Highly Potent Bactericidal Activity of Porous Metal-Organic Frameworks

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Recent outbreaks of bacterial infection leading to human fatalities have been a motivational force for us to develop antibacterial agents with high potency and long-term stability. A novel cobalt (Co) based metal-organic framework (MOF) was tested and shown to be highly effective at inactivating model microorganisms. Gram-negative bacteria,Escherichia coli(strains DH5alpha and XL1-Blue) were selected to determine the antibacterial activities of the Co MOF. In this MOF, the Co serves as a central element and an octa-topic carboxylate ligand, tetrakis [(3,5-dicarboxyphenyl)-oxamethyl] methane (TDM8−) serves as a bridging linker. X-ray crystallographic studies indicate that Co-TDM crystallizes in tetragonal space groupPSymbol21mwith a porous 3D framework.

The potency of the Co-TDM disinfectant was evaluated using a minimal bactericidal concentration (MBC) benchmark and was determined to be 10–15 ppm within a short incubation time period (<60 min). Compared with previous work using silver nanoparticles and silver-modified TiO2 nano- composites over the same time period, the MBC and effectiveness of Co-TDM are superior. Electron microscopy images indicate that the Co-TDM displayed distinctive grain boundaries and well-developed reticulates. The Co active sites rapidly catalyzed the lipid peroxidation, causing rupture of the bacterial membrane followed by inactivation, with 100% recycling and high persistence (>4 weeks). This MOF-based approach may lead to a new paradigm for MOF applications in diverse biological fields due to their inherent porous structure, tunable surface functional groups, and adjustable metal coordination environments.

A metal-organic framework, Co-TDM, composed of a unique octa-topic carboxylate ligand and bimeric μ2-H2O-centered basic carboxylate cluster is presented as a new bactericidal material. Electron microscopy analysis indicated the Co-TDM was highly crystalline, displaying distinctive grain boundaries and well-developed reticulates, which allow rapid, potent bacterial inactivation. Rupture of the bacterial membrane is the mechanism of cell death, as determined by EDS elemental mapping. A low MBC (10-15 ppm) and the rapid effectiveness of Co-TDM at inactivating the Gram-negative bacteriaEscherichia colidemonstrate a new avenue for MOFs in biomedical applications.

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