The Most Active Oxidase-Mimicking Mn2O3 Nanozyme for Biosensor Signal Generation

Oxidase-mimicking nanozymes are more desirable than peroxidase-mimicking ones since H2O2 can be omitted. However, only a few nanomaterials are known for oxidase-like activities. In this work, we compared the activity of Mn2O3, Mn3O4 and MnO2 and found that Mn2O3 had the highest oxidase activity. Interestingly, the activity of Mn2O3 was even inhibited by H2O2. The oxidase-like activity of Mn2O3 was not much affected by the presence of proteins such as bovine serum albumin (BSA), but the physisorption of antibodies to Mn2O3 was not strong enough to withstand the displacement by BSA. We then treated Mn2O3 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 IC50 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.

Automated summary

This study identified that the oxidase-mimicking nanozyme Mn2O3 exhibits high efficiency and can be utilized for various nano- and analytical applications. A one-step indirect competitive ELISA assay was developed through modification for detection purposes.