Nano-biointeractions of PEGylated and bare reduced graphene oxide on lung alveolar epithelial cells: A comparative in vitro study

Graphene and its derivatives have garnered significant scientific interest and have potential use in nano-electronics as well as biomedicine. However the undesirable biological consequence, especially upon inhalation of the particle, requires further investigations. This study aimed to elucidate the nano-biointeractions of PEGylated reduced graphene oxide (PrGO) and reduced graphene oxide (rGO) with that of lung alveolar epithelial cells (A549). Both nanomaterials showed dose dependent decrease in cell viability and alteration of cell morphology after 24 h. Upon intracellular uptake of PrGO, it elicited oxidative stress mediated apoptosis in the cells by inducing ROS, loss of mitochondrial membrane potential (MMP) and inflammatory response by NF-kappa B activation. Conversely, rGO was found to scavenge ROS efficiently except at high dose after 24 h. It was found that ROS at high dose of rGO prompted loss of MMP. rGO was found to adhere to the cell membrane, where it is assumed to bind to cell surface Toll like receptors (TLRs) thereby activating NF-kappa B mediated inflammatory response. All these events culminated in an increase in apoptosis of A549 cells after 24h of rGO exposure. It was also noticed that both the nanomaterials did not initiate lysosomal pathway but instead activated mitochondria mediated apoptosis. This study highlights the possible adverse toxic effect of PrGO and rGO upon inhalation and persistence of these particles in the lungs. Further research is required to comprehend the biological response of PrGO and rGO so as to advance its biomedical application and safety. (C) 2015 Elsevier B.V. All rights reserved.