Low toxicity of metal-organic framework MOF-199 to bacteria Escherichia coli and Staphylococcus aureus

Abstract Metal-organic framework (MOF) materials are emerging materials for various applications because of their unique structures and properties. The hazards and environmental safety of MOF should be carefully evaluated before their large-scale production. Herein, we studied the toxicity and its mechanisms of MOF-199 to Gram-negative bacterium (Escherichia coli) and Gram-positive bacterium (Staphylococcus aureus). MOF-199 was synthesized from Cu(NO3)2 and 1,3,5-benzenetricarboxylic acid by hydrothermal method and well characterized before toxicological evaluations. MOF-199 was nontoxic to bacteria at low concentrations, and the bacterium growths were completely inhibited at high concentrations (900 mg/L for E. coli; 1200 mg/L for S. aureus). Cell deaths occurred at high MOF-199 concentrations associated with the loss of cytoplasm and flagella. The toxicological mechanisms of MOF-199 were attributed to oxidative stress, which further led to the membrane damage and DNA damage. The chemical origin of MOF-199 toxicity should be partially attributed to the released Cu2+ in culture medium, because Cu(NO3)2 was much more toxic than 1,3,5-benzenetricarboxylic acid. Our results indicated that MOF-199 was of low toxicity and environmental risks to bacteria.