evaluation of antibacterial and cytotoxic effects of k4 synthetic peptide

Introduction: with increasing antimicrobial resistance to common antibiotics, the development of alternative therapeutic strategies is necessary. also, an antibacterial peptide with numerous behavior and different properties such as net charge, hydrophobicity, length, etc. could act against pathogenic microorganisms. in recent years, novel peptides with activity against a wide range of bacteria have been introduced.methods: in this study, seventeen pathogenic bacteria were chosen to study the antibacterial effect of the k4 peptides using mic and mbc assays. the therapeutic index (ti) of this peptide was experimentally calculated by the ratio of hc50 to mic as a parameter to represent the specificity of amp. in silico analysis was performed to predict the physicochemical properties, structures, and behavior of this peptide. in vitro cytotoxic effect of the peptide was evaluated on the hela cell line using an mtt assay, and the amount of macrophage nitric oxide production was measured by the griess method on the j774 cell line.results: peptide concentrations of 25-400 µg/ml were seen as the mic value results for different bacteria. mbc assay showed such a result with a concentration of more than 25-400 µg/ml. the result of the hemolysis assay was 24 percent at a 1 mg/ml concentration. the amount of nitric oxide production in macrophage cell line j774 was 25.9873 µm at a 6.3 µg/ml peptide concentration. conclusions: k4 peptide had a strong antibacterial effect on some bacteria such as b. melitensis. this peptide may have a role in immunity to nitric oxide production. additionally, it enhances the bacterial killing mechanism of macrophages, making this peptide a potential agent against pathogens.