Investigation of antibiofilm activity of ruthenium complex

In this study, the ruthenium complex containing bipyridine ligand (Ru(4,4'- dicarboxy-2,2'-bipyridine)(4,4'-bis(3-ethylheptyl)-2,2'-bipyridine)(NCS)2) was used targeting antibiofilm activity. The biofilm inhibition and disruption performance of RuCS27 was tested in vitro via the XTT reduction method against Pseudomonas aeruginosa PA01, Escherichia coli ATCC 8739, Listeria monocytogenes NCTC 11994, Staphylococcus aureus ATCC 25923, Enterococcus faecalis ATCC 19433, Listeria innocua (6a) ATCC 32090, Streptococcus parasanguinis ATCC 15909, Bacillus cereus ATCC 10976, and Enterococcus hirae ATCC 10541. 40 µM RuCS27 inhibited biofilm formation of P. aeruginosa, E. coli, S. aureus, and E. faecalis by 63.27%, 92.59%, 82.68%, and 95.44%, respectively, while 65 µM RuCS27 inhibited 43.71% of L. innocua and 43.15% of B. cereus biofilm formation. In contrast, no inhibition effect was observed against the biofilms of E. hirae and S. parasanguinis. In the biofilm disruption activity of RuCS27, the exposure time to ruthenium was found to be more important than the biofilm age. Bacterial biofilm structures were stained with propidium iodide and DAPI and examined under a fluorescence microscope. In both stains, a reduction in biofilm density was observed in bacteria treated with RuCS27 compared to the control. It was concluded that RuCS27 inhibited biofilm formation of the pathogens and reduced the density of pre- existing biofilms. According to these results, RuCS27 could be a promising antibiofilm agent to prevent and eliminate bacterial biofilms.