Individual Coating of Entomopathogenic Nematodes with Titania (TiO2) Nanoparticles Based on Oil-in-Water Pickering Emulsion: A New Formulation for Biopesticides

This study presents a new eco-friendly formulation of entomopathogenic nematodes (EPNs) based on individual coating of EPNs with titanium dioxide (TiO2) nanoparticles (NPs) and mineral oil via oil-in-water Pickering emulsions. Mineral oil-in-water emulsions stabilized by amine-functionalized titanium dioxide (TiO2-NH2) particles were prepared. 40:60 and 50:50 oil-water volume ratios using 2 wt % TiO2-NH2 particles were found to be the most stable emulsions with a droplet size suitable for the formulation and were further studied for their toxicity against the incorporated EPNs. Carboxyfluorescein was covalently bonded to TiO2-NH2 NPs, and the resulting composite was observed via fluorescence confocal microscopy. The dry coating was evaluated using SEM and confocal microscopy, which showed significant nematode coverage by the particles and oil. The final formulation was biocompatible with the studied EPNs, where the viability of the EPNs in the formulation was equivalent to control aqueous suspension after 120 days. Finally, yields of nematodes from infected Galleria mellonella cadavers collected for 150 days showed no significant differences (P > 0.05) using the tested emulsions compared to the control containing nematodes in water.