Synthesis and bioactivity of pH-response chemically modified antimicrobial peptide hydrogels

In this study, peptides with antimicrobial activity and specific pH-response gel properties were designed and synthesized by introducing phenylalanine into transactivating transcriptor peptide TAT (YGRKKRRQRRR). In order to investigate the antibacterial mechanism, the interactions of TAT and its analogs with DNA were studied using multiple methods. Antimicrobial results indicated that a lower content of phenylalanine is associated with better antimicrobial effects. The synthesized peptides can form hydrogels and maintain their antimicrobial activity under high pH value condition. Rheological experiments revealed that an increase in phenylalanine enhances the gel-forming properties of peptides. Results of circular dichroism spectroscopy suggest that this may be due to an increase on alpha-helical structure with increasing of phenylalanine. TEM results clearly demonstrate the different structures of the peptide under different pH conditions. It forms fibers or network structures under high pH value instead of nanoparticles under low pH value. Drug release experiments showed that the peptide hydrogels had different release effects in different pH environments, demonstrating their potential application as drug carriers.