Facile synthesis of Cu-CuFe2O4 nanozymes for sensitive assay of H2O2 and GSH

Abstract

Artificial enzymes have drawn substantial research interest from the scientific community due to their advantages over natural enzymes. However, majority of artificial enzymes exhibit low affinity towards H₂O₂, which means that a high H₂O₂ concentration is needed for the oxidation of a substrate such as 3,3′,5,5′-tetramethylbenzidine (TMB) to blue-colored oxTMB. With this concern, Cu-CuFe₂O₄ was facilely synthesized, wherein, Cu⁰ accelerates the redox capacity of Cu-CuFe₂O₄ as well as the electron transfer between CuFe₂O₄ and H₂O₂. These materials induce excellent activity as a peroxidase. Cu-CuFe₂O₄ shows high affinity towards H₂O₂ with lower Michaelis–Menten constant (K_m) than the reported values for ferrites and Horseradish enzyme (HRP). Moreover, it took only 5 min to detect hydrogen peroxide (H₂O₂) and glutathione (GSH) through a colorimetric assay using Cu-CuFe₂O₄. Compared with CuFe₂O₄, the limit of detection (LOD) is about 90-fold lower for H₂O₂ using Cu-CuFe₂O₄. In addition, Cu-CuFe₂O₄ shows high stability as a nanozyme. Thus, the mechanism of the peroxidase-like nanozyme Cu-CuFe₂O₄ is proposed.