Eco-friendly larvicidal agent from combined plant extracts encapsulated chitosan nanoparticles to combat dengue mosquitoes

Considering reduced environmental impact and high specificity in targeting vector organisms, the use of plant-based insecticides for dengue mosquito control is crucial in dengue disease management. We investigated the larvicidal efficacy of hot water, cold water, and water-acetone extracts of combined plant extracts of Capsicum frutescens (Naimiris) and Allium sativum (Garlic) against Aedes aegypti and Aedes albopictus larvae. The plant extract encapsulated chitosan nanoparticles were also assessed for larvicidal potential. Chitosan nanoparticles were synthesized via the ionic gelation method, employing an optimized formulation comprising 2.5% chitosan and 1.5% sodium tripolyphosphate, with stirring at 1500 rpm. The most effective plant extract was encapsulated into chitosan nanoparticles, subsequently packaged into commercially viable sachets. The water-acetone extract showed the highest larval mortality, resulting the lowest LD ₅₀ values (2051.01 and 1097.69 mg L ^-1 after 24 and 48 hours of exposure, respectively), while showing the significant synergistic activity (CI < 1). Nanoparticle characterization was conducted using Scanning Electron Microscopy and Fourier Transform Infrared Spectroscopy, revealing a nanoparticle diameter ranging from 350 to 450 nm. Approximately 96.10 ± 2.77% of combined plant mixture's water-acetone extract was successfully encapsulated within nanoparticles, with 90% of encapsulated plant extract released into the medium over a 14-day period. Semi-permeable sachet packets containing 6 g of encapsulated chitosan nanoparticles showed strong larvicidal activity for 10 days, with shelf life up to six months. These findings suggest that chitosan nanoparticles encapsulating a combination of Capsicum frutescens and Allium sativum extracts hold promise as eco-friendly larvicides against dengue vectors.