Preparation and characterization of a controlled-release formulation based on carbofuran loaded in ionically cross-linked chitosan microparticles

Abstract

A controlled-release formulation (CRF) of the nematicide carbofuran (CAB) was prepared using ionically cross-linked chitosan (CHS). Four cross-linker agents were assessed, among which sulfate (SUL) obtained the highest encapsulation efficiency. Several parameters for the encapsulation of the pesticide were optimized, including pH, SUL/CHS molar ratio, stirring time, and stirring speed. The EE and the pesticide loading (PL) were 67% and 24%, respectively, in the optimized process. Scanning electron microscopy (SEM) images for empty microparticles (EMP) showed a rough and porous surface, with particle size of 1023 nm, whereas the CRF surface was found to be smoother, with a particle size of 1127 nm. The release kinetics of CAB from CRF and commercial carbofuran (CC) were evaluated in water under laboratory conditions, and the release data were fitted to the generalized Korsmeyer-Peppas model. The results indicated that the release of CAB was accomplished by a diffusion-controlled process. The CAB release from CRF was slower than that from CC, and required 6 days for 70% release, whereas CC required 5 days for 100% delivery of the pesticide. A diffusion coefficient (n) of 0.603 was determined, meaning that delivery was not governed by Fick’s laws of diffusion, but by an anomalous transport mechanism.