Effects of Ti3C2Tx (MXene) on growth, oxidative stress, and metabolism of Microcystis aeruginosa†

The potential ecotoxicity of Ti₃C₂T_x (MXene) is becoming a growing concern due to its widespread use in the field of environmental remediation. Unfortunately, little is known about the toxic effects and mechanisms of Ti₃C₂T_x on aquatic phytoplankton. Herein, we investigated the influence of Ti₃C₂T_x on the growth, oxidative stress, and metabolism of the phytoplankton Microcystis aeruginosa using conventional toxicological and metabolomics methods. Results showed that Ti₃C₂T_x had a dose-dependent effect on the physiological ecology of M. aeruginosa. Although low Ti₃C₂T_x concentrations (≤1 mg L⁻¹) did not significantly change the M. aeruginosa growth, oxidative status, and cell morphology, high concentrations (≥5 mg L⁻¹) substantially reduced its proliferation and photosynthetic capacity. The metabolomics results showed that low (1 mg L⁻¹) and high (5 mg L⁻¹) Ti₃C₂T_x concentrations induced the expression of 43 and 128 differential metabolites in M. aeruginosa, respectively, which were mainly enriched in the amino acid metabolism and lipid metabolism pathways. These results suggest that Ti₃C₂T_x resulted in metabolic disorders in M. aeruginosa, such as porphyrin and chlorophyll metabolism and glycerophospholipid metabolism, thereby inhibiting the photosynthetic activity of M. aeruginosa and ultimately leading to a decrease in algal growth. This study provides new insights into the toxicity mechanism of Ti₃C₂T_x against M. aeruginosa, which helps us understand the potential risks of Ti₃C₂T_x in the aquatic environment.