Complete Disruption of Bacterial DNA Integrity by Rosemary Essential Oil Nanoparticles.

Abstract The current work aimed to formulate Rosemary essential oil nanoparticles (Ros-ES-NPs) and evaluate their antimicrobial effect in comparison with free oil (Ros- ES). The obtained products (nano-formulation) are analyzed using zeta potential, electron scanning microscopy, spectrophotometric technique, and color analysis. The cytotoxic activity of Ros-ES-NPs on human lung fibroblast cell line (Wi-38) was examined in comparison with Ros- ES using MTT assay. Ros-ES exhibited dose-dependent cytotoxicity, with an IC50 of approximately 6.06 mg/ml on Wi-38. In contrast, the Ros-ES-NPs not only showed no toxicity but actually appeared to increase cell viability (up to ≈136%) possibly due to cell-stimulating effects. The antimicrobial activity of Ros-ES and Ros-ES-NPs was evaluated against three isolates of multidrug-resistant Bacteria, comprising two Gram-negative isolates (Shigella and K. pneumoniae) and one Gram-positive isolate (Streptococcus sp), alongside C. albicans as the fungal pathogen. Ros-ES-NPs showed a significant antimicrobial efficacy against all isolates under study where, at 25 mg/ml, Ros-ES inhibited K. pneumoniae and Shigella by 55.16 ± 0.09% and 76.47 ± 1.16%, respectively, whereas Ros-ES-NPs showed inhibition rates of 95.66 ± 9.74% and 87.13 ± 2.63%, respectively. For C. albicans, Ros-ES inhibited it by 68.75 ± 0.60%, while Ros-ES-NPs exhibited a higher inhibition rate of 80.73 ± 5.6%. These findings highlight the potential of Ros-ES-NPs as a safe and highly effective antimicrobial formulation, offering enhanced biocompatibility and potency compared to the free oil.