Essential Oils Nanoemulsions: ‎Preparation, Characterization and Study of ‎Antibacterial Activity against Escherichia ‎Coli

   This research studies the application of essential oil nanoemulsion as herbal medicine instead of using antibiotics and chemicals. Thyme, shirazi thyme and rosemary essential oils were selected as herbal drugs. Essential oil nanoemulsions with Tween 80 and/or Sodium dodecyl sulfate (SDS) surfactants were prepared and investigated. Physicochemical characterizations such as hydrodynamic diameter, pH, conductivity, optical clarity and antibacterial activity against gram negative bacteria, E.coli, have been studied. Morphology of the nanoemulsions was evaluated by transmission electron microscope (TEM). Nanoemulsions prepared with the mixture of SDS−Tween 80 had particle diameters significantly smaller than those prepared with Tween 80 (2-11.7 nm in comparison with 189-200 nm). Formulated nanoemulsions had long-term stability at ambient temperature; as there were little changes in droplet diameter after storage for 2 months. MTT assay showed non-toxicity of prepared nanoemulsions. Antibacterial activity against E.coli was also studied by counting the number of survival bacteria in a broth medium. The in vitro test indicated efficacy of all prepared emulsions on E.coli, especially those containing thyme essential oil. The results suggested that the formulated nanoemulsions might be used as potential carrier in food, pharmaceutical and drug delivery systems.