Improvement of the Antimicrobial Peptide Activity by Means of Chitosan-Based Nanoparticles

This study demonstrated the enhancement of the bioactivity of Cm-p1 and Lip1 antimicrobial peptides (AMPs) against Botrytis cinerea when included within chitosan nanoparticles (CS-NPs). The physicochemical properties of these AMPs and the adequacy of CS-NPs for their encapsulation were predicted by in silico studies. When the antimicrobial activities of the free peptides were analyzed, significant differences were found, but their encapsulation in CS-NPs significantly improved their efficacy in reducing conidia germination and hyphal growth against B. cinerea, resulting in a total inhibition of germination at concentrations greater than 800 µM (Cm-p1) or 6.25 µM (Lip1). Both AMPs were successfully encapsulated into 190-239 nm CS-NPs with encapsulation efficiencies (EE%) greater than 96%, when pH of CS solutions was increased to 4.7, and polydispersity indices below 0.329 by the ionic gelation method. Based on the experimental data obtained, the antimicrobial properties of CS are undoubtedly related to the enhancement of the activity of these AMPs when encapsulated into CS-NPs, although the use of a vector to deliver the AMPs to the cells must be the main cause of this effect. However, further studies are needed to demonstrate the penetration of these peptides through microbial membranes because of their transport within the CS-NPs.