Nanodelivery of the Gramicidin Peptide for Enhancing Antimicrobial Activity

Abstract

Gramicidin S (GraS) is an amphiphilic peptide that has emerged as an effective alternative antibiotic. However, its applicability is restricted for clinical uses due to its effect on eukaryotic cells and low aqueous solubility. In this work, a novel water‐soluble peptide formulation with bactericidal activity is developed by the incorporation of Gramicidin S in the lipid bilayer of liposomes (L‐GraS). As a result, GraS included in the lipid vesicles is stabilized in aqueous medium and showed antimicrobial activity against Staphylococcus aureus. In addition, L‐GraS reveals enhanced biocompatibility with mammalian cells in comparison with the free peptide. Molecular dynamics simulations shed light on the collective behavior between GraS peptides and liposomes from a molecular approach. The molecular dynamic simulations are in agreement with experimental results and further confirm the effective incorporation of GraS in the liposomes, letting understand the best formulation procedure of the vesicles. Therefore, the L‐GraS nanosystem presented here is an interesting alternative to conventional antibiotics, with less restrictions and promising features to improve current therapies. Practical Applications: Incorporation of GraS in liposomes is an interesting approach to increase the solubility of the peptide, thus expanding its therapeutic horizon as a promising alternative to combat bacterial colonization especially in wound infections.

Strategies for Improving Peptide Stability and Delivery

“…However, due to its hemolytic activity on the eukaryotic cells, in addition to its low water solubility, its clinical application is limited. A novel water-soluble formulation of GraS in a liposome bilayer enhanced its bioavailability as well as the affinity of peptides towards the cell membranes, providing an effective mechanism to kill bacteria [ 68 ]. To circumvent the solubility obstacle of GraS, Desimone and coworkers developed the formulations that can hold the GraS in dipalmitoylphosphatidylcholine (DPPC) and dimyristoylphosphocholine (DMPC) liposomes (L-GraS).…”

“…To circumvent the solubility obstacle of GraS, Desimone and coworkers developed the formulations that can hold the GraS in dipalmitoylphosphatidylcholine (DPPC) and dimyristoylphosphocholine (DMPC) liposomes (L-GraS). Molecular dynamics simulations were also performed to analyze the encapsulation mechanism [ 68 ]. These liposome formulations must be designed carefully, such that the liposomal membrane must adapt the conditions of the therapeutic target.…”

“…These liposome formulations must be designed carefully, such that the liposomal membrane must adapt the conditions of the therapeutic target. For example, it is known that wound-infected areas have a 2 °C higher temperature; thus, modifying the liposomal composition is important to control the permeability and the release patterns [ 68 ]. DPPC and DMPC were mixed with various ratios of cholesterol, hydrated, and then extruded.…”

“…The liposomes vesicles were obtained used a formulation of DPPC:DMPC:Cholesterol (7:2:1). After obtaining the lipid–GraS film, it was extruded several times at a temperature higher than the melting point to achieve the unilamellar and monodisperse vesicles [ 68 ].…”

“…Interestingly, the GraS maintained its antimicrobial activity with the minimum inhibitory concentration of 0.1 mg/mL versus 0.025 mg/mL for the free GraS. According to the cytotoxic behavior of the liposomal peptide, the best relationship between the antibacterial activity and biocompatibility is to have 0.3 mg/mL of the peptide in the formulation [ 68 ].…”