Conjugation of CRAMP18-35 Peptide to Chitosan and Hydroxypropyl Chitosan via Copper-Catalyzed Azide-Alkyne Cycloaddition and Investigation of Antibacterial Activity

Int J Mol Sci. 2024 Aug 30;25(17):9440. doi: 10.3390/ijms25179440.

Abstract

We developed a synthesis strategy involving a diazo transfer reaction and subsequent click reaction to conjugate a murine cathelicidin-related antimicrobial peptide (CRAMP18-35) to chitosan and hydroxypropyl chitosan (HPC), confirmed the structure, and investigated the antimicrobial activity. Chitosan azide and HPC-azide were prepared with a low degree of azidation by reacting the parent chitosan and HPC with imidazole sulfonyl azide hydrochloride. CRAMP18-35 carrying an N-terminal pentynoyl group was successfully grafted onto chitosan and HPC via copper-catalyzed azide-alkyne cycloaddition (CuAAC) reaction. The chitosan-peptide conjugates were characterized by IR spectroscopy and proton NMR to confirm the conversion of the azide to 1,2,3-triazole and to determine the degree of substitution (DS). The DS of the chitosan and HPC CRAMP18-35 conjugates was 0.20 and 0.13, respectively. The antibacterial activity of chitosan-peptide conjugates was evaluated for activity against two species of Gram-positive bacteria, Staphylococcus aureus (S. aureus) and Enterococcus faecalis (E. faecalis), and two species of Gram-negative bacteria, Escherichia coli (E. coli) and Pseudomonas aeruginosa (P. aeruginosa). The antimicrobial peptide conjugates were selectively active against the Gram-negative bacteria and lacking activity against Gram-positive bacteria.

Keywords: antibacterial activity; antimicrobial peptide; chitosan; click chemistry.

MeSH terms

  • Alkynes* / chemistry
  • Animals
  • Anti-Bacterial Agents* / chemical synthesis
  • Anti-Bacterial Agents* / chemistry
  • Anti-Bacterial Agents* / pharmacology
  • Antimicrobial Cationic Peptides / chemistry
  • Antimicrobial Cationic Peptides / pharmacology
  • Azides* / chemistry
  • Catalysis
  • Cathelicidins
  • Chitosan* / analogs & derivatives
  • Chitosan* / chemistry
  • Chitosan* / pharmacology
  • Copper* / chemistry
  • Cycloaddition Reaction*
  • Enterococcus faecalis / drug effects
  • Enterococcus faecalis / growth & development
  • Mice
  • Microbial Sensitivity Tests*
  • Staphylococcus aureus / drug effects

Substances

  • Chitosan
  • Anti-Bacterial Agents
  • Copper
  • Azides
  • Alkynes
  • Antimicrobial Cationic Peptides
  • Cathelicidins