Augmenting nisin antibacterial activity: in-vitro analysis with 1-alkyl-1-methylpyrrolidin-1-ium bromide

Building on our earlier research, this study explores the improvement of the antibacterial activity of nisin (NIS) in the presence of long-range pyrrolidinium-based ionic liquids with Br⁻ counter ions, similar to those previously reported with NTF₂⁻. Our results demonstrate a notable enhancement in the antibacterial activity of NIS with ILs containing Br⁻ ions against Escherichia coli (E. coli), highlighting a discovery of their synergistic effects as NIS alone is found to be ineffective against E. coli. Additionally, a similar experiment against Staphylococcus aureus (S. aureus) showed increased efficacy of NIS in the presence of ILs. Flow cytometry and confocal microscopy analyses revealed that NIS-IL conjugates disrupt the membranes of both E. coli and S. aureus. We also performed an in-depth analysis of the complex formation between ILs and NIS using molecular docking, surface tension measurements, UV–vis spectroscopy, and dynamic light scattering, confirming strong interactions between the components. Furthermore, CD spectroscopy confirmed the stability of the complex, and hemocompatibility assays verified its compatibility with human serum albumin.

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