Reduced graphene oxide/magnesium oxide (RGO/MgO) nanocomposites induced toxicity in normal rat kidney cells through oxidative stress and apoptosis mechanisms

• Toxicity of RGO/MgO nanocomposites was explored in NRK-52E cells. • RGO/MgO nanocomposites cause cytotoxicity that varies with time and dose. • Nanocomposites induced oxidative stress as shown by ROS upsurge and GSH decrease. • RGO/MgO nanocomposites was found to induce apoptosis and cell cycle arrest. • This study emphasizes the importance of nanocomposites toxicity studies. Reduced graphene oxide/magnesium oxide (RGO/MgO) nanocomposites are gaining increasing attention due to their advanced characteristics that could be used in numerous areas, including biomedicine. However, there is still limited research on the toxicity of RGO/MgO nanocomposites. This study aimed to investigate the cytotoxic potential of RGO/MgO nanocomposites in normal rat kidney cells (NRK-52E), focusing on oxidative stress, apoptosis, and cell cycle regulation. RGO/MgO nanocomposite was prepared by a sonochemical method. X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), dynamic light scattering (DLS), and zeta potential were utilized to characterize synthesized samples. Results demonstrated that RGO/MgO nanocomposites induce dose- and time-dependent cytotoxicity, evident by MTT and trypan blue assays, along with morphological examinations. Oxidative stress response of this nanocomposite was shown by intracellular ROS production and declining GSH level. Immunoblotting data demonstrated that the expression level of the pro-apoptotic protein Bax was elevated while the antiapoptotic protein Bcl-2 declined following nanocomposite exposure. RGO/MgO nanocomposites also induce cleaved caspase-3 expression, an executioner caspase, and reduce the expression of Cdk-1 protein that is involved in the cell cycle. Data from cell cycle analyses and acridine orange-ethidium bromide (AO-EB) probing further confirm the apoptotic potential of this nanocomposite. The present study is the first preliminary report indicating that RGO/MgO nanocomposites induced toxicity in a non-cancerous normal cell line (NRK-52E) via oxidative stress and altered regulation of apoptotic genes. This study warrants further research on the health effects of RGO/MgO nanocomposites in appropriate in vivo model systems.