Graphene Quantum Dots Induce Autophagy and Reveal Protection Against Hydrogen Peroxide-Induced Oxidative Stress...

As zero-dimension nanomaterials, graphene quantum dots (GQDs) have the excellent characteristics of graphene as well as photoluminescence (PL) features that ordinary graphene does not possess for its virtue of quantum confinement effect and boundary effect, which attract lots of researchers interested in the field of biomedical applications. In this work, we found GQDs can be internalized into SGC-7901 cells, and the labeled cells exhibited bright yellow fluorescence in the form of aggregated dots. Meanwhile, GQDs effectively mitigated the injury hydrogen peroxide (H₂O₂)-induced in SGC-7901 cells including cytotoxicity and apoptosis. While H₂O₂ exposure increased ROS and decreased mitochondrial membrane potential, it could be arrested by GQDs. Furthermore, GQDs showed protective effects against the reduction of the ratio of mitochondrial apoptosis-related proteins Bcl-2/Bax in SGC-7901 cells. Our work revealed that GQDs had the antioxidant ability against oxidative stress, which meant they had the potential to be an antioxidants. Besides, GQDs increased the level of autophagy-related protein LC3-II and induced autophagic structure observed via TEM, and subsequent the results of LC3 turnover and p62 degradation demonstrated GQDs treatment led to the activation of autophagic flux. Ultimately, GQDs were found to affect autophagy through the mTOR signaling pathway.