农药纳米载药体系对靶精准释放与剂量调控机制

The controlled and precision release of pesticide on target by nano-delivery system provides a better solution for enhancing the efficiency of pesticide utilization and reducing environmental pollution. However, the pesticide nano-delivery system still exist some problems, including single carriers structure, simple release mode and limited options for controlled release dosage. Although pesticide nano-delivery system can achieve simple, qualitative, and slow release, it is difficult to release the active ingredient consistent with the practical demand of harmful biological target, resulting in inefficient use and enormous waste of pesticide. Therefore, it has important significance to study the precision release and dosage regulation mechanism of pesticide nano-delivery system. In this project, basing on the established preparation technology of pesticide nano-delivery system using inorganic or organic material as single carrier, the pesticide nano-delivery system with novel core-shell structure will be further designed to use silica and polylactic acid as combined nano-carriers with loading typical pesticide imidacloprid. Basing on the effective dose requirement of imidacloprid for controlling aphids, the critical regulators and functional mechanism for pesticide controlled-release in nano-delivery system will be evaluated through a variety of ways, such as carrier assembly, structure design, core-shell synergistic effect and functional modification. The final intent of this research is to achieve the pesticide nano-delivery system with releasing the active ingredient maximum consistent with the practical demand. The precision release model for pesticide nano-delivery system will be established and the common scientific law will be revealed, which will provide scientific basis for the fabrication of novel pesticide formulations with sustained release function.

利用纳米载药体系实现农药对靶精准可控释放，是提高农药利用率、减少环境污染的有效途径。目前，农药纳米载药体系存在载体结构单一、释药模式简单、释放剂量调控有限等问题，虽然能够实现简单、定性的缓慢释放，却很难实现农药释放行为与最低有效防控剂量需求规律的协同，造成农药低效使用和浪费。因此，研究农药纳米载药体系对靶精准释放与剂量调控机制具有重要意义。本项目在已建立的无机及有机材料为单一载体的农药缓释体系基础上，进一步设计以多孔二氧化硅为核层、聚乳酸为壳层的有机-无机核壳复合结构载体，负载典型农药吡虫啉构建纳米载药体系；以防治甘蓝蚜虫为施药场景，利用该载药体系的多元协同调控优势，通过载体组装、结构设计、核壳协同和功能修饰，阐明控释性能的关键调控因子与作用机制，最大限度地实现药物释放特性与靶标防控剂量需求的拟合，以点带面揭示共性规律，建立精准控释农药体系的构建模式，为长效缓释农药新剂型创制提供科学依据。

控制活性成分释放速率的农药精准控释技术，可有效降低农药的挥发、分解及向非靶标环境的流失，延长农药持效期。特别是利用纳米技术将农药负载制备纳米载药体系，可以通过调节体系功能参数实现药物的控制释放。纳米农药载药体系由于其小尺寸效应和大比表面积，在改善农药叶面沉积和展布性能方面也具有一定的优势。本项目采用Stöber方法制备了孔状结构可调的核层纳米二氧化硅载体，通过吸附农药有效成分首先构建了核层纳米二氧化硅农药载药体系，在此基础上进一步采用快速膜乳化技术用聚乳酸材料进行包裹，构建了以多孔二氧化硅为核层、聚乳酸为壳层的有机-无机核壳复合结构纳米农药载药体系。通过扫描电子显微镜 (SEM)、透射电子显微镜(TEM)、红外光谱仪(FTIR)、激光粒度分布仪(LSPSDA)等对制备的纳米载药体系的粒径大小、形貌结构、表面功能基团等进行了系统地表征，优化了复合纳米载药体系的最佳功能参数和共性制备技术平台，并发展了纳米载药体系的制备新方法。通过研究载体组装、核壳协同调控、载药性能和载体降解，探索了纳米载药体系的结构优化与精准控释性能调控的途径， 通过调节纳米载药体系的孔状结构与载药特性等功能参数来改变药物的释放动力学特性，建立精准控释农药载药体系的构建模式。同时我们研究了核壳结构纳米载药体系的光解稳定性与叶面分布性，初步建立了农药纳米颗粒在活体植株上的分布性能检测方法，并进行了纳米载药体系的防控效果验证与功能优化，建立了复合载药体系的田间施药标准。本研究为创制长效缓释农药新剂型奠定了理论基础，同时促进了纳米科学与农药科学交叉研究领域的发展。