Highly efficient catalytic scavenging of oxygen free radicals with graphene-encapsulated metal nanoshields

Normal levels of oxygen free radicals play an important role in cellular signal transduction, redox homeostasis, regulatory pathways, and metabolic processes. However, radiolysis of water induced by high-energy radiation can produce excessive amounts of exogenous oxygen free radicals, which cause severe oxidative damages to all cellular components, disrupt cellular structures and signaling pathways, and eventually lead to death. Herein, we show that hybrid nanoshields based on single-layer graphene encapsulating metal nanoparticles exhibit high catalytic activity in scavenging oxygen superoxide(center dot O-2(-)), hydroxyl (center dot OH), and hydroperoxyl (HO2 center dot) free radicals via electron transfer between the single-layer graphene and the metal core, thus achieving biocatalytic scavenging both in vitro and in vivo. The levels of the superoxide enzyme, DNA, and reactive oxygen species measured in vivo clearly show that the nanoshields can efficiently eliminate harmful oxygen free radicals at the cellular level, both in organs and circulating blood. Moreover, the nanoshieldslead to an increase in the overall survival rate of gamma ray-irradiated mice to up to 90%, showing the great potential of these systems as protective agentsagainst ionizing radiation.