Highly efficient antibacterial diblock copolypeptides based on lysine and phenylalanine

A series of amphiphilic diblock copolypeptides (K-30-b-F-15, K-30-b-F-30, and K-30-b-F-45) were synthesized via N-carboxy-alpha-amino-anhydride ring-opening polymerization. The copolypeptides had excellent antibacterial efficacy to both Gram positive (S. aureus) and Gram negative (E. coli) bacteria. The minimum inhibitory concentrations (MICs) against E. coli and S. aureus are 8 mu gmL(-1) and 2 mu gmL(-1), respectively, lower than most natural and artificial antimicrobial peptides (AMPs). The morphological changes of the bacteria treated with diblock copolypeptides were investigated by transmission electron microscopy; the results proved that the diblock copolypeptides had a similar antibacterial pore-forming mechanism to natural cationic peptides. This was confirmed by laser scanning confocal microscope images. CCK-8 results and the MICs showed that the diblock copolypeptides have high selectivity to bacteria, which suggested that the diblock copolypeptides could be excellent candidates to replace traditional antibiotics in future.