Redox/pH dual-responsive sodium alginate/cassava starch composite hydrogel beads for slow release of insecticides

Abstract

Insecticides play a crucial role in promoting crop growth and boosting crop yields. However, they also contribute to environmental pollution and pose risk to human health. To increase the utilization rate of insecticides and minimize their pollution of the soil and water environment, it is imperative to develop a green material or carrier for the controlled-release of agrochemicals including insecticides. In this study, composite hydrogel beads were successfully prepared using dialdehyde starch and sodium alginate as green-based raw materials, cystamine dihydrochloride as a cross-linking agent, and meanwhile sodium alginate was ionic cross-linked with calcium ions. As-prepared composite hydrogel beads possess pH/redox dual-responsive properties, enabling the controlled release of the insecticide dinotefuran (DIN). The properties, structure and morphology of the hydrogel beads were comprehensively characterized using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and X-ray diffraction (XRD). Additionally, the release behavior of DIN from the composite hydrogel beads under various conditions was extensively investigated. The results showed that the incorporation of dialdehyde starch significantly enhanced the encapsulation efficiency of DIN within the hydrogel bead. Moreover, the cumulative release of DIN can be precisely modulated by adjusting the release conditions or environmental stimuli; the release kinetics align with the Korsmeyer-Peppas model well. Specially, DIN release is accelerated under neutral conditions and in the presence of the reducing agent glutathione (GSH). The findings of this work are anticipated to exert a positive influence on agricultural production while also contributing to the alleviation of insecticide-related adverse environmental impacts.