Nanomaterials for Selective Superoxide Dismutation

Abstract

Superoxide is a primary reactive oxygen species (ROS) formed from aerobic metabolism. Superoxide dismutase (SOD), by catalyzing the conversion of superoxide to form hydrogen peroxide and molecular oxygen, is a first-line defense against superoxide toxicity. Due to the protein nature of endogenous SOD, small molecule SOD mimetics are commonly used to protect against superoxide-mediated pathophysiological processes and identify the causal role of this ROS in diseases pathogenesis. Existing small molecule SOD mimetics, however, also are reactive toward other ROS and related species, including hydrogen peroxide, nitric oxide, and peroxynitrite, which makes it difficult to delineate the involvement of superoxide in the disease process. Nanomaterials, such as cerium oxide nanoparticles and fullerenes, also possess SOD activity, but again lack specificity for superoxide. A recent study by Samuel et al. reported in the Proceedings of the National Academy of Sciences of the United States of America (2015 Feb 24; 112(8):2343–8. doi: 10.1073/pnas.1417047112) demonstrates that poly(ethylene glycolated) hydrophilic carbon clusters (PEG-HCCs) efficiently catalyze the conversion of superoxide to form hydrogen peroxide and molecular oxygen, and more importantly, the carbon nanaoparticles are inert to nitric oxide and peroxynitrite. This work represents a major advancement in the development of SOD biomimetics that are highly specific for superoxide. Application of such specific SOD biomimetics would have significant impact on the field of superoxide biology and medicine.