Study on the Immobilization of Horseradish Peroxidase on a Multi-Level Composite Carrier SiO₂@MnO₂@MAF-7

This study addresses the issues of poor stability and difficulty in recovery of free horseradish peroxidase (HRP) by developing a multi-level composite immobilized carrier that combines high loading capacity with long-term stability. The SiO₂@MnO₂@MAF-7 core-shell structured carrier was prepared via a solvothermal self-assembly method. Three immobilization strategies-adsorption, covalent cross-linking, and encapsulation-were systematically compared for their immobilization efficacy on HRP. The material structure was analyzed using techniques such as specific surface area analysis (BET), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) to characterize the material structure. Enzyme kinetic parameter determination experiments were conducted to systematically evaluate the performance advantages of the immobilized enzyme. BET analysis showed that SiO₂@MnO₂@MAF-7 had a specific surface area of 251.99 m²/g and a mesoporous area of 12.47 nm, and its HRP loading was 50.37 U/mg (immobilization efficiency 85.03%). Compared with free HRP, the Km value of the immobilized enzyme was decreased by 42%, the activity retention rate was increased by 35-50% at 80 °C and pH 4-9, and the activity was maintained by 65% after five repeated uses. In this study, MAF-7 was combined with MnO₂/SiO₂ for HRP immobilization for the first time, and the triple effect of rigid support-catalytic synergy-confined protection synergistically improved the stability of the enzyme, providing a new strategy for the industrial application of oxidoreductases.