Sustainable Strategies in the Synthesis of Lignin Nanoparticles for Actives Release: a Comparison.

The preparation of nanoparticles represents a powerful tool for lignin valorization, as it combines easy methodologies with high application potential. Different synthetic strategies and various lignin sources have been employed in the process. However, the great variability in the lignin structure prevents from a direct comparison of the so far reported lignin nanoparticles (LNPs), especially as regards their physicochemical and functional properties. To this purpose, two green protocols, i.e. solvent-antisolvent and hydrotropic, have been optimized and used to generate LNPs from the same softwood kraft lignin. The nanomaterials have been fully characterized to extrapolate structure/property relationships and reveal any differences in the mechanism of self-assembly. Furthermore, tests on methylene blue entrapment capacity and release behavior at two different pHs (2.0 and 7.4) evidenced a clear dependence on the LNPs characteristics, thus on the strategy adopted for their production.