Structure-antimicrobial activity relationship and action mechanism of dimeric quaternary ammonium amphiphiles

The antibacterial activity of the five dimeric quaternary ammonium amphiphiles against Escherichia coli were evaluated by determining the minimum inhibitory concentration (MIC) and compared with one monomeric quaternary ammonium amphiphile. The antibacterial activity of dimeric amphiphiles is superior to the corresponding monomeric amphiphile. The action mechanism was investigated by measuring the activity of β-galactosidase from E. coli and scanning electron microscopy (SEM) imaging of E. coli cells. The result of β-galactosidase activity shows that 12-8-12 disrupts the membrane of E.coli leading to the releasing of intracellular contents and death of bacterial cells. This conclusion was supported by scanning electron microscopy, which imaged the holes on the cell membrane and irregular shape of cells caused by treatment of 12-8-12.