Increasing the stability and antimicrobial activity of antimicrobial peptides after association to Lipid nanocapsules

Introduction: Resistant infections are estimated to be responsible of 700.000 deaths worldwide. These figures, often underestimated highlight the importance of the antimicrobial resistance (AMR). Education toward the misuse of... [ view full abstract ]

Introduction:
Resistant infections are estimated to be responsible of 700.000 deaths worldwide. These figures, often underestimated highlight the importance of the antimicrobial resistance (AMR). Education toward the misuse of antibiotics is no more sufficient. Finding new therapies to overcome resistance becomes imperative. Antimicrobial peptides are under the spotlight. Their ability to act rapidly, at low concentrations and in a not specific way makes them interesting antibiotic molecules with less potential to induce resistance. Nevertheless, their development is hampered by physico-chemical and biological instabilities.
The aim of this work is to explore the potential of lipid nanocapsules (LNCs) to deliver AA230, DPK060 and LL37, three cationic, hydrophilic and biosourced antimicrobial peptides.
Methods:
Peptide adsorption on the surface of the LNCs (LNC-AMP) and/or encapsulation within their lipidic core (LNC-RM-AMP) was performed. The in vitro antimicrobial activity of the AMPs and nanoformulated AMPs was assessed by the determination of the minimal inhibitory concentrations against different Gram (-) and Gram (+) bacteria and The kinectics of the inhibitory effect was conducted for each formulation against the sensitive strains. Proteolysis assays was performed to invetigate peptides stability after association.
Results:
The results showed a good association efficiency after adsorption to the surface of LNCs. The encapsulation in the core succeeded except for the peptide AA230. The antimicrobial activity was preserved in all cases. Moreover, a potentiation of the in vitro anti-bacterial activity, reflected by a lower minimal inhibitory concentrations (MICs) was observed for the adsorbed peptides. The time kill-kinetics studies confirm the bactericidal killing of the nanoformulated peptides at concentrations up to 8 times lower than the MIC of the peptide alone. Moreover, proteolysis assays performed with trypsin as model enzyme, demonstrated a partial protection of adsorbed LL37 against proteolytic degradation compared to the plain peptide over 4hours.
Discussion:
Overall, these data indicated that LNCs are promising nanocarriers for the delivery of AMPs. The two strategies studied are to be investigated. The better knowledge of the peptide properties and the exploration of the mechanism of action responsible of the synergistic effect will definitely contribute to consolidate the potential of such nanoformulated peptides as next-generation antibiotics.