Instantaneous and Continuous Preparation of Avermectin Nanoparticles with High Gravity Anti-Solvent Precipitation Technology

The inherent insolubility of avermectin (Av) in water and its easy degradation property prompt the abuse of organic solvents, leading to a decreased rate of pesticide utilization and natural damage. Herein, we propose an effective approach to continuously synthesize avermectin nanoparticles (nano Av) with relatively small size and enhanced performance by high gravity anti-solvent precipitation in a rotating packed bed (RPB). Compared with the conventional stirred tank reactor (STR) method, the average particle size of as-prepared products can be decreased from 166 to 66 nm. Importantly, the preparation time can be greatly reduced from 60 min to 1 s. The addition of polyvinylpyrrolidone (PVP) effectively avoids the agglomeration of nanoparticles by electrostatic and steric stabilization, thereby obtaining the spherical and well-dispersed nano Av. Remarkably, nano Av prepared in RPB exhibits higher drug loading capacity and better anti-UV performance and wettability than the STR products. Compared to technical avermectin, the as-prepared Av using RPB shows prolonged efficacy and displays a better killing effect for Plutella xylostella. The biosafety evaluations on nontarget organisms indicate that PVP is safe for Escherichia coli, seeds, and plants. This novel method could provide a platform for the development of nanopesticides with potential applications.