Single cell encapsulation of Metarhizium brunneum via Pickering emulsion for biopesticide applications

A new approach for single cell microencapsulation in an oil-in-water (o/w) Pickering emulsion is presented. The water/paraffin emulsions were stabilized by amine-functionalized silica nanoparticles. The droplet size of the emulsions was highly tunable, and ranged from 1-30 µm in diameter. The controllable droplet size along with the high colloidal stability of the Pickering emulsions were harnessed to obtain single cell microencapsulation. The successful encapsulation of the conidia enthomopathogenic fungus Metarhizium brunneum by the studied Pickering emulsions was confirmed via confocal laser scanning microscopy. The resulting systems were implemented to develop a novel biopesticide formulation for arthropod pest control. The conidia incorporated in the emulsions were applied to Ricinus communis leaves by spray assay. The resulting dried paraffin/silica films formed a silica based honeycomb-like structure with an ordered hierarchical porosity that preserve individual cell encapsulation. This successful single cell encapsulation system led to a significantly high distribution of conidia cells on the leaves. The Pickering emulsion based formulation exhibited significantly higher pest control activity against Spodoptera littoralis larvae compared to the control systems, thus making it a promising cost effective, innovative approach to tackling the pest control challenge.