Peculiarities of Redox Catalysis With Peroxidase-Like Nanozymes.

Catalytic pathways of peroxidase-like nanozymes based on different nanomaterials are critically compared. For all nanomaterials, the catalytic rate constant (kcat) for reducing substrate is increased as the redox potential of the nanozyme itself is increased: 100 mV rise in the catalyst's redox potential provides 1000 times higher kcat. Logarithm of the catalytic constant as a function of both nanozyme and substrate redox potentials for Prussian Blue belongs to the same trend as for the enzyme peroxidase, whereas other materials (Fe3O4, CeO2, and LiFePO4) display significantly lower activity. Size-dependence of catalytic constant returns the slope from 2.6 to 2.8 in double logarithmic plots, indicating penetration of hydrogen peroxide to the bulk of nanozymes. The electrochemical rate constant, on the contrary, is much higher for smaller nanozymes, pointing to more dense packing of the electrocatalytic layer. Catalytically synthesized Prussian Blue nanozymes are successfully applied for ROS scavenging in living cells.