Acetylated lignin nanoparticles as a possible vehicle for photosensitizing molecules.

Lignins are underused and abundant bio-sourced polymers with various potential applications. An attractive one is the development of nanoparticles for bioactive compound delivery. Here, we optimized the synthesis of hydrodispersible nanoparticles of acetylated lignin by comparing different lignin sources, degrees of acetylation and preparation methods. The formation of acetylated lignin nanoparticles in various solvents was probed by both experiments and, for the first time, a molecular dynamics simulation. We showed that dialysis is more suitable to obtain these nanoparticles than anti-solvent addition. The encapsulation of hydrophobic photosensitizing porphyrin in these nanoparticles was also demonstrated and rationalized at the molecular level, together with experiments, docking and molecular dynamics simulations. As acetylated lignin has been demonstrated to exhibit photosensitizing activity, the encapsulation of bioactive compounds in lignin nanoparticles opens the doors to a broad range of potential applications.