The Most Active Oxidase‐Mimicking Mn 2 O 3 Nanozyme for Biosensor Signal Generation

Abstract Oxidase‐mimicking nanozymes are more desirable than peroxidase‐mimicking ones since H 2 O 2 can be omitted. However, only a few nanomaterials are known for oxidase‐like activities. In this work, we compared the activity of Mn 2 O 3 , Mn 3 O 4 and MnO 2 and found that Mn 2 O 3 had the highest oxidase activity. Interestingly, the activity of Mn 2 O 3 was even inhibited by H 2 O 2 . The oxidase‐like activity of Mn 2 O 3 was not much affected by the presence of proteins such as bovine serum albumin (BSA), but the physisorption of antibodies to Mn 2 O 3 was not strong enough to withstand the displacement by BSA. We then treated Mn 2 O 3 with 3‐aminopropyltriethoxysilane to graft an amine group, which was used to conjugate antibodies using glutaraldehyde as a crosslinker. A one‐step indirect competitive ELISA (icELISA) was developed for the detection of isocarbophos, and an IC 50 of 261.7 ng/mL was obtained, comparable with the results of the standard two‐step assay using horseradish peroxidase (HRP)‐labeled antibodies. This assay has the advantage of significant timesaving for rapid detection of large amounts of samples. This work has discovered a highly efficient oxidase‐mimicking nanozyme useful for various nano‐ and analytical applications.