Impact of black phosphorus nanosheet exposure on growth, reproduction, antioxidant mechanisms, and transcriptomic responses in Daphnia magna.

Black phosphorus nanosheets (BPNS), a novel two-dimensional nanomaterial, have garnered significant attention in biomedical and technological applications due to their exceptional physicochemical properties. However, their widespread use raises concerns about potential environmental risks. In this study, we elucidate the toxicological mechanisms of BPNS on Daphnia magna (D. magna), a model aquatic organism. The results reveal that BPNS is efficiently absorbed and accumulates in the intestinal tract of D. magna. Exposure to low concentrations of BPNS significantly alters developmental and reproductive performance, as evidenced by a 2-day acceleration in the time to first brood and an increase in body length from 3.1 to 3.3 mm. Furthermore, BPNS exposure induces oxidative stress in D. magna, characterized by elevated reactive oxygen species (ROS) levels, enhanced activities of superoxide dismutase (SOD) and catalase (CAT), and increased malondialdehyde (MDA) concentrations. RNA sequencing analysis indicates that dysregulation of iron homeostasis plays a pivotal role in mediating oxidative stress in D. magna. Concurrently, detoxification mechanisms are activated, as evidenced by upregulation of genes associated with chitin and carbohydrate metabolism, as well as cuticle structure components. Additionally, BPNS exposure modulates key signaling pathways, including the lysosomal pathway, starch and sucrose metabolism, and steroid biosynthesis, which collectively enhance the stress tolerance of D. magna. These findings provide critical insights into the ecological implications of BPNS release into aquatic ecosystems, highlighting the need for comprehensive risk assessments of emerging nanomaterials.