Esterified lignin nanoparticles for targeted pesticide delivery to plant leaves

As the world population continues it rapid increase, a strained food security demands intensified agricultural practices and as a consequence an increased use of chemicals like pesticides. But the majority of applied pesticides never reaches its target, and are instead lost due to factors like UV-radiation, rolling off or rain water leaching. Thus, the field of nanopesticides have gained a lot of interest as a solution to this problem, thanks to the tunability of for example surface chemistry and size. In the present work, esterified kraft lignin was used to entrap a hydrophobic cargo through the formation of esterified lignin nanoparticles. The system showed a high entrapment efficiency and a sustained release for 60 days in an oil medium. Additionally, the nanoparticles interaction with a model surface of extracted corn leaf wax and fresh corn leaves was evaluated. The interaction with the model surface suggested that the esterified lignin nanoparticles permeated through the wax, allowing for a decrease in losses due to for example rain water leaching. Further investigation of the particle interaction with a real corn leaf presented a rapidly decreasing contact angle, suggesting a favourable interaction between the particles and the surface waxes of the leaf. The obtained results suggest that this could be a simple and biobased system, facilitating a reduction of pesticide loss while allowing for effective plant protection.