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 mu g/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 mu g/mL) because most of the intracellular metabolites such as amino acids were induced at 25 mu g/mL but were inhibited at 100 mu g/mL. Pyroglutamic acid, phosphoric acid, and inositol might be used as biomarkers for evaluating the toxicity of CS-MoS2 nanosheets. Additionally, 100 mu g/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.