Antimicrobial peptides-loaded PLGA nanoparticles: Unravelling distinct release profiles and effect against Pseudomonas aeruginosa

Abstract

The encapsulation of antimicrobial peptides (AMPs) into nanoparticles (NPs) has been proposed as a strategy to mitigate their rapid degradation in vivo, a key barrier for their clinical translation. However, the efficacy of the AMP-NP systems depends on both the type of NP used and the AMP characteristics. This work aims to explore the encapsulation efficiency (EE), release profile, and antimicrobial performance of three different AMPs - Dhvar5 (LLLFLLKKRKKRKY; 14 aa; +8; 43 % hydrophobic), MSI78 (GIGKFLKKAKKFGKAFVKILKK; 22 aa; +9; 45 % hydrophobic), and LL37 (LLGDFFRKSKEKIGKEFKRIVQRIKDFLRNLVPRTES; 37 aa; +6; 38 % hydrophobic) - loaded into poly (lactic-co-glycolic acid) nanoparticles (PLGA NPs). Their minimal bactericidal concentration (MBC) against Pseudomonas aeruginosa, an opportunistic bacterium commonly involved in clinically persistent infections, was 64 μg/mL (Dhvar5), 1–4 μg/mL (MSI-78) and 32–64 μg/mL (LL37). According to I-TASSER prediction, all the AMPs used adopt an alpha-helical conformation. The EE% increased with AMP size: 50 %, 80 % and 88 % for Dhvar5, MSI78 and LL37, respectively. AMP release after 72h of stirring at 37 °C was higher for MSI78 (60 μg/mL, 46 %), followed by Dhvar5 (44 μg/mL, 60 %). Almost no release was observed for LL37 (8 μg/mL, 6 %). Complete eradication of P. aeruginosa was achieved for both Dhvar5 and MSI78 at 4 μg/mL in phosphate buffer saline (2h). A 2-log reduction was only found for MSI78 (32 μg/mL) in Muller Hinton Broth (2h), with no cytotoxic effects towards HFF-1 human fibroblasts. Overall, these findings suggest that MSI78-NPs was the most promising formulation, combining an efficient release profile with a low MBC.