Preparation and application of thidiazuron nanoparticles via electrostatic self-assembly as defoliant in cotton

Nanopesticides can offer some benefits including better spreadability, leaf retention, a reduction usage of active ingredients and environmental pollution. Up to now, the green fabrication of nanopesticide is still a challenge work. In this study, the environmentally friendly thidiazuron-loaded nanoparticles (TDZ NPs) were fabricated through the electrostatic self-assembly by using two ionic polysaccharides chitosan and sulfobutylether-beta-cyclodextrin (SCD). Firstly, thidiazuron (TDZ) was encapsulated by SCD to form the anionic building block, which can form TDZ NPs with the cationic polysaccharide chitosan through the electrostatic self-assembly. The resulting TDZ NPs were in the average size of 137 +/- 28 nm, have low polydispersity index (< 0.1). Meanwhile, the TDZ NPs contain positive charge on the particle surface, which can promote the interaction with the leaf surface to improve the spreadability and retention. Moreover, the TDZ NPs can maintain stable for at least four weeks. In terms of biological testing, the defoliation rate of TDZ NPs reached 65.5 +/- 5.3%, while the defoliation rate of thidiazuron wettable powder (TDZ WP) was only 44.9 +/- 2.5%. Compared with the TDZ WP treatment, the photosynthesis of the leaf was more severely damaged and the release rate of ethylene was increased more by the TDZ NPs treatment. In addition, the expression of GhACS2, GhACO3 and GhERF113 were all up-regulated. The results indicated that TDZ NPs showed better bioactive effects than TDZ WP. And the TDZ NPs prepared by this method is of great significance in improving the quality of cotton in mechanized production, reducing environmental pollution and reducing labor input.