Surface Ligand Engineering Ruthenium Nanozyme Superior to Horseradish Peroxidase for Enhanced Immunoassay.

Nanozymes have great potential to be used as an alternative to natural enzymes in a variety of fields. However, low catalytic activity compared with natural enzymes limits their practical use. It is still challenging to design nanozymes comparable with their natural counterparts in terms of specific activity. In this study, a surface engineering strategy is employed to improve the specific activity of Ru nanozymes using charge-transferrable ligands such as polystyrene sulfonate (PSS). PSS modified Ru nanozyme exhibits a peroxidase (POD)-like specific activity of up to 2820 U mg -1 , which is twice that of horseradish peroxidase (HRP) (1305 U mg -1 ). Mechanism studies suggest that PSS readily accepts negative charge from Ru, thus reducing the affinity between Ru and ·OH. Importantly, the modified Ru-POD nanozyme is successfully used to develop an immunoassay for human alpha-fetoprotein (AFP) and achieves a 140-fold increase in detection sensitivity compared with traditional HRP-based ELISA. Therefore, this work provides a feasible route to design nanozyme with high specific activity that meets the practical use as an alternative to natural enzyme. This article is protected by copyright. All rights reserved.