Optimization and in vitroCharacterization of Piperine-lemongrassLoaded Nanoemulsions GreenLarvicide for Aedes aegypti

Abstract

Aim: Aedes aegypti is a major vector for dengue and Zika. Rising resistance to synthetic pesticides has shifted focus
toward botanical larvicides like piperine and lemongrass oil. However, these actives suffer from high hydrophobicity
and environmental instability. This study aimed to develop stable, green nanoemulsions to enhance their delivery and
larvicidal efficacy. Material and Methods: Active ingredients included piperine and lemongrass oil . The oil phase
utilized olive oil, while Tween 80 and propylene glycol served as surfactant and co-surfactant. Distilled water formed
the aqueous phase, with ethanol and methanol (S.D. Fine chemicals) used as analytical reagents. Triethanolamine and
citric acid were employed for pH adjustment. Nine formulations (F1–F9) were designed using a 32 factorial model and
prepared via low-energy emulsification followed by ultrasonication (650W, 20 kHz). Characterization was performed
using Dynamic Light Scattering (DLS), Transmission Electron Microscopy (TEM), and UV-Vis spectrophotometry
.Results and Discussion: Formulation F9 was identified as the lead system, containing 3.0% piperine and 3.0%
lemongrass oil. It exhibited an optimal droplet size of 28.1±1.1 nm, a PDI of 0.165, and a zeta potential of −34.8±5.0
mV, indicating high colloidal stability. F9 demonstrated superior larvicidal potency with an LC50 of 28.5 μg/mL
and 89% mortality after 48 hours. The nano-sized droplets improved penetration and contact with the larval cuticle,
leading to physiological disruption and gut paralysis. Conclusion: The study successfully optimized a dual-active
nanoemulsion that provides a 2- to 4-fold increase in efficacy over free botanical extracts. These green nanoemulsions
represent a sustainable, biodegradable, and highly effective alternative for integrated mosquito management.