Green liquid marble-based hydrogels as pesticidal pyrethrin slow-release carriers†

Abstract

Pyrethrins are effective agents against mosquito larvae, but their rapid degradation rate in water reduces their deinsectization efficiency and increases the cost of deinsectization. Based on liquid marbles, a biodegradable slow-release hydrogel carrier is prepared using green and low-cost materials for the slow release of natural pyrethrin on water surfaces to kill mosquito larvae. Green carriers with high stability and loading of high concentrations of pyrethrin are synthesized by cross-linking Ca²⁺ in 5% CaCl₂ solution with sodium alginate. The superior stability of liquid marbles at the water surface and the electrostatic interaction between alginate and gelatin can effectively reduce the degradation rate of pyrethrin in water. Furthermore, the carrier system displayed a long sustained-release time (>144 h) and maintained larvicidal performance after 168 h. Good floating stability is demonstrated for the liquid marble hydrogels. The larvicidal activity of the obtained drug carrier reached 100% with different water volumes but the same dosage. This work provides a strategy to exterminate mosquito larvae with high efficiency by preparing a green hydrogel drug slow-release carrier, thus providing a new approach to expanding the application of liquid marbles in green chemistry.