Drying of graphene oxide: effects on red blood cells and protein corona formation

In this work, we performed an integrated study on the physicochemical changes of graphene oxide (GO) during the drying process in terms of their biological effects on red blood cells (hemolysis) and interactions with human plasma (protein corona formation). GO in aqueous dispersion (GO-Disp) was dried exploring two procedures: using a vacuum system at room temperature (GO-VD) and lyophilization (GO-LP). The nanomaterials were well characterized by microscopic (TEM, SEM, and AFM), spectroscopic (FTIR, UV–Vis, Raman, and ¹³C NMR), and XRD techniques. The lyophilization process produced a nanomaterial with a three-dimensional porous macrostructure and the lowest oxidation degree. In contrast, the vacuum-drying process at room temperature provided a nanomaterial with a film-like macrostructure, presenting a higher oxidation degree as well as physicochemical properties more similar to those of GO-Disp. All of the nanomaterials adsorbed human plasma proteins; however, the protein adsorption was more selective for GO-Disp. GO-VD induced hemolysis of red blood cells in a lower concentration than GO-Disp and GO-LP, but the protein corona formation suppressed the hemolytic effect for all nanomaterials. Finally, our results indicate that the method applied to dry GO nanomaterials has a critical influence on their nanobiointeractions with cells and proteins, suggesting that more attention should be paid to biomedical applications and toxicological evaluations associated with these promising nanomaterials.