Antibacterial efficacy of copper-based metal–organic frameworks against Escherichia coli and Lactobacillus

Abstract

The widespread and excessive use of antimicrobial drugs has resulted in a concerning rise in bacterial resistance, leading to a risk of untreatable infections. The aim of this study was to formulate a robust and efficient antibacterial treatment to address this challenge. Previous work focused on the effectiveness of the Cu-BTC metal–organic framework (MOF; BTC stands for 1,3,5-benzenetricarboxylate) in combatting various bacterial strains. Herein, we compare the antibacterial properties of Cu-BTC with our newly designed Cu-GA MOF, consisting of copper ions bridged by deprotonated gallate ligands (H₂gal²⁻), against Escherichia coli (E. coli) and Lactobacillus bacteria. Cu-GA was synthesized hydrothermally from copper salt and naturally derived gallic acid (H₄gal) and characterized for antibacterial evaluation. The gradual breakdown of Cu(H₂gal) resulted in a significant antibacterial effect that is due to the release of copper ions and gallate ligands from the framework. Both copper MOFs were nontoxic to bacteria at low concentrations and growth was completely inhibited at high concentrations when treated with Cu-BTC (1500 μg for E. coli and 1700 μg for Lactobacillus) and Cu-GA (2000 μg for both bacterial strains). Furthermore, our agarose gel electrophoresis results indicate that both MOFs could disrupt bacterial cell membranes, hindering the synthesis of DNA. These findings confirm the antibacterial properties of Cu-BTC and the successful internalization of Cu²⁺ ions and gallic acid by bacteria from the Cu-GA MOF framework, suggesting the potential for a sustained and effective therapeutic approach against pathogenic microorganisms.