Stearic acid-based nanoparticles loaded with antibacterial peptides – Bacitracin and LL-37: Selection of manufacturing parameters, cytocompatibility, and antibacterial efficacy

Solid lipid nanoparticles are currently one of the most widely investigated types of drug delivery carriers. Considering the fact that their clinical translation boosted after the approval of two COVID-19 mRNA vaccines, it is crucial to fully explain how the processing parameters affect the properties of the obtained nanoparticles and the drug loading efficiency. This study aimed to evaluate the influence of different manufacturing parameters on the properties of stearic acid-based nanoparticles fabricated using the emulsification/solvent diffusion method. It was found that the type of organic solvent used has a major effect on the morphology of the nanoparticles, with chloroform being suitable for the production of spherical nanoparticles. The size and polydispersity of the nanoparticles were affected by the concentration of surfactant in the external aqueous phase, the concentration of stearic acid in the organic phase, and the homogenization amplitude. The optimized nanoparticles were successfully loaded with an antibacterial peptide – LL-37. The presence of LL-37 did not significantly influence nanoparticle morphology or cytocompatibility. The obtained nanoparticles showed antibacterial activity against the reference strain of Streptococcus pyogenes (ATCC 12384). The developed solid lipid nanoparticles are promising drug carries that can be further optimized for the treatment of infected wounds or bacterial infections in the respiratory system.