Fabrication of thermo-responsive multicore microcapsules using a facile extrusion process

A process employing extrusion was used to produce multicore microcapsules composed of multiple beads. The inner beads were made from κ-carrageenan (κ-c), a thermo-responsive linear sulphated polymer whose gelling temperature ranges at 40-60 °C, depending on the concentration of κ-c polymer and the amount of potassium chloride used for gelation. The resulting beads were then enveloped by chitosan through gelation with sodium triphosphate. The pesticide ammonium glufosinate was encapsulated in the κ-c/chitosan multicore microcapsules for demonstration of controlled release of the encapsulant. It was found that in response to an external stimulus, such as elevated temperature or solar simulation, the microcapsules exhibit the gradual release of encapsulated pesticide molecules from multicore microcapsules, compared with beads only. This process of making multicore microcapsules can be extended to other polymer pairs based on applications. This work is relevant to agriculture, where the controlled-release of the pesticides or fertilizers could be triggered by the sun and/or temperature changes, thus extending the residual period of the chemicals as well as decreasing the extent of pollution by leaching of abundant chemicals.