Porphyrin-conjugated lignin p-n heterojunction as an effective and biocompatible photosensitizer for antibacterial applications

This work explores the potential of porphyrin-grafted lignin nanoparticles (TCPP- g -AL-NPs) as a novel, effective, and biocompatible photosensitizer for antibacterial applications. Lignin acted as a sustainable framework, enhancing water-compatibility and single oxygen ( 1 O 2 ) generation of porphyrin. The mechanism study revealed the successful formation of a p-n heterojunction between lignin and porphyrin, which promoted the charge separation and the photocatalytic process of O 2 to 1 O 2 . In vitro antibacterial assessments demonstrated the efficacy of TCPP- g -AL-NPs in eradicating both Gram-negative ( E. coli ) and Gram-positive ( S. aureus ) bacteria under blue LED light irradiation. The observed lower antibacterial effectiveness against E. coli compared to S. aureus could be attributed to the thicker cell membrane of Gram-negative bacteria. Additionally, TCPP- g -AL-NPs exhibited no cytotoxicity towards mouse fibroblast cells (L929). This study presents a straightforward and promising approach for developing lignin-based photosensitizers for photodynamic therapy.