Antimicrobial effect of polydopamine coating on Escherichia coli

Discovery of new antimicrobials is highly desired due to the emergence of microorganisms that have multi-drug resistant capability. The purpose of this study was to investigate the antimicrobial effect of dopamine (DA) on Escherichia coli. DA's inhibitory activity was tested at different initial E. coli cell concentrations. Significant 3.5 and 4.2 log inhibitions were observed for 1 × 108 and 1 × 107 cells per mL, when compared to controls, corresponding to 99.97 and 99.99% inhibitions. Microscopic techniques (optical, fluorescence, and scanning electron) and Fourier transform infrared spectroscopy confirmed a polydopamine coating on the bacterial cells. Capillary electrophoresis with ultra-violet detection indicated a significant change in the cell structure caused by a low dose (100 mg L−1) of DA within 200 min of incubation.