Assessment of Genotoxicity Induced by Subchronic Exposure to Graphene in HaCaT Human Skin Cell Line

The applications of graphene-based materials (GBMs) and even their processing involve prolonged contact with cellular barriers such as human skin. Even though the potential cytotoxicity of graphene has been studied in recent years, the impact of long-term graphene exposure has rarely been explored. We tested in the HaCaT epithelial cells, in vitro, the effect of subchronic treatments with subletal doses of four different, well-characterized GBMs, two commercial graphene oxides (GO) and two few-layer graphenes (FLG). Cells were exposed weekly to low doses of the GBMs for 14 days, 30 days, 3 months, and 6 months. GBMs-cells uptake was assessed by confocal microscopy. Cell death and cell cycle were determined by fluorescence microscopy and cytometry, respectively. DNA damage was measured by comet assay and g-H2AX staining, followed by determination of p-p53 and p-ATR by immunolabeling. Subchronic exposure to different GBMs at non-cytotoxic doses has potential genotoxic effects on HaCaT epithelial cells, that can be recovered depending on the GBM and exposure time. Specifically, GO-induced genotoxicity can be detected after 14 and 30 days from treatment. At this time, FLG appears less genotoxic than GO, and cells can recover more easily when genotoxic pressure disappears after some days removal of the GBM. Long-term exposure, 3 and 6 months, to different GBMs induces permanent, non-reversible, genotoxic damage that is comparable than the exerted by arsenite. This should be considered for the production and future applications of GBMs in scenarios where low concentrations of the material interact chronically with epithelial barriers

Eco-friendly mechanochemical synthesis of titania-graphene nanocomposites for pesticide photodegradation

Titania graphene hybrid nanocomposites (TiO2-FLG) synthesized from graphite and TiO2 precursors, in a simple and sustainable approach via a three-step method, including the mechanochemical treatment of pre-synthesized FLG and TiO2 NPs are efficient has led to the preparation of titania graphene hybrid nanocomposites (TiO2-FLG) as efficient nano-catalysts for photocatalytic degradation of a complex mixing of pesticides (isoproturon, pyrimethanil, alachlor and methomyl). The effect of few layer graphene (FLG) loading (0-1.0%) was analyzed to define the optimal ratio of FLG to TiO2 and compared with the corresponding physical mixtures. X-ray Powder Diffraction (XRD) patterns of all these hybrid photocatalysts have presented the same crystal structure, with anatase as the main crystalline phase and brookite as secondary phase. An interaction between the graphene structure and the TiO2 nanoparticles has been observed from Energy Dispersive X-Ray (EDX), X-ray photoelectron (XPS) and Raman spectroscopy studies, indicating that FLG is mainly deposited on the surface wrapping the TiO2 nanoparticles. The presence of FLG in low concentrations and the mechanochemical activation are the key steps to improve the photocatalytic activity of TiO2 nanoparticles on these hybrid nanocomposites. The TiO2-FLG-0.5% hybrid nanocomposite, with circa 1.9 % content of graphitic carbon in surface, has showed the best photocatalytic performance in the degradation of pesticides. Pesticides were completely removed at 350 minutes, and around 82 % of total organic carbon (TOC) conversion was achieved at 540 minutes of irradiation time