In Vitro Pulmonary Toxicity of Reduced Graphene Oxide-Nano Zero Valent Iron Nanohybrids and Comparison with Parent Nanomaterial Attributes

Conjugation of individual nanomaterials to form "nanohybrids" has been the recent focus of advanced material synthesis with the aim to achieve enhanced properties and synergistic functionalities. However, nanohybrids may induce uncertain and unknown biological interactions and toxicological responses that are likely to be unique and altered from their component nanomaterial attributes. In this study, reduced graphene oxide-nanoscale zerovalent iron (rGO-nZVI), a multifunctional nanohybrid with promise for environmental remediation, has been systematically evaluated for in vitro toxicity to human bronchial epithelial cells (BEAS-2B). Careful synthesis of rGO-nZVI was performed by chemical coreduction of graphene oxide (GO) and iron salt precursors, followed by evaluation of their physicochemical properties and colloidal stability in the biological media. A comprehensive assessment of biological interactions and toxicological outcomes of rGO-nZVI and its parent materials, i.e., GO, rGO, and nZVI on BEAS-2B cells included cellular uptake, cell viability, cell membrane integrity, reactive oxygen species (ROS) generation, and cell cycle analyses. The toxic behavior of rGO-nZVI nanohybrids was found to be in between that of rGO/GO (most toxic) and nZVI (least toxic); however, it was majorly governed by rGO/GO toxicity and its mechanisms. This study sheds light on the importance of sustainable design strategies for the next-generation complex and hierarchical nanostructures.