Direct evidence for catalase and peroxidase activities of ferritin–platinum nanoparticles

Using apoferritin (apoFt) as a nucleation substrate, we have successfully synthesized 1–2 nm platinum nanoparticles (Pt–Ft) which are highly stable. By directly measuring the products of Pt–Ft-catalyzed reactions, we showed, with no doubt, Pt–Ft possesses both catalase and peroxidase activities. With hydrogen peroxide as substrate, we observed oxygen gas bubbles were generated from hydrogen peroxide decomposed by Pt–Ft; the generation of oxygen gas strongly supports Pt–Ft reacts as catalase, other than peroxidase. While with organic dyes and hydrogen peroxide as substrates, distinctive color products were formed catalyzed by Pt–Ft, which indicates a peroxidase-like activity. Interestingly, these biomimetic properties showed differential response to pH and temperature for different reaction substrates. Pt–Ft showed a significant increase in catalase activity with increasing pH and temperature. The HRP-like activity of Pt–Ft was optimal at physiological temperature and slightly acidic conditions. Our current study demonstrates that Pt–Ft possesses both catalase and peroxidase activities for different substrates under different conditions.