Toxic effects and action mechanism of metal-organic framework UiO-66-NH₂ in Microcystis aeruginosa

The zirconium metal-organic framework UiO-66-NH₂ has garnered considerable attention for their potentials of removing environmental contaminants from water. The production and application of UiO-66-NH₂ make their releases into the aquatic environment inevitable. Nevertheless, little information is available regarding its potential risk to the environment and aquatic organisms, thus limiting the evaluation of its safe and sustainable use. In this study, the ecotoxicity of UiO-66-NH₂ was evaluated, specifically its impacts on growth, extracellular organic matter release, and metabolomic changes of the model phytoplankton Microcystis aeruginosa (M. aeruginosa). UiO-66-NH₂ exhibited moderate effects on algal physiology including growth, viability, and photosynthetic system. At concentrations below 20 mg/L, UiO-66-NH₂ induced negligible inhibition of algal growth, algal viability, and photosynthesis. In contrast, UiO-66-NH₂ boosted the release of extracellular organic matter even at concentration as low as 0.02 mg/L. These findings indicated that, while no evident damage to algal cells was observed, UiO-66-NH₂ was hazardous to the aquatic environment as it stimulated the release of algal toxins. Moreover, UiO-66-NH₂ entered algal cells rather than adhering to the surface of M. aeruginosa as observed by the fluorescence imaging. Based on metabolic analysis, UiO-66-NH₂ influenced the cyanobacteria mainly through interference with purine metabolism and ABC transporter. This study sheds light on the potential threat UiO-66-NH₂ posing to microalgae, and has potential implications for its safe utilization in the environmental field. © 2024 Elsevier Ltd.