A series of amphiphilic diblock copolypeptides (K -b-F , K -b-F , and K -b-F ) were synthesized via N-carboxy-α-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 μg mL and 2 μg mL , 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.

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A novel biodegradable and noncytotoxic polycaprolactone-polyethyleneglycol-3-poly(L-lysine) (PCL-PEG-EPL) triblock copolymer was synthesized via the combination of ring-opening polymerization and facile coupling reactions. The triblock copolymer can self-assemble into vesicles in aqueous solution, and PCL forms the vesicle membrane, whereas the PEG and EPL blocks constitute the vesicle coronas. Atomic force microscopy (AFM) and transmission electron microscopy (TEM) had proved its vesicular structure.The excellent antibacterial ability of the 3-poly(L-lysine) makes the vesicles have good antibacterial activities towards both E. coli (Gram negative) and S. aureus (Gram positive), and the minimal inhibitory concentrations (MICs) were both 62.5 mg mL À1