Synthesis And Properties Of Amphiphilic Grafted Copolymer Chitosan-Poly(Iactide) As Fungicide Carrier

Amphiphilic copolymer consists of hydrophilic part and hydrophobic part in the structure. Thecopolymer can form a core-shell structure of polymer micelles with hydrophobic inner core andhydrophilic outer shell in aqueous media， owing to its unique chemical structure. As novel drugdelivery systems， copolymer micelles have unique advantages in poorly water-soluble drugs， andhave received special attention in pharmaceutical field. Due to the similarities between pharmaceuticalformulations and pesticide formulations， the problems of pesticide formulations could be solved on thebasis of medical applications. In this paper， amphiphilic grafted copolymer chitosan-poly(lactide) wassynthesized. The chemical structure and physical properties of the copolymer were characterized. Theperformance of the amphiphilic copolymer micelles as an agricultural fungicide carrier were explored.Chitosan-poly(lactide) grafting copolymer (CS-co-PLA) with hydrophobic poly(lactide)(PLA)moiety and a hydrophilic chitosan segment, was synthesized by Ring-Opening method. The copolymerwas characterized by FT-IR，1H NMR，GPC and thermogravimetric analysis (TGA). The fluorescenceexperiments showed that the copolymer had a very low critical micelle concentrations (CMC). Thedynamic light scattering (DLS) and scanning electron microscope (SEM) indicated that thenanoparticles dispersed as individual particles with a well-defined spherical shape and homogeneousdistribution.The flusilazole-loaded and difenoconazole-loaded CS-co-PLA copolymer nanoparticles wereprepared by nanoprecipitaion and emulsion/solvent evaporation methods. Different factors whichinfluence on particle size， size distribution， encapsulation dfficiency (EE)， drug-loaded content(LC)and fungicide release behavior were investigated by dynamic light scattering (DLS) and highperformance liquid chromatography (HPLC). Results showed that the fabrication method offungicide-loaded nanoparticles， mass ratio of fungicide to copolymer made a great influence on theparticle size， size distribution， EE， LC， and fungicide release behavior. As the mass ratio offlusilazole/difenoconazole to copolymer increased， the nanoparticle particles size， EE and LCincreased. The nanoparticles provided a controlled release of flusilazole and difenoconazole.Biological studies have been performed on grape leaves to estimate the penetration level offungicide-loaded nanoparticles through the epicuticular wax， compared to classical40%flusilazoleemulsifiable concentrate (EC) and20%difenoconazole water dispersible granules (WDG). It wasconcluded that compared to the classical EC and WDG, the penetration rate of flusilazole-loaded anddifenoconazole-loaded nanoparticles were increased by13.6%and17.1%respectively.