Cell Toxicity and Autophagy in A549 Cells Treated With Surface‐Functionalized Graphene Derivatives

Graphene oxide and its derivatives have unique physical and chemical properties with applications in many different fields. However, their biological effects and mechanisms of intracellular toxicity have not been completely clarified. In this study, we investigated the cytotoxic and autophagic activities of graphene oxide and its derivatives in A549 human lung carcinoma cells. In the experimental procedure, A549 cells were treated with graphene oxide (GO), dodecylamine-oxidized graphene (DA-GO), reduced graphene oxide (rGO), and sodium dodecyl sulfate-reduced graphene oxide (SDS-rGO), and their cytotoxicity and protein expression levels were measured. Treating A549 cells with each type of graphene induced a concentration-dependent toxic effect on the cells, with no obvious cytotoxicity at low concentrations (32 𝜇g/mL). However, those treated with graphene with dodecylamine and sodium dodecyl sulfate functional groups exhibited high toxicity compared to its native form at high concentrations (> 100 𝜇g/mL). Cells exposed to the graphene materials exhibited increased conversion of LC3A/B-I to LC3A/B-II depending on concentration, indicating increased autophagy activity. They also exhibited reduced levels of mTOR protein, a negative regulator of autophagy, compared to a control group for all graphene materials. However, concentrations of beclin-1, a positive regulator of autophagy, were lower for all types of GO. These findings suggest that graphene exposure may induce beclin-1-independent autophagy in a noncanonical manner. We hypothesize that this may be a result of the involvement of apoptosis-associated substances that suppress autophagy. However, the exact mechanisms of the autophagy process are not well understood, and further research remains necessary.