Design and Synthesis of Bimetallic Cu(II) Compounds as Potent Antibacterial and Antibiofilm Agents with Metallo-β-Lactamase Inhibitory Activity Against Multidrug Resistant Pseudomonas aeruginosa

Abstract

In this research, a novel class of biologically active bimetallic Cu(II) compounds has been discovered as cutting-edge antibiofilm agents with metallo-β-lactamase (MBL) inhibitory activity against the clinically isolated multidrug-resistant (MDR) gram-negative bacterium, Pseudomonas aeruginosa (Pa-CI-1). As the traditional strategies for antibiotic development are proving inadequate against the swift evolution of bacterial resistance, there is an urgent need to establish novel antibacterial strategies with mechanism different from those of prevailing antibiotics. Thus, the 2,6-bis[N-{N-(carboxymethyl)-N-(pyridylmethyl)amine}methyl]-4-methylphenol (H₃L)-incorporated three bimetallic Cu(II) compounds, [Cu₂L(H₂O)(Cl)]·H₂O (1), [Cu₂L(H₂O)(NO₃)]·H₂O (2) and [Cu₂L(H₂O)(CH₃CO₂)]·H₂O (3) has been strategically designed and synthesized with an unsymmetrical coordination arrangement that synergistically modifies the electronic environment of Cu centers for the enhancement of antibacterial and antibiofilm activity. The electronic environment of Cu(II) and its adjoining atoms has been further modified by substituting Cl^- in 1 by NO₃ ^- in 2 and CH₃CO₂ ^- in 3. The standard nitrocefin assay disclosed that 1-3 significantly inhibited the activity of MBLs produced by Pa-CI-1 at the half minimum inhibitory concentration (1/2 MIC). Molecular docking study suggested an excellent propensity of these Cu compounds for binding with MBL-producing proteins such as Verona integron-encoded metallo-β-lactamase (VIM-1), Sao Paulo metallo-β-lactamase (SPM-1), imipenemase (IMP-1), AmpC, and New Delhi metallo-β-lactamase (NDM-1). However, the best possible interaction was observed for VIM-1 protein. All three Cu(II) compounds displayed significantly high antibacterial and antibiofilm activity as established by multiple bioassays, including ex vivo applicability studies. However, 1 and 3 showed an outstanding activity with MIC values of 200 and 150 µg/mL, respectively, in comparison to 2 with an MIC of 300 µg/mL. They showed an exceptional combinatorial activity when examined with five different commercially accessible β-lactam-based antibiotics, such as amoxicillin (AMX), chloramphenicol (CHL), cefotaxime (CTX), ceftriaxone (CTR), and cefoxitin (CX) against Pa-CI-1. It has been suggested that the as-synthesized Cu compounds also blocked the activity of MBLs via strong interactions with the active sites of enzymes, thus restoring the normal activity of the antibiotics. Our study disclosed that 1-3 could be the emergent drug leads and attract great attention to the materials and biological chemists, combating antimicrobial resistance (AMR).

Keywords: Ex vivo application potential; bimetallic Cu(II) compound; biofilm infection and multidrug resistance; clinically isolated Pseudomonas aeruginosa; metallo‐β‐lactamase inhibition; pyridine‐and carboxylate‐based organic scaffold.