A Comparative Analysis of the Antibacterial Spectrum of Ultrasmall Manganese Ferrite Nanozymes with Varied Surface Modifications.

Bacterial infectious diseases pose a significant global challenge. However, conventional antibacterial agents exhibit limited therapeutic effectiveness due to the emergence of drug resistance, necessitating the exploration of novel antibacterial strategies. Nanozymes have emerged as a highly promising alternative to antibiotics, owing to their particular catalytic activities against pathogens. Herein, we synthesized ultrasmall-sized MnFe 2 O 4 nanozymes with different charges (MnFe 2 O 4 -COOH, MnFe 2 O 4 -PEG, MnFe 2 O 4 -NH 2 ) and assessed their antibacterial capabilities. It was found that MnFe 2 O 4 nanozymes exhibited both antibacterial and antibiofilm properties attributed to their excellent peroxidase-like activities and small sizes, enabling them to penetrate biofilms and interact with bacteria. Moreover, MnFe 2 O 4 nanozymes effectively expedite wound healing within 12 days and facilitate tissue repair and regeneration while concurrently reducing inflammation. MnFe 2 O 4 -COOH displayed favorable antibacterial activity against Gram-positive bacteria, with 80% bacterial removal efficiency against MRSA by interacting with phosphatidylglycerol (PG) and cardiolipin (CL) of the membrane. By interacting with negatively charged bacteria surfaces, MnFe 2 O 4 -NH 2 demonstrated the most significant and broad-spectrum antibacterial activity, with 95 and 85% removal efficiency against methicillin-resistant Staphylococcus aureus (MRSA) and P. aeruginosa , respectively. MnFe 2 O 4 -PEG dissipated membrane potential and reduced ATP levels in MRSA and P. aeruginosa , showing relatively broad-spectrum antibacterial activity. To conclude, MnFe 2 O 4 nanozymes offer a promising therapeutic approach for treating wound infections.