Optimization and Characterization of Biocompatible Oil-in-Water Nanoemulsion for Pesticide Delivery

The formation of promising oil-in-water nano emulsion suitable for pesticide delivery has been achieved by using methyl laurate as oil phase, and alkyl polyglycoside (APG) and polyoxyethylene 3-lauryl ether (C12E3) as mixed surfactant. Effects of APG and C12E3 mixing ratios, oil weight fraction, and total surfactant concentration on droplet size and distribution of the nanoemulsion were systematically investigated. Long-term stabilities of the nanoemulsions prepared with various surfactant mixing ratios were assessed by measuring droplet size at different time intervals; the results indicated that the main driving force for droplet size increase over time was Ostwald ripening. On this basis, a practical water-insoluble pesticide beta-cypermethrin (beta-CP) was incorporated into two optimized nanoemulsion systems to demonstrate potential applications. The results of dynamic light scattering (DLS) and transmission electron microscopy (TEM) measurements showed that the nanoemulsions had a nearly monodisperse droplet size distribution (PDI < 0.2) and incorporation of beta-CP had no notable effect on the size and stability of the nanoemulsions. For consideration of practical application, dilution stability and spreading properties of the pesticide-loaded nanoemulsion were studied by DLS, contact angle, and dynamic surface tension, respectively. The nanoemulsion was still homogeneous after dilution, although destabilization in droplet size was observed by DLS. The results of contact angle and dynamic surface tension demonstrated the excellent spreading performance of the optimized nanoemulsion.