Ti3C2Tx (MXene) disrupts growth and development in Daphnia magna by suppressing related genes and inducing gut microbiome dysbiosis

The potential risks of Ti₃C₂T_x (MXene) nanomaterials to the ecological environment and human health have drawn increasing attention due to their widespread applications in the fields of biomedicine and environmental remediation. Although the aquatic ecotoxicity of Ti₃C₂T_x has been reported, little is known about how Ti₃C₂T_x disrupts the physiological processes that regulate growth and development in zooplankton. This study investigated the toxic effects and mechanisms of Ti₃C₂T_x exposure on the growth and development of <i>Daphnia magna</i> through gene expression and gut microbiome analyses. Results show that Ti₃C₂T_x exposure significantly reduced moulting frequency, body length, body width, and absolute growth rate in <i>D. magna</i>. Exposure to Ti₃C₂T_x led to a significant decrease in the expression of growth and development-related genes (<i>cyp18a1</i>, <i>ecra</i>, <i>usp, hr3</i>, and <i>cpa1</i>) in <i>D. magna</i>. Microbiome analysis revealed that exposure to Ti₃C₂T_x resulted in a decrease in Proteobacteria and an increase in Bacteroidota in the microbial community of <i>D. magna</i>. Meanwhile, Ti₃C₂T_x induced reduced abundances of <i>Pseudomonas</i> and <i>Aeromonas</i>, as well as increased abundances of <i>Bacillus</i> and <i>Phascolarctobacterium</i>. These microbial functions primarily contribute to energy acquisition and metabolism. This study indicated that Ti₃C₂T_x can inhibit the growth and development of <i>D. magna</i> by inhibiting the expression of growth and development-related genes and inducing intestinal microbial community dysbiosis. This study provides new insights into understanding the mechanisms of Ti₃C₂T_x toxicity on the growth and development of zooplankton in aquatic ecosystems.