ATRP改性壳聚糖农药载体的设计及控制释放性能研究

The technology of controlled release of pesticide provides a better solution for enhancing the efficiency of pesticide utilization and reducing the pesticide residue and environmental pollution. The performance of the carriers for controlled release pesticide formulation is crucial. Cheap and environmental friendly chitosan has great potential for development and application prospect in controlled release pesticide formulation research. However, when hydrophobic pesticides were loaded with chitosan and its derivatives as carriers, the loading content and release characteristics were not satisfactory. To the best of our knowledgement, chitosan derivatives chemically modified by controlled/living atom-transfer radical polymerization (ATRP) reaction as carriers for controlled release pesticide formulation has not been reported. In this project the novel amphiphilic chitosan copolymer was prepared by ATRP reactions and used as carriers for establishment of the pesticide-loaded microspheres with pyraclostrobin as model pesticide. Then the loading content and in vitro release kinetics of pyraclostrobin were studied and the inherent relationship between the microscopic chemical structure and macroscopic loading content and release profile was evaluated, which provide theoretical guidance for the optimization of formulation design. The pesticide loading content and release characteristics can be controlled by controllable ATRP reactions through the non-covalent bond interaction between the hydrophobic segment of chitosan copolymer and hydrophobic pesticide. The implement of this project will provide new idea to improve the loading content and fabricate novel pesticide formulations which release the active ingredient consistent with the practical demand.

控制释放技术是目前提高农药有效利用率、减少农药残留与环境污染问题的有效途径，其中载体材料的性能是关键。具有价廉、环境相容性好等众多优点的壳聚糖在农药控制释放研究中已表现出广阔的应用前景，但存在对脂溶性农药载药量低、释放可控性不强等局限性。本项目选用含典型官能团的烯烃单体，采用集自由基聚合与活性/可控聚合优点于一体的原子转移自由基聚合（ATRP）反应修饰改性壳聚糖，制备系列新型两亲性壳聚糖接枝共聚物。以吡唑醚菌酯为模式药物构建载药体系，进行载药量和释放动力学等研究，以期明确ATRP修饰改性壳聚糖微观化学结构与宏观载药量和可控释放性能之间的内在规律，为优化农药载体设计提供理论指导。本研究在国内外首次通过可控ATRP反应接枝不同疏水片段化学改性壳聚糖，改善其与脂溶性农药分子之间的相互作用，为提高农药载药量和构建释放时间与剂量符合实际防控需求的农药新剂型提供新的思路。

控制释放技术是目前提高农药有效利用率、减少农药残留与环境污染问题的有效途径，其中载体材料的性能是关键。本项目围绕壳聚糖进行化学改性，探讨农药载药量和释放性能与载体化学结构的内在关系。（1）利用壳聚糖和甲基丙烯酸甲酯为壁材，采用自由基聚合法制备了氟乐灵微囊，并测定其形态、粒径及其分布、包封率和载药量，同时研究其释放性能及其在土壤和水中的光稳定性。结果表明：所制备的氟乐灵微囊呈规则球形；粒径在 3～10 μm之间；包封率和载药量分别为79%和 45%；释放以Fick 扩散为主；与氟乐灵乳油相比，氟乐灵微囊的光稳定性显著增强，在试验条件下，其在土壤表面和水中的光解半衰期分别为22 d和173 min。（2）以生物可降解的壳聚糖和D, L-丙交酯为原料，利用开环聚合法合成壳聚糖-聚乳酸接枝共聚物，并以其为壁材，以嘧菌酯为芯材，以聚乙烯醇（PVA）为连续相稳定剂，采用乳化溶剂挥发法制备了不同粒径的嘧菌酯微囊，研究了芯壁材质量比、PVA质量分数、油水相比例、剪切速率及时间对微囊形态、粒径及分布、包封率和载药量的影响，探讨了微囊制备工艺条件及粒径调控方法。结果表明：在PVA质量分数为 1%，油水相比为1:10，剪切乳化时间为5 min，在3000～18000 r/min之间通过调节剪切速率，可制备出形状规则、粒径在280 nm～4.5μm之间并具有良好缓释性能的嘧菌酯微囊，其中剪切速率是影响微囊粒径的主要因素。（3）通过介孔二氧化硅和壳聚糖季铵盐的静电吸附作用，提高吡唑醚菌酯的载药量，并调控其释放性能和生物活性。（4）在利用壳聚糖作为材料进行农药控制释放制剂研究过程中，发展了壳聚糖降解产物氨基寡糖素的高效阴离子交换色谱-脉冲安培检测分析方法以及氨基寡糖素中无机阴阳离子测定的离子色谱分析方法。