Synergistic effects of antimicrobial peptide dendrimer-chitosan polymer conjugates against Pseudomonas aeruginosa.

We report herein a new chemical platform for coupling chitosan derivatives to antimicrobial peptide dendrimers (AMPDs) with different degrees of ramification and molecular weights via thiol-maleimide reactions. Previous studies showed that simple incorporation of AMPDs to polymeric hydrogels resulted in a loss of antibacterial activity and augmented cytotoxicity to mammalian cells. We have shown that coupling AMPDs to chitosan derivatives enabled the two compounds to act synergistically. We showed that the antimicrobial activity was preserved when incorporating AMPD conjugates into various biopolymer formulations, including nanoparticles, gels, and foams. Investigating their mechanism of action using electron and time-lapse microscopy, we showed that the AMPD-chitosan conjugates were internalized after damaging outer and inner Gram-negative bacterial membranes. We also showed the absence of AMPD conjugates toxicity to mammalian cells. This chemical technological platform could be used for the development of new membrane disruptive therapeutics to eradicate pathogens present in acute and chronic wounds.