Double-Shell Lignin Nanocapsules Are a Stable Vehicle for Fungicide Encapsulation and Release

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.

Recent Advances on Lignocellulosic-Based Nanopesticides for Agricultural Applications

“…Kraft lignin (KL) has a tunable amphiphilic nature due to the abundant phenolic hydroxyl groups capable of forming a stable double-layered nanomaterial with ionic surfactants (Ela et al, 2020), nanocapsules with olive oil (Falsini et al, 2020), and is also able to chelate cationic metals (Sipponen et al, 2017). Other nanopesticides have also been synthesized with alkali lignin (AL) (Yin et al, 2020), organosolv lignin (Zhang et al, 2020a), and methacrylate lignin (Yiamsawas et al, 2021).…”

Lignin–Propiconazole Nanocapsules are an Effective Bio-Based Wood Preservative

“…In this work, double-shelled nanocapsules were produced from kraft lignin to overcome the hydrophobicity of the raw material and to serve as a carrier for the organic antifungal, propiconazole. The lignin nanocapsules were highly dispersible and stable in water, and by containing and controlling the release of propiconazole, they could increase the amount of fungicide that penetrates the wood. Southern yellow pine was pressure and dip treated using empty and propiconazole-loaded lignin nanocapsules; the loading efficiencies, and the extent of penetration of the loaded nanocapsules into the wood were evaluated.…”

Innovative Sustainable Wood Preservatives From Pulp and Paper Industry Byproduct

“…Lignin-propiconazole nanocapsule synthesis. The method for preparing loaded nanocapsules is as reported in our previous work [237]. Briefly, 1 g of kraft lignin was dissolved in 35 mL of tetrahydrofuran.…”

“…A solution of the free-radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) in methanol (40 µg/ml) was prepared, and the absorbance maxima measured using a UV-Vis-NIR spectrophotometer (Shimadzu UV-3600 Plus) at 517 nm against methanol. The anti-fungal nanocapsule systems are comprised of particles that are well-dispersed and stable in water (DS+PCZ, 424.6 ± 17.1 nm, -27.1 ± 1.5 mV) [237]. These properties are important to ensure the nanocapsules do not settle and impede treatment.…”

“…In this work, double-shelled nanocapsules were produced from kraft lignin to overcome the hydrophobicity of the raw material and to serve as a carrier for the organic antifungal, propiconazole. The lignin nanocapsules were highly dispersible and stable in water [237], and by containing and controlling the release of propiconazole, could increase the amount of fungicide that penetrates the wood. Southern yellow pine was pressure and dip treated using empty and propiconazole-loaded lignin nanocapsules and the loading and penetration of the nanocapsules into the wood were evaluated.…”