Differential cytotoxicity and internalization of graphene family nanomaterials in myocardial cells

- H9c2 cells were treated with a family of graphene particles: graphene oxide (GO), low reduced GO (LRGO) and graphite.
- The cytotoxicity of GO and LRGO in H9c2 cells was studied regarding the surface content of oxygen: GO (54%) and LRGO (37%).
- GO is relatively less toxic at doses <100 μg/mL. LRGO particles showed a 5-fold increase in toxicity as compared to GO particles.

Given the well-known physical properties of graphene oxide (GO), numerous applications for this novel nanomaterial have been recently envisioned to improve the performance of biomedical devices. However, the toxicological assessment of GO, which strongly depends on the used material and the studied cell line, is a fundamental task that needs to be performed prior to its use in biomedical applications. Therefore, the toxicological characterization of GO is still ongoing. This study contributes to this, aiming to synthesize and characterize GO particles and thus investigate their toxic effects in myocardial cells. Herein, GO particles were produced from graphite using the Tour method and subsequent mild reduction was carried out to obtain low-reduced GO (LRGO) particles. A qualitative analysis of the viability, cellular uptake, and internalization of particles was carried out using GO (~ 54% content of oxygen) and LRGO (~ 37% content of oxygen) and graphite. GO and LRGO reduce the viability of cardiac cells at IC50 of 652.1 ± 1.2 and 129.4 ± 1.2 μg/mL, respectively. This shows that LRGO particles produce a five-fold increase in cytotoxicity when compared to GO. The cell uptake pattern of GO and LRGO particles demonstrated that cardiac cells retain a similar complexity to control cells. Morphological alterations examined with electron microscopy showed that internalization by GO and LRGO-treated cells (100 μg/mL) occurred affecting the cell structure. These results suggest that the viability of H9c2 cells can be associated with the surface chemistry of GO and LRGO, as defined by the amount of oxygen functionalities, the number of graphitic domains, and the size of particles. High angle annular dark-field scanning transmission electron microscopy, dynamic light-scattering, Fourier-transform infrared, Raman, and X-ray photoelectron spectroscopies were used to characterize the as-prepared materials.