Preparo e caracterização de micropartículas poliméricas para a liberação controlada do herbicida Imazetapir

Abstract

The development of novel devices able to tailor the physiological, physicochemical and, also, control the release of herbicides is one of the most promising strategies to reduce their use and harmful effects. In this sense, this Dissertation describes the preparation of alginate (Alg) and alginate/cellulose (Alg/CL) microparticles and investigates their use as vehicles for controlled release of imazethapyr (IMZ). The chemical nature, structure, and morphology of the prepared microparticles was characterized by different techniques (SEM, FTIR, XRD, TG/DTG) in detail. With the analytical data, it was confirmed the incorporation of CL into the Alg matrix and also the efficient encapsulation of IMZ into the Alg and Alg/CL microparticles. It was observed that the IMZ molecules undergo a phase transition from crystalline to the amorphous state after the encapsulation process suggesting that the herbicide and the polymeric microparticles may interact. As noticed from in vitro release assays, the IMZ is released slowly from the microparticles, which did not occur with pure IMZ (not encapsulated). Also, the presence of CL into the microparticles slow down the IMZ release rate as comprared to the pristine microparticle. The experimental data were fitted by mathematical models, which revealed that the herbicide release from the microparticles is governed by a Fickian diffusion mechanism, described by the Korsmeyer-Peppas kinetic model. In conclusion, the results presented in this Dissertation allow inferring that these microparticles (Alg and Alg/CL) can be ranked as promising devices to act as vehicles for controlled release of IMZ in practical applications. As assessed, such microparticles can sustain the herbicide level in the crop field for at least 30 days, which is attractive from the practical viewpoint.