Dispersible MoS₂ Nanosheets Activated TGF-β/Smad Pathway and Perturbed the Metabolome of Human Dermal Fibroblasts

In postgraphene two-dimensional materials (2DMs), MoS₂ has attracted increasing attention in the biomedical field due to its excellent physicochemical properties. However, the toxicity and biocompatibility evaluation of MoS₂ is not fully addressed. Herein, chitosan functionalized MoS₂ (CS-MoS₂) nanosheets, which showed perfect dispersibility and stability performances, were synthesized and characterized. We found that CS-MoS₂ nanosheets inhibited the viability of human dermal fibroblasts (HDFs) moderately while causing cell membrane instability, ROS generation, and DNA damage in a dosage-dependent manner. CS-MoS₂ nanosheets did not induce significant changes in the cell morphologies, but they seemed to impair the cell division of HDFs. CS-MoS₂ nanosheets (100 μg/mL) activated EGFR and induced reactive oxygen species, Smad, and IL-1, which in turn led to cell inflammation and apoptosis. Furthermore, HDFs showed cellular stress responses when they were exposed to low concentrations of CS-MoS₂ nanosheets (25 and 100 μg/mL) because most of the intracellular metabolites such as amino acids were induced at 25 μg/mL but were inhibited at 100 μg/mL. Pyroglutamic acid, phosphoric acid, and inositol might be used as biomarkers for evaluating the toxicity of CS-MoS₂ nanosheets. Additionally, 100 μg/mL CS-MoS₂ nanosheets inhibited glutathione metabolism and induced the imbalance of cellular redox homeostasis. It further suppressed the tricarboxylic acid cycle and other metabolic pathways, causing insufficient supply of substrates and energy for HDFs. These findings will fuel the risk assessment of MoS₂ and other 2DMs and guide the safe material design and 2DM applications.