Preparation and catalytic performance of a dual-enzyme activity nanozyme

Objective  To prepare a nanozyme with dual-enzyme activity and investigate the catalytic performance.

Methods  An iron-based metal-organic framework MIL-100 was synthesized via hydrothermal method. Subsequently, MIL-100 was mixed with aqua solution of chloroauric acid (HAuCl₄) under ice bath condition, where ultra-small gold nanoparticles (Au NPs) were grown in situ on its surface through freshly prepared sodium borohydride (NaBH₄) reduction to obtain a dual-enzyme activity nanozyme Au NPs@MIL-100 composite. Transmission electron microscopy (TEM), ultraviolet-visible spectrophotometry (UV-vis), fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS) and X-ray photoelectron spectrometer (XPS) were used for characterizing the nanozyme. Furthermore, the catalytic performance of nanozyme was evaluated by UV-vis spectroscopy and the capacity of the nanozyme to generate reactive oxygen species (ROS) in cells was observed using confocal laser scanning microscopy (CLSM).

Results  The synthesized Au NPs@MIL-100 nanozyme had a particle size of approximately 70 nm, with the surface-attached Au NPs size less than 5 nm. Moreover, MIL-100 demonstrated peroxidase-like (POD) activity by catalyzing hydrogen peroxide (H₂O₂) to generate hydroxyl radicals (·OH), showing time-dependent catalytic effects and reaching a steady state at 20 min; while the Au NPs exhibited glucose oxidase-like (GOx) activity by catalyzing the oxidation of glucose to produce H₂O₂, similarly showing time-dependent catalytic effects. The dual-enzyme nanozyme Au NPs@MIL-100 could efficiently generate ROS in triple-negative breast cancer (4T1) cells.

Conclusion  The dual-enzyme activity nanozyme Au NPs@MIL-100 was successfully prepared. Au NPs@MIL-100, with both POD-like and GOx-like activities, can enhance the level of ROS in 4T1 cells, which offers a new strategy for the development of tumor starvation therapy nanocarrier systems.