Larvicidal activity of hydrogel beads based on Pickering emulsions containing turmeric essential oil against Aedes aegypti (Diptera: Culicidae), the dengue vector.

The study aims to develop a biolarvicide alternative to synthetic insecticides for controlling Aedes aegypti (Linnaeus, 1762), a major vector for dengue, zika virus, and chikungunya viruses. Turmeric Essential oil Pickering emulsion (TEO PE) was developed to combat mosquito populations. Research offers a unique technology to encapsulate TEO PE in hydrogel beads, enhancing its larvicidal activity. The stability of TEO was enhanced using cellulose nanocrsytals (CNCs). Characteristics of CNC, PE, and hydrogel beads were evaluated using Fourier transform infrared spectroscopy (FTIR), zeta potential, Dynamic Light Scattering (DLS), SEM, and X-ray diffraction (XRD). Hydrogel beads showed effective toxicity against A. aegypti larvae in a dose-dependent method, with significant lethal concentration. FTIR analysis confirms cellulose presence in CNC, while Zeta potential and DLS show stable PE with an average particle size of 94.4 nm. Subsequently, SEM, XRD, and UV-Vis spectroscopy were performed to evaluate the crystallinity, encapsulation and release efficacy of beads, respectively. Larvicidal activity of free TEO and TEO PE-based hydrogel beads was evaluated against third instar larvae of A. aegypti. Outcome of this study demonstrated that hydrogel beads exhibit effective larvicidal activity with mortality (P < 0.001) against the larvae with significant lethal concentration (LC) values (LC50 = 227.074 mg/l ± 7.09912, LC90 = 360.257 mg/l ± 14.0808) as compared to pure TEO (LC50 = 22.8349 mg/l ± 2.28709, LC90 = 47.8297 mg/l ± 2.22492). Histo-pathological analysis revealed extensive damage to internal membranes and midgut regions of the larvae. This approach provides enhanced stability, targeted larvicidal activity, controlled release, and a sustainable alternative to synthetic insecticides.