Quantifying the Active Sites on Single Redox Active Nanoparticle

Superoxide dismutases (SODs) are metalloenzymes which actively participate in cellular defense against oxidative stress mediated damage. SOD is a naturally existing enzyme in our body which scavenges the superoxide radical (O2−.) to form oxygen and hydrogen peroxide. The enzyme goes through an electrochemical single electron transfer process and contains only one active site per molecule. Cerium oxide nanoparticles (CNPs) are versatile nano-constructs which have the ability to switch in and out of 3+ and 4+ oxidation states exhibiting redox nature. This alteration of oxidation states leading to electrochemical reactions allows CNPs to mimic SOD enzyme and act as efficient antioxidants owing to multiple active sites for scavenging superoxide radicals. CNPs have been established owing to their unique regenerative antioxidant property and tested in vivo and in vitro in different areas of biotechnology and medicine involving excessive oxidative stress disorders. The simultaneous presence of two different oxidation states on the surface of CNPs gives rise to oxygen vacancies which act as hot spots for catalytic reactions. Understanding the antioxidant efficiency of CNPs is one of the crucial issues concerning its dosage. In this study we shall compare the efficacy of different single nanoparticles with different surface chemistry. The enzymatic kinetics are keenly studied to quantify the SOD mimetic efficiency in terms of electrochemical rate constants and turnover numbers as compared to the natural SOD. This study assist in proficient selection of nanoparticles for oxidative stress disorders.