Eco-safe citral nanoemulsion for Aedes albopictus control: Mechanistic multi-target toxicological evaluation...

The widespread transmission of mosquito-borne diseases such as dengue, chikungunya, Zika, and yellow fever by Aedes albopictus necessitates environmentally sustainable vector control solutions. This study developed and characterized a citral-based nanoemulsion using Tween 80 via low-energy emulsification, aiming to enhance larvicidal efficacy and environmental safety. Larvicidal bioassays against third instar A. albopictus revealed significantly higher potency for citral nanoemulsion (LC₅₀: 18.886 mg/L; LC₉₀: 78.209 mg/L) compared to unformulated citral (LC₅₀: 25.777 mg/L; LC₉₀: 99.481 mg/L). Morphological study and SEM analysis demonstrated severe structural damage in nanoemulsion-treated larvae, including cuticle collapse, spiracle deformation, and anal gill disfigurement. Biochemical assays indicated elevated catalase (CAT), superoxide dismutase (SOD) and malondialdehyde (MDA) levels, suggesting oxidative stress induction. Molecular docking revealed moderate to high binding affinities of citral to CAT (-6.3 kcal/mol), SOD (-4.5 kcal/mol), acetylcholine receptor (AChR; -6.0 kcal/mol), and juvenile hormone-binding protein (JHBP; -7.0 kcal/mol), involving hydrogen bonding and hydrophobic interactions. These interactions imply multi-target disruption of antioxidant defence, neural signalling, and endocrine regulation, contributing to larval mortality. Environmental safety evaluation using Chironomus larvae showed low acute toxicity (<10% immobilization at 52.136 mg/L), indicating selective action toward target species. Collectively, the findings highlight citral nanoemulsion as a potent, biodegradable and target-specific larvicide with minimal non-target effects, aligning with sustainable mosquito control strategies. Future work should focus on field validation, adult mosquito susceptibility, and chronic ecological safety to facilitate large-scale application.