Eggshell-derived Hydroxyapatite Nanocarriers for Neem Oil based Nanoemulsion: Toward Sustainable Pest Control

The impact of pests on crop productivity requires an effective and sustainable alternatives to synthetic pesticides, as it pose risks to human health and the environment. The green formulation of a nanoemulsion pesticide by encapsulating into Hydroxyapatite Nanoparticles (HANPs) synthesized from waste eggshells is the main aim of this research. The nanoemulsion formulation, containing neem oil (1.75%), lemon peel oil (0.25%), soapnut extract (4%), and water (94%), was prepared using ultrasonication. Dynamic Light Scattering (DLS) confirmed the high stability of the resulting ~200 nm droplets.  X-ray Diffraction (XRD) verified the crystalline nature of HANPs, while Fourier Transform Infrared (FTIR) Spectral Analysis confirmed successful neem oil presence. In vitro release studies demonstrated an initial burst release (~15% within 5 days), followed by sustained release (~100% by day 70) consistent with Higuchi kinetics (R² = 0.9892). Aphid mortality increased with both time and concentration, reaching complete mortality at 1.75% (v/v) after 12 hours. The LC₅₀ values declined from 1.375% (v/v) at 2 hours to 0.893% (v/v) at 12 hours, indicating enhanced toxicity with prolonged exposure. ANOVA, based on a Box-Behnken design, indicated that neem and lemon peel oil concentrations significantly affected efficacy (p < 0.001). Field trials showed complete Aphid elimination on Solanum lycopersicum, Solanum melongena, and Allium cepa, with no signs of phytotoxicity or harm to non-target organisms.The present study formulates an effective pest control through prolonged delivery of active compounds, offering a cost-effective and environmentally responsible solution for modern agricultural practices.