Many experimental and clinical data have demonstrated that antibiotic-resistance pathogens, such as Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), may play a vital role in priming chronic inflammation. There is thus a great need to develop novel antibacterial materials, and particularly those that are less likely to lead to bacterial resistance.

Now, in a paper appearing recently in Science Bulletin, a team of scientists at the National Center for Nanoscience and Technology, China, led by Guangjun Nie and Yuliang Zhao, has designed and synthesized bio-compatible and biodegradable ε-poly-lysine (EPL)/poly (ε-caprolactone) (PCL) nanoparticles (NPs), which have effective antibacterial activity and no significant cytotoxicity to mammalian cells.

Most clinically used antibiotics do not physically damage the cell membranes/walls, but rather target the cell wall and penetrate into the cell, inhibiting protein synthesis and DNA replication. As a result, bacterial morphology is preserved. Bacteria are increasingly growing resistant to conventional antibiotics. Biocompatible and biodegradable ε-poly-L-lysine (EPL)/poly (e-caprolactone) (PCL) copolymer was designed and synthesized. The amphiphilic EPL-PCL copolymer could easily self-assembled into mono-dispersed nanoparticles (NPs), which showed a broad-spectrum antibacterial activity against E. coli, S. aureus and Bacillus subtilis (B. subtilis).

The NPs have been found that they can disrupt bacterial walls/membranes and induce the increasing in reactive oxygen species and alkaline phosphatase levels. More importantly, the self-assembled NPs induced the changes in bacterial osmotic pressure, resulting in cell invagination to form holes and cause the leakage of cytoplasm.

Taken together, these results suggest that the EPL-PCL NPs can be further developed to be a promising antimicrobial agent to treat infectious diseases as surfactants and emulsifiers to enhance drug encapsulation efficiency and antimicrobial activity.

Citation: Ruifang Zhao, Hai Wang, Tianjiao Ji, Greg Anderson, Guangjun Nie, Yuliang Zhao. Biodegradable cationic ε-poly-L-lysine-conjugated polymeric nanoparticles as a new effective antibacterial agent. Science Bulletin, 2015, 60(2): 216-226. This work was supported by the National Basic Research Program of China (2012CB934000, 2011CB933400) and the National Natural Science Foundation of China (31325010, 21277037).