BODIPY−Bimetallic Nanoconjugate-Doped Lignin Nanogel Coated Gauze for Photoinhibition of Pathogens

The prompt and growing emergence of antimicrobial and infection-resistant wound dressings demands the development of alternative non-antibiotic therapeutic materials. Herein, we present a green, sustainable, and scalable antimicrobial wound dressing based on 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene/boron-dipyrromethene (BODIPY) bimetallic nanoconjugate-doped lignin nanogels (CB@BM-LNC NG) coated on cotton gauze. Conjugatable chlorinated BODIPY (CB) with ester functionality was synthesized in good yield and covalently linked to lignin-derived bimetallic nanocomplexes via diimide coupling. The resulting nanoconjugates exhibited stable formulation and enhanced singlet-oxygen generation. These nanoconjugates were subsequently incorporated into the lignin nanogel to create a pH-responsive, controlled, and sustained drug release. The composite lignin nanogel exhibited synergistic and catalytic photodynamic antimicrobial efficiency against Escherichia coli, Staphylococcus aureus, and Candida albicans (IC50 = 3−5 μM) under green light. CB@BM-LNC NG effectively eliminates microbes via cell membrane disruption, as confirmed by fluorescence and SEM imaging. Additionally, the photodynamic lignin nanogel coated onto medical gauze indicated rapid light-triggered broad-spectrum pathogen inhibition. An environmentally friendly, antibiotic-free wound dressing could be a potential lignin-based nanomaterial for next-generation antimicrobial therapies and infection-resistant healthcare materials.