Fig. 1. Copolypeptide and hydrogels preparation and characterization. (A) Schematic illustration of the synthesis of poly(l-glutamic acid-co-l-lysine) peptide. (B) Representative GPC result indicates that the poly(l-glutamic acid-co-l-lysine) peptide has a molecular weight around 17.6 kDa with PDI equal to 1.57. (C) SEM images of lyophilized copolypeptide hydrogels with different crosslinking degrees (from top to bottom: 10%, 20% and 30%). The scale bars are 5 μm. (D) Statistics of the pore sizes of the copolypeptide hydrogels with different crosslinking degrees. *P value < 0.05 and ***P value < 0.001. (E) The summary of pore sizes and swelling ratios of copolypeptide hydrogels with different crosslinking degrees.