Can the interaction between the antimicrobial peptide LL-37 and alginate be exploited for the formulation of new biomaterials with antimicrobial properties?

In this study, we took advantage of the strong interaction between the antimicrobial peptide LL-37 and anionic polysaccharides, such as alginate, to design and evaluate a new biomaterial with putative antibacterial properties. To begin with, we have investigated the effect of different biocompatible polysaccharides on both the cytotoxicity and the antimicrobial activity of LL-37, a powerful endogenous antimicrobial peptide of human origin, whose use in therapy has been hampered by its toxicity to host cells. Interactions of the peptide with polysaccharides were evaluated by circular dichroism analyses, which revealed a different capacity of the polymers to induce the active helical conformation in the peptide. Among the polysaccharides tested, sodium alginate was the only one that significantly reduced the toxicity of LL-37 toward mammalian cells. A sodium alginate/LL-37 preparation was then tested on four bacterial strains. The Gram-negative bacteria resulted susceptible to the mixture, while the growth of the Gram-positive ones was poorly affected and only at the highest peptide concentration tested. Following the positive results with Gram-negative species, the alginate/LL-37 binary system was used for the preparation of calcium alginate beads, which were tested for peptide release.