Structural and bactericidal properties of imidazolium ionic liquid-based micelles of thyme essential oil

Abstract

We report the structural and bactericidal properties of the imidazolium ionic liquid (IL)-based micelles of Thymus capitatus (thyme) essential oil (EO). The formation of micelles was investigated by contact angle measurements, which revealed a critical micelle concentration (CMC) of 2.5–3 µM for the IL mixed with thyme at 0.2 µL mL⁻¹. The size, stability and self-assembly of EO-IL micelles in water were evaluated by the dynamic light scattering technique. It was determined that the self-dispersed micelles with a ∼400 nm diameter remained stable in a water environment for at least 6 months from their formation. The bactericidal properties of micelles investigated against S. aureus and E. coli under liquid-to-liquid conditions revealed a 6-log reduction in the bacterial concentration from 10⁸ CFU mL⁻¹ following 1 min exposure. Minimal bactericidal growth of both bacteria was observed under the CMC conditions. These results demonstrate the potential of EO-IL micelles as natural agents that self-disperse in water and kill bacteria at rapid rates.