Esterified Lignin Nanoparticles for Targeted Chemical Delivery in Plant Protection

There is a growing demand for biobased functional materials that can ensure targeted pesticide delivery and minimize active ingredient loss in the agricultural sector. In this work, we demonstrated the use of esterified lignin nanoparticles (ELNPs) as carriers and controlled-release agents of hydrophobic compounds. Curcumin was selected as a hydrophobic model compound and was incorporated during ELNP fabrication with entrapment efficiencies exceeding 95%. ELNPs presented a sustained release of curcumin over 60 days in an oil medium, with a tunable release rate dependent on the lignin-to-curcumin mass ratio. The ELNPs showed a strong adhesion interaction with the hydrophobic wax surface. Quartz crystal microbalance with dissipation monitoring (QCM-D) and atomic force microscopy (AFM) analysis suggested that the ELNPs permeated into the wax layer, potentially preventing pesticide loss due to runoff or rainwater leaching. Rapidly decreasing contact angles between a droplet containing an aqueous dispersion of the ELNPs and a fresh leaf surface provided further evidence of a favorable interaction between the two. Overall, our results portray ELNPs as promising biobased nanoparticulate systems for pesticide delivery to hydrophobic plant surfaces.