Fabrication and characterization of lignin-xylan hybrid nanospheres as pesticide carriers with enzyme-mediated release property

Lignin nanospheres (LNPs) is an emerging high-value material platform to realize lignin valorization. The modification or introduction of new functions to LNPs are of great significance to expand its downstream applications. This work evaluated the technical feasibility of preparation of lignin-xylan hybrid nanospheres (LXNPs) through simple solution based self-assembly process, with the goal of achieving the application as pesticide carriers for enzyme-mediated controlled release. Hybrid LXNPs with various weigh ratios (lignin to xylan, 3:1, 1:1, 1:3) were obtained using deep eutectic solvent extracted condensed lignin and water insoluble xylan fragments, which exhibited nanosphere size of 166~210 nm with considerable stability at pH 4~10. LXNPs with lignin to xylan ratios of 3:1 and 1:1 showed well-defined core-shell structure with enriched hydroxyl groups in the surface. It was proposed lignin could anchor xylan fragments through van der Waals force and hydrophobic interactions between lignin phenylpropanes and xylan molecular backbones thus facilitating the self-assembly process to form this specific spherical structure. The resulting hydrophobic LXNPs core enabled the facile encapsulation of biological pesticide avermectin (AVM) with 57.9~67.0% efficiency using one-pot synthesis. When these AVM-encapsulated LXNPs were subjected to enzymatic hydrolysis using xylanase, considerable AVM release of 44.8~55.1% was achieved after 16 h, in comparison to the only 4.1% release for those without xylanase. This work showed the high promise of fabricating hybrid LXNPs through self-assembly process, and also provided a universal nanosphere carrier for drug encapsulation and subsequent enzyme-mediated controlled release.