Casein-coated Fe3O4 nanozymes with enhanced peroxidase-like activity for synergistic doxorubicin delivery and catalytic anticancer therapy.

Cancer remains a complex and enduring challenge of the 21st century. Due to the limitations of current cancer treatments, the implementation of robust and innovative therapeutic strategies is crucial. The robust catalytic activity of nanozymes positions them as a strong contender to replace natural enzymes within the developing field of nanocatalytic medicine. This study investigates the peroxidase (POD)-like activity of casein-coated Fe3O4 nanozymes (Fe3O4@Cs) to augment the therapeutic effectiveness of the chemotherapeutic agent doxorubicin (DOX). The casein coating enhanced the POD-like activity of Fe3O4 nanoparticles by 91%, as evidenced by an increase in specific activity. Additionally, optimization studies revealed that the Fe3O4@Cs nanozymes exhibited optimal catalytic activity under acidic conditions and demonstrated excellent thermal stability. Kinetic analysis revealed that the catalytic activity of Fe3O4@Cs nanozymes followed Michaelis-Menten kinetics. Furthermore, casein coating significantly enhanced the catalytic activity of Fe3O4 by increasing the reaction vmax. The Fe3O4@Cs nanocarriers demonstrated a substantial drug loading capacity, with approximately 755 µg DOX per milligram of nanoparticle, highlighting their potential as an efficient drug delivery system. Mechanistically, the synergistic interaction between controlled DOX release and the nanozymes' inherent catalytic activity, driving reactive oxygen species (ROS) production via the Fenton reaction, led to a significant increase in cytotoxic efficacy against human breast adenocarcinoma MCF-7 cells. This dual mechanism significantly enhanced the therapeutic anticancer effects of the nanobiocatalyst.