Antibacterial Activity of M-MOF Nanomaterials (M = Fe, Co, Ni, Cu, and Zn): Impact of Metal Centers

Bacterial infections result in significant burdens on public health, especially with the increasing prevalence of antibiotic resistance owing to the overuse of antibiotics. The development of the next-generation nanoantibacterial materials as alternatives to antibiotics is urgently needed. Metal–organic frameworks (MOFs) have been emerging as promising antibacterial materials. However, the impact of metal centers on the properties and antibacterial activity of MOFs has not been clarified to date. In this work, five M-MOF nanomaterials (M = Fe, Co, Ni, Cu, Zn) are synthesized with 2-methylimidazole as an organic ligand. Subsequently, the minimum inhibitory concentration (MIC), minimum bactericidal concentration, and time-kill curves are studied to evaluate their antibacterial activity. In addition, the destruction of the bacterial cells after treatment with M-MOFs is observed via scanning electron microscopy. The experimental results demonstrate that the Co-MOF and Zn-MOF polyhedra exhibit optimal antibacterial activity. They can effectively inhibit the growth of both Gram-negative bacteria Escherichia coli and Gram-positive bacteria Staphylococcus aureus at a low concentration. On the other hand, the Fe-MOF irregular particles show the weakest antibacterial activity among five M-MOFs and the antibacterial activity of the Ni-MOF and Cu-MOF nanosheets are comparable to each other. The huge difference in antibacterial activity of M-MOFs is attributed to the difference in the shape and size, specific surface area, surface charge, ion release, and production of reactive oxygen species. Overall, this study clarifies the relationship between metal centers in M-MOFs and their antibacterial activity.