Hypothesis: Here, FePd magnetic nanoparticles (MNPs) are developed as artificial enzymes with high biocompatibility and reusability. Experiment: The nanoparticles (NPs) are synthesized in an aqueous solvent by one-pot synthesis utilizing glutathione (GSH) and cysteine (Cys) as surfactants. Findings: The prepared hydrophilic FePd NPs are redispersible in water. Further, they exhibit catalytic activity for the degradation of rhodamine B (RhB), as well as for the inhibition of reactive oxygen species (ROS) production induced by H2O2, which are two- and seven-fold enhancements of their catalytic performances, respectively, compared with that of horseradish peroxidase. The computational simulation and electrochemical analysis indicate that the enhancement of the catalytic effect is due to the protection of the MNP surface by GSH and Cys. In vitro experiments reveal that FePd MNPs behave like a peroxidase and decrease the ROS in mammalian cells. The cytotoxicity assessment of FePd MNPs via exposures to different cell lines for over seven days indicates that they can maintain the cell viability of >90% for up to 20 mu gmL(-1) concentration. FePd MNPs with high saturation magnetization and biocompatibility can be utilized as recyclable peroxidase-mimicking nanozymes and biosensors in a variety of catalytic and biological applications. (C) 2020 Elsevier Inc. All rights reserved.