Gallate-oriented surface engineering of lignin nanoparticles for enhanced antibacterial activity.

In combating bacterial infections, antibacterial nanomaterials offer a non-pharmacological alternative to conventional antibiotics. Biomass-derived lignin exhibits intrinsic antibacterial activity from polyphenolic motifs and can readily self-assemble into nanostructures due to its amphiphilicity. However, the formation of lignin nanoparticles (LigNPs) is governed by a delicate balance of noncovalent interactions, making assembly outcomes highly dependent on lignin source and fractionation process and thereby limiting precise control over the surface chemistry and functional-group presentation. Here we have developed a gallate-oriented surface engineering strategy that combines boronated lignin nanoparticles (BLigNPs) core with gallate derivatives (GDs) corona, enabling tunable surface chemistry and modulating their bactericidal activity to preferentially target Gram-negative or Gram-positive bacteria. Through spatially grafting redox-active pyrogallol moieties in a tannic acid (TA) corona, BLigNP-TA exhibited the highest antibacterial activity against S. aureus. In contrast, owing to the balanced hydrophilicity/hydrophobicity in a propyl gallate (PG) corona, BLigNP-PG showed the highest antibacterial activity against E. coli. Consistent with this interpretation, BLigNP-PG exhibited enhanced envelope association and permeabilization in both Gram-negative and Gram-positive bacteria, supporting a contact-associated antibacterial action via a multimodal and multitarget mechanism. Beyond planktonic bacteria, both corona designs enhance the nanoparticle association with biofilm-relevant interfaces and facilitate the nanoparticle transport within biofilms. Notably, BLigNP-PG exhibited good biocompatibility with fibroblasts and negligible toxicity in zebrafish, underpinning its translational potential as an antibacterial nanomaterial with high selectivity toward bacteria over mammalian cells.