Pesticide-Loaded Nanocarriers from Lignin Sulfonates—A Promising Tool for Sustainable Plant Protection

Abstract

Lignin is a promising feedstock in sustainable formulations for agrochemicals not only because of its biodegradability but also because the biopolymer occurs naturally in the cell wall of plants and therefore is renewable and abundant. We used different lignin sulfonates to prepare stable aqueous dispersions of lignin nanocarriers loaded with agrochemicals by interfacial cross-linking in a direct miniemulsion. Despite the differences in structure and functionality, different lignin sulfonates were successfully methacrylated and degrees of methacrylation (>70%) were achieved. The resulting methacrylated lignin sulfonates were water-soluble and exhibited interfacial activity; they were used as reactive surfactants to stabilize oil droplets (cyclohexane or olive or rapeseed oil) loaded with a dithiol cross-linker [EDBET, 2,2′-(ethylenedioxy)bis(ethylthiol)] and a hydrophobic cargo (the fluorescent dye 1,3,5,7-tetramethyl-8-phenyl-4,4-difluoroboradiazaindacene or the commercial fungicides prothioconazole and pyraclostrobin). After the addition of a water-soluble base, the thia-Michael addition was initiated at the droplet interface and produced lignin sulfonate nanocarriers with a core–shell structure within oily core and a cross-linked shell. Nanocarriers with diameters of ca. 200–300 nm were prepared; encapsulation efficiencies between 65 and 90% were achieved depending on the cargo. When the amount of the cross-linker was varied, the resulting lignin nanocarriers allowed a controlled release of loaded cargo by diffusion over a period of several days. The strategy proves the potential of lignin sulfonates as a feedstock for delivery systems for advanced plant protection.

Unravelling the Hydration Barrier of Lignin Oleate Nanoparticles for Acid‐ and Base‐Catalyzed Functionalization in Dispersion State

“…The unequivocally higher stability of OLNPs in acidic and basic media in contrast to regular LNPs envisions the possibility of programming their stability on‐demand by tuning the DE, which would be useful for active loading and release of pesticides for advanced plant protection. [53] We attribute this significant increase in the stability of OLNPs to the hydration barrier caused by the presence of oleate chains resting on the surfaces of OLNPs. Under acidic and basic conditions, these hydrophobic chains would act as an external hydrophobic membrane, hindering access and thus protonation of carboxylic acid groups and ionization of phenolic hydroxyl groups.…”

Unravelling the Hydration Barrier of Lignin Oleate Nanoparticles for Acid‐ and Base‐Catalyzed Functionalization in Dispersion State

“…The unequivocally higher stability of OLNPs in acidic and basic media in contrast to regular LNPs envisions the possibility of programming their stability on‐demand by tuning the DE, which would be useful for active loading and release of pesticides for advanced plant protection [53] . We attribute this significant increase in the stability of OLNPs to the hydration barrier caused by the presence of oleate chains resting on the surfaces of OLNPs.…”

Recent Advances on Lignocellulosic-Based Nanopesticides for Agricultural Applications

“…Such nanoparticles prevented the formation of hyphae in wood as well as increased the strength of the composite (Gao et al, 2021b). Additionally, lignin sulfonate-based nanocarriers containing hemicellulose residues showed potential for controlled delivery of agrochemicals such as the fungicides pyraclostrobin or prothioconazole (Beckers et al, 2020b). In addition, xylan-based nanoparticles are advantageous for their biocompatibility, biodegradability, and low-cost biological material (Beckers et al, 2020b).…”

“…Additionally, lignin sulfonate-based nanocarriers containing hemicellulose residues showed potential for controlled delivery of agrochemicals such as the fungicides pyraclostrobin or prothioconazole (Beckers et al, 2020b). In addition, xylan-based nanoparticles are advantageous for their biocompatibility, biodegradability, and low-cost biological material (Beckers et al, 2020b). Recently, lignin-xylan and arabinoxylan nanoparticles were also reported as an enzymatic-responsive for pesticides release (Jiang et al, 2020) (Table 1) as well as a gene delivery system for CRISR-Cas9 DNA (Sarker et al, 2020), respectively.…”