Ruthenium Complexes with 2-Pyridin-2-yl-1H-benzimidazole as Potential Antimicrobial Agents: Correlation between Chemical Properties and Anti-Biofilm Effects

Abstract

Antimicrobial resistance is a growing public health concern that requires urgent action. Biofilm-associated resistance to antimicrobials begins at the attachment phase and increases as the biofilms maturate. Hence, interrupting the initial binding process of bacteria to surfaces is essential to effectively prevent biofilm-associated problems. Herein, we have evaluated the antibacterial and anti-biofilm activities of three ruthenium complexes in different oxidation states with 2-pyridin-2-yl-1H-benzimidazole (L1 = 2,2′-PyBIm): [(η6-p-cymene)RuIIClL1]PF6 (Ru(II) complex), mer-[RuIIICl3(CH3CN)L1]·L1·3H2O (Ru(III) complex), (H2L1)2[RuIIICl4(CH3CN)2]2[RuIVCl4(CH3CN)2]·2Cl·6H2O (Ru(III/IV) complex). The biological activity of the compounds was screened against Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa strains. The results indicated that the anti-biofilm activity of the Ru complexes at concentration of 1 mM was better than that of the ligand alone against the P. aeruginosa PAO1. It means that ligand, in combination with ruthenium ion, shows a synergistic effect. The effect of the Ru complexes on cell surface properties was determined by the contact angle and zeta potential values. The electric and physical properties of the microbial surface are useful tools for the examined aggregation phenomenon and disruption of the adhesion. Considering that intermolecular interactions are important and largely define the functions of compounds, we examined interactions in the crystals of the Ru complexes using the Hirshfeld surface analysis.

Synthesis, Characterization and Biological Investigations of Half-Sandwich Ruthenium(II) Complexes Containing Benzimidazole Moiety

“…The possibility of using complexes that simultaneously limit the development of cancer cells and protect against bacterial infections would be a great solution. Of course, it should be emphasized that the described properties do not always go hand in hand, which is confirmed by our previous research [23][24][25][26][27]. The antibiofilm effect depends on many factors, such as the structure of the complex-the type of central ion, ligand, the presence of chloride ions or its properties.…”

Synthesis, Spectroscopic, and Biological Assessments on Some New Rare Earth Metal Adrenaline Adducts

“…Isolated colonies of each organism that might be detrimental were chosen from the main agar plates and their vulnerability was evaluated using the disc dispersion technique [18][19][20][21][22][23][24][25][26][27][28]. There are many research papers that deal with the disc dispersion technique in conducting the biological evaluation of the prepared chemical compounds, and the findings of these can be listed as follows: the use of Ruthenium complexes with 2-pyridin-2-yl-1H-benzimidazole as potential antimicrobial agents has been discussed according to the correlation between chemical properties and anti-biofilm effects [18]. The possibility of redesigning the nature of ruthenium flavonoid complexes with antitumor, antimicrobial and cardioprotective activities was studied [19].…”

Microbial Biofilms and Antibiofilm Agents 2.0

“…Recent literature points to metal complexes as promising leads for the development of effective antibiofilm agents due to their multi-target and complex mechanisms of actions [ 15 ]. Two articles of the collection deal with this topic: in the first one, the Authors evaluated the antibacterial and antibiofilm activity of three ruthenium (Ru) complexes in different oxidation states, with 2-Pyridin-2-yl-1 H-benzimidazole [ 5 ], in the second manganese(II) complexes with heteroaromatic ligands (i.e., alcohol, aldehyde, ketone, and carboxylic acid) were investigated [ 6 ]. Interestingly, the antibiofilm activity of Ru complexes was found to increase as compared to that of the ligand alone and was demonstrated to be possibly due to an effect on the hydrophobicity of the bacterial surface that, in turn, reduced the adhesive properties of the treated bacteria ( Pseudomonas aeruginosa PAO1) [ 5 ].…”

“…Two articles of the collection deal with this topic: in the first one, the Authors evaluated the antibacterial and antibiofilm activity of three ruthenium (Ru) complexes in different oxidation states, with 2-Pyridin-2-yl-1 H-benzimidazole [ 5 ], in the second manganese(II) complexes with heteroaromatic ligands (i.e., alcohol, aldehyde, ketone, and carboxylic acid) were investigated [ 6 ]. Interestingly, the antibiofilm activity of Ru complexes was found to increase as compared to that of the ligand alone and was demonstrated to be possibly due to an effect on the hydrophobicity of the bacterial surface that, in turn, reduced the adhesive properties of the treated bacteria ( Pseudomonas aeruginosa PAO1) [ 5 ]. In the case of manganese complexes, again, an increased activity against P. aeruginosa PAO1 biofilms was observed as compared to the free ligands or manganese(II) salts, together with morphological changes in the biofilm structure and reduction in the secretion of pyoverdine, one of the major virulence factor of P. aeruginosa [ 6 ].…”

“…In this context, the aim of this Special Issue was to gather a collection of papers focused on biofilm infections, and on the development of new antibiofilm agents to target them. A total of eight research articles and two reviews were collected disclosing new and interesting aspects on the physiology of bacterial biofilms [2], biofilm interaction with host cells [3], and innovative and promising approaches to prevent or eradicate microbial biofilms, not only in the medical setting [4][5][6][7][8][9][10] but also in the environment [11]. The contribution of Rahman et al [2] focuses on how the proteome of Staphylococcus aureus biofilms changes with aging compared with planktonic growth.…”