Characterization, cell toxicity, and antimicrobial activity of a carvacrol-encapsulating nanoliposomal system against Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli

Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli are the main pathogenic bacteria involved in severe, polymicrobial, and multidrug-resistant infections. For these infections to be overcome, lipid-based nanoparticles and nanoformulations such as liposomes have demonstrated marked potential in fighting bacterial infections by delivering antibacterial drugs, fusing with bacterial membranes, and promoting the direct delivery of antibacterial agents to bacteria. This study assesses the antibacterial effects of various formulations of carvacrol (CV)-encapsulating nanoliposomes on S. aureus, P. aeruginosa, and E. coli. The study further evaluates the cytotoxicity of the fabricated nanoliposomal system against human foreskin fibroblast (HFF) cells.

Various formulations of the liposomal nanosystem were first prepared through the thin film hydration method utilizing different concentrations of soy phosphatidylcholine (SPC), cholesterol (Chol), and Tween 60. The formulations were then evaluated for drug entrapment efficiency and release profiles, and the optimum formulation was determined for the experiments. The optimum formulation was then structurally analyzed, and the cytotoxicity of free CV and encapsulated CV on both bacteria and HFF cells was evaluated. 

Microbial tests revealed that CV-LPs outperform free CV regarding their antibacterial effects on the studied bacterial strains, with the maximum inhibitory effect exerted on S. aureus, followed by E. coli and P. aeruginosa. 

Furthermore, the MTT assay indicated that the cytotoxicity of CV against normal HFF cells was remarkably declined when it was encapsulated in the liposomal nanosystem.