To determine the antibacterial action of complexes 1 and 2 on planktonic cells of bacteria, the broth microdilution method was used, with streptomycin as the reference antibiotic. intermolecular classical and rare weak hydrogen bonds, and stacking interactions significantly contribute to structure stabilization, leading to the formation of a supramolecular assembly. The microbiological tests have shown complex 1 exhibited a slightly higher anti-biofilm activity than that of compound 2. Interestingly, electrochemical studies have allowed us to determine the relationship between the oxidizing properties of complexes and their biological activity. Probably the mechanism of action of 1 1 and 2 is associated with generating a cellular response similar to oxidative stress in bacterial cells. infections are involved in several human diseases such as cystic fibrosis, meningitis, and septicaemia. The severe infections caused by this strain contribute to high mortality rates, mostly in hospitalized patients [2,3,4,5]. It is worth noting that antibiotic resistance and thus failures in the treatment of infections are mainly related to the mechanism of pathogenicity of microorganisms, which is the ability to form Rabbit polyclonal to CDC25C biofilms [6,7,8,9]. Generally, it is estimated that approximately 80% of all bacterial infections are associated with biofilm formation [6]. The structure of biofilms makes the bacterial cells that build them nearly 1000 times less sensitive to toxic substances (antibiotics, surfactants, and disinfectants) than their planktonic counterparts [7,8]. Moreover, conventional antibiotic therapy is able to eliminate only planktonic cells [7,8]. Studies on improving the treatment of bacterial biofilm infections are still currently being developed. In recent years, there has been an increased interest in the use of coordination complexes of transition metals such as silver, copper, gallium, zinc, cobalt, nickel, and ruthenium as anti-biofilm agents [10,11,12,13,14,15]. In our previous studies, we have reported evaluation results of the anti-biofilm activity of the obtained ruthenium complexes in different oxidation states. To the best of our knowledge, no previous research on the anti-biofilm activity of high-valent ruthenium complexes against has been investigated. So far, our studies have focused on ruthenium complexes that contain heterocyclic alcohols and carboxylic acids andpossess moderate anti-biofilm activity. Among the tested compounds, the best activity was observed for the chloride Ru(IV) complex in which the protonated ligand acted as a counter ion [16]. Weaker activity was determined for the ruthenium complexes in the +III and +IV oxidation states with N,O-donor ligands [17]. In this study, we have extended the scope of our research, N-Acetylglucosamine and some efforts have been made to modify the composition of the complexes. These modifications were intended to increase the biological activity of the compounds by introducing heterocyclic alcohols and carboxylic acids in protonated form. Also, Keppler and colleagues have observed significant biological activity of chloride ruthenium complexes (KP1019, NAMI-A) [18,19]. We used 2-hydroxymethylbenzimidazole (L1) and 3-hydroxy-2-quinoxalinecarboxylic acid (L12 commercial) containing privileged structures to achieve this effect. Accordingly, the aim of this work was to investigate the possibility of utilizing Ru(IV) complexes as effective inhibitors for bacterial biofilms of PAO1 (laboratory strain) and LES B58 (clinical strain). This choice resulted from the fact that was classified as critical, multi-resistant strain. The commonly used ATCC 8739 and ATCC 6538P were also tested. In this paper, we studied the following aspects: (1) to carry out the syntheses of new chloride Ru(IV) complexes and describe their crystal structures and physical-chemical properties; (2) to investigate of N-Acetylglucosamine the interactions between molecules in crystals; (3) to study the redox properties of the Ru(IV) complexes (by CV and DPV methods); (4) to gain information on the inhibition of bacterial growth and biofilm formation in the tested strains caused by ruthenium complexes; (5) to investigate oxidative DNA damage using the formamidopyrimidine-DNA glycosylase (Fpg); (6) to evaluate the regularity between electrochemical properties and biological activity. 2. Results and Discussion 2.1. Syntheses and Characterization Our previous studies have indicated the best activity was observed N-Acetylglucosamine for the chloride Ru(IV) complex in which the protonated ligand acted as a counter ion [16]. Thus, in this paper, complexes 1 and 2 were formed by reacting mother solution ([RuCl6]2?/[RuCl6]3?) [20] with the N,O-donor ligands (L1 and L12) in the presence of an EtOH/CH3CN/HCl mixture. The L1 molecules present in the solution are protonated (in the presence of HCl), and as a result, one of the coordination sites in the N,O-donor ligand is blocked. As a consequence, we obtained that hexachloride ruthenate(IV) N-Acetylglucosamine is balanced by organic counter-ions formed (HL1) (complex 1, Scheme 1A) and two protonated ligands in comparison to our previous experimental results [20]. Additionally, under the low-temperature conditions of crystallization, we observed the existence of ethanol in the crystal space, which acted as a solvent. The obtained red crystals of complex 1 are stable in air (m. chains formed by the C-HCl hydrogen bonds; (B) a view of a channel filled with L32, with marked Ru-Cl interactions and stacking interactions (Cg(1): 6-membered ring defined.
