Dispersibility-Dependent Biodegradation of Graphene Oxide by Myeloperoxidase

Understanding human health risk associated with the rapidly emerging graphene‐based nanomaterials represents a great challenge because of the diversity of applications and the wide range of possible ways of exposure to this type of materials. Herein, the biodegradation of graphene oxide (GO) sheets is reported by using myeloperoxidase (hMPO) derived from human neutrophils in the presence of a low concentration of hydrogen peroxide. The degradation capability of the enzyme on three different GO samples containing different degree of oxidation on their graphenic lattice, leading to a variable dispersibility in aqueous media is compared. hMPO fails in degrading the most aggregated GO, but succeeds to completely metabolize highly dispersed GO samples. The spectroscopy and microscopy analyses provide unambiguous evidence for the key roles played by hydrophilicity, negative surface charge, and colloidal stability of the aqueous GO in their biodegradation by hMPO catalysis. The dispersibility dependent biodegradation of graphene oxide (GO) is demonstrated by using oxidative catalysis of myeloperoxidase (hMPO) derived from human neutrophils in the presence of a low concentration of hydrogen peroxide. hMPO can completely degrade the most dispersible GO but failed in degrading the least dispersed (aggregated) sample. The surface charge as well as aqueous dispersiblity of the GO samples are a playing crucial role in the biodegradation by hMPO.