Development, Characterization and Evaluation of a Stable Eucalyptus globulus Essential Oil–Permethrin Nanoemulsion with Repellent Activity Against Aedes aegypti

Abstract

Background: Aedes aegypti is a primary vector of several clinically significant arboviruses. This study aimed to develop a nanoemulsion-based co-delivery system incorporating permethrin and Eucalyptus globulus essential oil for mosquito repellent applications.
Methods: The essential oil composition of E. globulus was determined using gas chromatography-mass spectrometry (GC-MS). Nanoemulsions were formulated using a low-energy spontaneous emulsification method and characterized for stability, droplet size distribution, and zeta potential. The optimal formulation was further examined by transmission electron microscopy (TEM) and evaluated for cytotoxicity. The repellent activity of eucalyptus essential oil, permethrin, their combinations, and the eucalyptus essential oil-permethrin nanoemulsion was assessed against female Ae. aegypti mosquitoes using the arm-in-cage assay.
Results: The nanoemulsions exhibited a mean droplet size of 93.5 nm and a zeta potential of 60–70 mV, indicating good stability. Transmission electron microscopy (TEM) confirmed the presence of spherical and uniformly dispersed droplets. The eucalyptus essential oil-permethrin nanoemulsion demonstrated strong repellency. A 3% permethrin concentration in the eucalyptus-permethrin nanoemulsion provided the maximum protection rate at 91.8%. In stability testing, the 1.5% version of the same nanoemulsion proved to be the most stable.
Conclusion: Eucalyptus globulus essential oil, especially in nanoemulsion form and combined with permethrin, shows promise as a natural repellent formulation against Ae. aegypti. However, field trials are essential to confirm these findings under natural conditions.