The discovery of graphene boosted an interdisciplinary research based on its unique properties and possible applications in biomedicine. Multiple scientific reports concerning graphene interactions with adherent cells showed the potential use of graphene as a biomaterial in tissue engineering.In this study we examined the influence of pristine graphene, as a monolayer coating or flake suspension, on human endothelial cells (HUVEC) isolated from umbilical veins. Umbilical cords were obtained from healthy gravidas after the cesarean section procedures. Cytotoxicity, proliferation and cell morphology study were performed using various methods, including colorimetric and luminescent cell assays, optical and fluorescence microscopy.The cytotoxicity assay confirmed dose and time dependent cytotoxicity of tested graphene flakes (G1APS~5000nm and G2APS~450nm). Even the lowest concentration of graphene (10μg/ml) significantly inhibited cell proliferation. The difference between the two tested flake sizes was more distinct during cell mortality study, indicating the greater cytotoxic effect of the smaller graphene particles. Graphene suspended in the cell culture medium created aggregates. Cell imaging revealed efficient accumulation of nanoflakes inside the cells, especially those of the smaller size.The morphology of the cells seeded on graphene‐coated SiO2 substrates was recorded using fluorescence microscopy. Endothelial cells were immunostained for actin cytoskeleton to characterize its organization, stress fibers creation, cell adhesion and spreading. After a 72h incubation, both the cells incubated on graphene SiO2 substrates and on the reference material for cell plating, reached confluence. No difference in cell shape and morphology was detected. Graphene was shown to be a suitable surface for endothelial cell growth.Our preliminary investigation confirmed cytotoxic effect of pristine graphene flakes on adherent cells, however demonstrated that CVD grown graphene is not toxic for human endothelial cells. These data show promise for using graphene monolayers in tissue engineering or as a substrate material for implant devices.Support or Funding InformationWUM grant: 2M2‐W2‐16This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.