Multifunctional Arginine-Modified Chitosan/Chitooligosaccharide Microcapsules for pH-Responsive Pesticide Delivery

The development of novel pesticide formulations with the minimization of the adverse impact and simultaneous maximization of utilization efficiency is highly urgent. A new window for pesticide delivery has been created for green and sustainable agriculture using chitosan (CS) and chitooligosaccharide (COS) as carrier materials because of their economic, biocompatibility, and versatile functional properties. However, the difference of properties between CS and COS is not well clarified in pesticide delivery. In this study, pyraclostrobin (PYR)-loaded microcapsules based on arginine-modified CS (PYR@CS-Arg) or COS (PYR@COS-Arg) were successfully prepared through an electrostatic self-assembly strategy. Notably, in addition to possessing pH-responsive release characteristics, PYR@CS-Arg exhibited faster release kinetics in alkaline environments compared to PYR@COS-Arg, attributed to the formation of a larger space following CS-Arg dissociation from microcapsules. Comparative analysis with other formulations revealed that both PYR@CS-Arg and PYR@COS-Arg demonstrated superior performance in terms of target deposition, bioactivity, UV stability, biosafety, and nutritional function. These characteristics significantly enhance the pesticide utilization rate while reducing environmental risks, aligning with the principles of sustainable agricultural development. Owing to the multifunctional properties of COS, PYR@COS-Arg showed enhanced performance in maximum retention, fungicidal activity, UV protection, and plant growth promotion compared to PYR@CS-Arg. Conversely, PYR@CS-Arg exhibited lower nontarget organism acute toxicity, owing to its larger particle size facilitating gravitational sedimentation in aqueous environments. These findings provide valuable insights into carrier material selection based on application scenarios and target control requirements, offering a promising and practical strategy in sustainable agricultural practices.