Ammonia gas induced interfacial reconstruction of Cu/Zn-MOFs enhances SOD-like catalysis for intracellular ROS regulation and osteoimmunomodulation.

Developing nanozymes with high catalytic activity at low concentrations while mimicking the function of superoxide dismutase (SOD) remains a challenge. Inspired by the structure of Cu/Zn-SOD in the human body, we construct Cu/Zn-MOFs using 2-methylimidazole assembly, aiming to replicate the structure and catalytic properties of natural SOD. More importantly, we introduce an ammonia-assisted interfacial modulation strategy. After just 120 seconds of NH3 exposure, the zeta potential increased from +6.8 ± 2.0 mV to +14.4 ± 1.2 mV, and the oxidation state of the central metal atoms decreased, which resulted in a 2-fold increase in SOD-like activity. The modified Cu/Zn-MOF exhibited >60% superoxide radical scavenging efficiency at a low concentration of 800 ng mL-1, demonstrating competitive performance compared to previous MOF-based SOD mimetics. Additionally, this nanozyme efficiently scavenges intracellular reactive oxygen species (ROS), regulates macrophage polarization, and promotes osteoimmunomodulation, suggesting its potential for application in bone regeneration and oxidative stress-related therapeutic strategies.