叶面亲和型阿维菌素微胶囊的制备及pH响应性释放性能

Preparation and pH responsive release properties of foliar affinity avermectin microcapsules

为减少农药流失,设计了一种叶面亲和型缓释微胶囊。以甲基丙烯酸甲酯(MMA)接枝改性羧甲基纤维素(CMC)得到羧甲基纤维素-聚甲基丙烯酸甲酯(CMC-g-PMMA),然后利用自组装负载阿维菌素(AVM)形成载药微胶囊(CMC-g-PMMA@AVM),通过多巴胺(DA)包覆提高CMC-g-PMMA@AVM的叶面亲和性。采用扫描电镜、红外光谱、热重分析等对其结构和形貌进行表征,研究了微胶囊的载药性能、叶面亲和性及响应释放性能。结果显示,DA/CMC-g-PMMA@AVM为平均粒径126nm的球形粒子,多巴胺的包覆可有效提高微胶囊的载药性能,包封率可达88.56%;增强AVM的叶面亲和性,使其叶面滞留量相对于阿维菌素水乳液提升30.56%;赋予AVM优异的抗紫外光分解性能,强紫外光照射60min后,由AVM水乳液中AVM的残留率14.03%提高到DA/CMC-g-PMMA@AVM中的59.55%。载药微胶囊中药物释放具有p H响应,在pH=5条件下出现爆释,药物释放过程符合Weibull模型,受Fick扩散控制。

In order to reduce the loss of pesticides, a foliar affinity sustained-release microcapsules was designed. Polymethyl methacrylate(PMMA) was used to modify carboxymethyl cellulose(CMC), and then avermectin(AVM) was coated by self-assembly to form drug-loaded microcapsules(CMC-gPMMA@AVM). The dopamine coating was then used to form affinity microcapsules(DA/CMC-gPMMA@AVM). The structure and morphology were characterized by scanning electron microscopy,infrared spectroscopy and thermogravimetric analysis. The drug loading, leaf surface wetting and pHresponsive drug release properties were studied. The results showed that DA/CMC-g-PMMA@AVM was a spherical particle with an average particle size of 126 nm. The coating of dopamine can effectively improve the drug loading performance of the microsphere and increase the encapsulation efficiency to 88.56%. The leaf affinity of AVM was enhanced and the leaf retention was increased by 30.56% relative to the emulsion of avermectin. The residual rate of AVM in AVM emulsion was only 14.03% after strong ultraviolet irradiation for 60 min, while up to 59.55% in DA/CMC-g-PMMA@AVM. The drug release in the microcapsules had a pH response, and a burst release phenomenon occurred at pH=5. The release process conformd to the Weibull model and was controlled by Fick diffusion.