Poly(amino acid) is an important biomimetic material due to its unique biocompatibility and potential application in gene transfection

drug delivery

and prevention of viral infections.For example

ε-poly-lysine (ε-PL) is an uncommon cationic homopolymer produced by the fermentation process.Due to its significant antimicrobial activity and nontoxicity to humans

ε-PL is now industrially produced as an additive in food and cosmetics

biodegradable fibers

highly water absorbable hydrogels and drug carriers.However

due to the lack of appropriate polymerization method

ε-PL is now produced mainly by a fermentation process.The ε-PL with a molecular weight less than 4×103 is obtained by biosynthetic method and no copolymers composed of lysine and other amino acids can be found in the producer strains

probably because the two amino acids are polymerized by different enzymes.Consequently

the composition and properties of the resultant polymers are hard to regulate.Here

we report a new chemical strategy

based on ring-opening polymerization (ROP) of lactam

to obtain ε-PL with diverse molecular weight from renewable lysine monomer.Compared with ROP of lysine via the N-carboxyanhydride (NCA) intermediate

this new strategy for ε-PL

through ROP and without phosgene

allows for new opportunities in biomaterials applications.Moreover

this methodology may provide access to the production of γ-polyglutamate and β-poly(aspartic acid) from glutamic acid and aspartic acid monomers

respectively.