Reference material of Prussian blue nanozymes for their peroxidase-like activity

Nanozymes with wide applications have rapidly attracted tremendous attention from various fields in the last decade. However, research on the standardization of nanozymes is still lacking. Currently, the accurate evaluation and effective tracing of the enzyme-like activity of nanozymes have become a common concern. This work aims to develop a certified reference material (CRM) of Prussian blue nanozymes (PBNEs) for their peroxidase (POD)-like activity. The homogeneity and stability studies demonstrated that the property value of POD-like activity is consistent across different packing units, and remains unchanged during the one-year validity period of storage in the dark at 4 °C. The certified value of the POD-like activity of the PBNE CRM is assigned as 174 ± 13 U mg^-1 (k = 2) by interlaboratory comparison studies and traceable uncertain evaluation. Furthermore, the need for quality control of the POD-like activity of nanozymes was exemplified by comparing the influence of two additional PBNEs on the dry and wet chemical detection of glucose (Glu). As the first quality assurance tool of nanozymes, the PBNE CRM is expected to replace natural horse radish peroxidase (HRP) as an effective benchmark for assessing the analytical method and laboratory competence. In addition, this work also inspires the further standardization of nanozymes.