately three-fold, from 4.7 mg L⁻¹ to 15.4 mg L⁻¹. This mitigation occurred through two main mechanisms: adsorption of Cu ions, released from CuO NPs, and reduction of intracellular reactive oxygen species, both of which contributed to the toxicity of CuO NPs. The maximum adsorption capacity for Cu²⁺ was 172 mg g⁻¹ of Fe–TA MPN, comparable to other copper adsorbents, including MPNs and metal–organic frameworks (MOFs). Additionally, Fe–TA@Au NPs demonstrated excellent biocompatibility and ecosafety in a highly sensitive microalgal growth inhibition assay and exhibited long-term efficacy, indicating the strong potential of these porous materials in mitigating copper toxicity. Furthermore, the gold NP cores in the MPN model used in this study can easily be replaced with other core NP materials, making them suitable for large-scale environmental and human health applications.