Safety assessment of graphene acid and cyanographene: Towards new carbon-based nanomedicine

Graphene oxide (GO) has been intensively studied in last decades as a promising delivery nanoplatform. Although it surpasses the pristine graphene in its hydrophilic properties, variability in GO syntheses and chemical composition, its non-specific surface properties and heterogeneity in colloidal stability hamper its commercial application in general. Reliable cytotoxicity investigation of new nanotherapeutics under relevant physiological conditions represents an indispensable first step for their potential clinical translation. In the case of delivery nanoplatforms, the vasculature represents the first encounter after intravenous application. Therefore, an evaluation of interaction with endothelial and immune cells is highly desirable. Here, we performed a first comprehensive safety assessment of emerging graphene derivatives with high potential in biomedical technologies: graphene acid (GA) and cyanographene (GCN). We utilized an easy-to-use co-culture model of matured human umbilical vein endothelial cells (HUVECs) and a human monocyte/macrophage like cell line (THP-1) under dynamic flow conditions. An environment that has not been used yet to evaluate any graphene material. Our results demonstrate that well-defined synthesis/structure of GA and GCN overcome some drawbacks of graphene oxide (GO), the benchmark graphene derivative. Furthermore, applying a system mimicking a simplified blood vessel, both GA and GCN showed excellent biocompatibility without any indication of acute inflammation or dysfunction of endothelium. In summary, GA and GCN display so far all desirable properties to be potentially utilized in drug/gene delivery applications compared to the conventional GO.