Alginate-cellulose biopolymeric beads as efficient vehicles for encapsulation and slow-release of herbicide

Abstract

Alginate (ALG) and alginate/cellulose (ALG/CEL) beads were prepared and tested as potential vehicles for encapsulation and controlled release of imazethapyr (IMZ), a broad spectrum herbicide. The incorporation of a small amount of CEL (5 w/w-%) into the ALG network allowed to increase the encapsulation efficiency of IMZ (>85%). CEL also contributed to control of some important features such as the effect of pH on the liquid uptaking and stability in water. Release profile of IMZ from the prepared beads (ALG@IMZ and ALG/CEL@IMZ) was assessed in water, and it revealed that these carrier devices behaved as slow release formulations as compared to pure IMZ. Moreover, CEL-containing beads reduced the release of IMZ more efficiently than the pristine ALG beads. The release profiles of both carrier systems were well fitted by the Korsmeyer-Peppas model, which indicated that in both cases the IMZ release is driven by Fickian diffusion mechanism. The time taken for 50% of IMZ to be release was 11.30 days for ALG beads, while for the ALG/CEL beads this time was increased to 43.73 days. The experimental performance presented by ALG and ALG/CEL beads demonstrated that both systems could control and prolong the release of IMZ, which is paramount for their practical application as slow-release systems.