Double-Shell Lignin Nanocapsules Are a Stable Vehicle for Fungicide Encapsulation and Release
Raisa Carmen Andeme Ela, Momoko Tajiri, Nick K. Newberry, Patricia A. Heiden, Rebecca G. Ong
Abstract
Industry is increasingly turning to biobased and environmentally benign materials for use in high-value applications. Kraft lignin’s low cost and inherent properties, such as its easily tunable amphiphilic nature, adsorption capacity, and natural cross-linking tendency, make it suitable for use as a raw material for high-value nanomaterials. To support that need, this paper describes the synthesis of innovative, double-shelled lignin nanocapsules from hardwood kraft lignin, their performance towards encapsulating a fungicide, and effectiveness at controlling its release. The recovered lignin was dissolved without further modification in tetrahydrofuran and inserted dropwise into a water/ethanol solution containing sacrificial surfactant templates. Monodispersed, hollow, double-shell nanocapsules were produced via a two-step self-assembly. The water/ethanol solution acted as a nonsolvent while simultaneously providing strategic sites for controlled-size production. The shells of the nanocapsules were cross-linked with biodegradable maleic anhydride to bolster the structural stability. The average hydrodynamic diameter of the particles was 241.8 ± 33.3 nm, and these structures were stable in water for a period of eight months. The specific surface area of kraft lignin increased by 4-fold in the double-shell nanocapsule form. The nanocapsules were loaded with propiconazole at an entrapment efficiency of 56.1%. This system could represent an effective method to enable biologically activated, controlled release of fungicides.