2, School of Science of Tianjin University, Tianjin, , China
FePd magnetic nanoparticles (NPs) were developed as artificial enzymes with high biocompatibility and reusability, named ‘magnetozymes’, in a one-pot aqueous synthesis method using glutathione (GSH) and cysteine (Cys) as surfactants. The prepared hydrophilic FePd magnetozymes can be successfully re-dispersed in water and have high zeta potentials of 21.8 and 29.5 mV for Cys- and GSH-stabilized magnetozymes, respectively. The saturation magnetizations of the Cys- and GSH-conjugated magnetozymes, measured by a superconducting quantum interference device, are 4.7 and 41.4 emu g−1, with both magnetozymes exhibiting superparamagnetism at 300 K. The catalytic activities were tested by measuring the reduction of fluorescent dye and hydrogen peroxide by optical absorption measurements and electrochemical characterization. The Cys-FePd and GSH-FePd NCs exhibited significantly enhanced efficiency, with catalytic constants more than 2- and 7- fold higher than horseradish peroxidase (HRP), respectively. The computational simulation and electrochemical analysis explain its enhancement of the catalytic effect that is resulted by fct-structure of FePd NCs as well as molecules surrounding NC surface. Furthermore, in vitro experiments reveal that the FePd NPs clearly behave like peroxidase to reduce ROS levels in mammalian cells. The cytotoxicity was analyzed by exposing the FePd magnetozymes to different cell lines for seven days, and they showed >90% viability at concentrations up to 20 μg mL–1. The FePd magnetozymes, having high saturation magnetizations and biocompatibility, enable a variety of possible catalytic and biological applications such as recyclable peroxidase-mimicking enzymes, antioxidant agents, and biosensors.