Polymeric encapsulation of anti-larval essential oil nanoemulsion for controlled release of bioactive compounds

Abstract

In the present study, polymeric encapsulation of lemongrass oil nanoemulsion was done for the controlled release of bioactive compounds. O/W nanoemulsion was prepared from lemongrass essential oil, non-ionic surfactant polysorbate80 and water by spontaneous emulsification method. Geranial and neral were found to be the major bioactive compounds, constituting 45.1 % and 31.1 % of total lemongrass essential oil. The optimized lemongrass oil nanoemulsion was formulated with the droplet diameter of 14.4 nm and polydispersity index of 0.111. Transmission electron micrographs revealed that the nanoemulsion droplets were spherical in morphology and were in the size range of 10–100 nm. The optimized nanoemulsion was encapsulated with chitosan polymer by using glutaraldehyde as a cross-linking agent. Encapsulation of essential oil nanoemulsion was optimized for the process parameters such as chitosan concentration and nanoemulsion concentration in order to obtain applicable encapsulation with enhanced release of lemongrass oil. The essential oil-loaded microcapsules were spherical and smooth in shape as revealed by phase contrast microscopy and scanning electron microscopy (SEM) with the diameter of 0.53 ± 0.02 mm. Mosquito larvicidal activity of encapsulated essential oil nanoemulsion was better against malaria vectors Anopheles stephensi and Anopheles culicifacies when compared to non-encapsulated nanoemulsion, due to the controlled release of the bioactive components. The results of this study will be helpful for future vector control strategies as we provided a practical combined technique of nanoemulsion formulation and polymeric encapsulation as potential delivery system of hydrophobic bioactive compounds against mosquito vector.