Stability Study of Graphene Oxide-Bovine Serum Albumin Dispersions

In this work, a stability study of dispersions of graphene oxide and graphene oxide functionalized with polyethylene glycol (PEG) in the presence of bovine serum albumin is carried out. First, a structural characterization of these nanomaterials is performed by scanning electron microscopy, atomic force microscopy, and ultraviolet visible spectroscopy, comparing the starting nanomaterials with the nanomaterials in contact with the biological material, i.e., bovine fetal serum. The different experiments were performed at different concentrations of nanomaterial (0.125-0.5 mg/mL) and BSA (0.01-0.04 mg/mL), at different incubation times (5-360 min), with and without PEG, and at different temperatures (25-40 °C). The SEM results show that BSA is adsorbed on the surface of the graphene oxide nanomaterial. Using UV-Vis spectrophotometry, the characteristic absorption peaks of BSA are observed at 210 and 280 nm, corroborating that the protein has been adsorbed. When the time increases, the BSA protein can be detached from the nanomaterial due to a desorption process. The stability of the dispersions is reached at a pH between 7 and 9. The dispersions behave like a Newtonian fluid with viscosity values between 1.1 and 1.5 mPa·s at a temperature range of 25 to 40 °C. The viscosity values decrease as the temperature increases.