Tailored graphene nanoparticles for biomedical application: preliminary in vitro characterization of the functionality in model cell lines

This is the authors' abstract. We don't add key points for this paper.

• GNPs water dispersions are prepared from environment-friendly physical method. • GNPs consist in few graphene layers (N < 10) with lateral size < L> ≈ 10 2 nm. • Structure/property correlations through UV–vis, FTIR, Raman spectra, DLS and TEM. • GNPs do not enter in HT1376 carcinoma cells of epithelial origin. • TOP60 GNPs are internalized by U373 astrocytoma cells without affecting cell death. • TOP60 GNPs do not trigger an inflammatory response in vitro. Thanks to an environmentally friendly physical treatment of high purity graphite, a good control of the structure of graphene nanoparticles (GNPs) has been obtained with the production of stable and reproducible GNPs water dispersions. The preparation protocol entailed ball-milling of synthetic graphite followed by sonication in water and centrifugation/separation procedures. This way, two different GNPs samples with slightly different structural characteristics were harvested: TOP60, showing an average lateral size of the graphene layers < L> = 70 nm and average number of stacked layers < N> = 4, and BOTTOM60, with < L> = 120 nm and < N> = 6. A detailed structural characterization of GNPs was performed as mandatory pre-requisite to build reliable structure/properties correlations, in terms of both bio-medical efficacy and toxicity, aiming at a rationale design of tailored materials for applications in biological environments. To this end, in this study GNPs were thoroughly characterized, focusing on cytotoxicity, cellular up-take, and inflammatory response, by testing their effect in different cell lines. BOTTOM60 GNPs in culture medium and in the presence of cells showed a tendency to form big aggregates, phenomenon that was probably responsible for their cytotoxicity at high concentrations. On the other hand, TOP60 GNPs showed a diverse behavior depending on the cell type under investigation. Indeed, the nanoparticles were internalized by cells specialized in endo/phagocytosis, such as astrocytoma cells, but not by carcinoma cells of epithelial origin. Moreover, TOP60 GNPs caused a reduction of proliferation only at high concentration and did not trigger an inflammatory response in THP-1-derived macrophages. The evidence here collected paves the way for further investigations towards the development of GNPs-based drug delivery systems.