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 (1O2) 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 O2 to 1O2. 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.