Catechyl lignin enhances self-assembly for Pickering emulsion stabilization and controlled-release application.

The structure of lignin significantly affects its self-assembly ability into lignin nanoparticles (LNPs) and their properties for specific applications. Herein, several lignin oligomers with distinctive chemical structures were extracted from typical biomasses and self-assembled into LNPs, which were further used to stabilize the Pickering emulsion. The linearly arranged catechyl unit and the abundant phenolic hydroxyl groups in the castor seed coat-derived lignin oligomers would promote their π-π stacking and hydrogen bonding interactions for self-assembly. Associated with further fractionation of the catechyl lignin, the hydrophilic part with a large molecular weight was separated and self-assembled into small and uniform LNPs. The catechyl unit in catechyl lignin self-assembled LNPs endowed the high hydrophilicity of the LNP surface with a rich negative charge. The uniform LNPs stabilized the Pickering emulsion with smaller vacuoles, which showed high stability for at least 15 days. Subsequently, the LNP-stabilized Pickering emulsion was applied for curcumin encapsulation, improving its storage and controllable release. This study may contribute to the application of curcumin in food and drug formulations, increase the utilization efficiency of pharmaceutical molecules and reduce their usages, creating economic benefits and alleviating environmental issues.