Chlorophyllin as a photosensitizer in photodynamic antimicrobial materials

Self-disinfecting materials that are both safe and scalable for production are increasingly in demand, particularly in healthcare settings where they can be used to combat hospital-acquired infections (HAIs). Here, we employed the natural food colorant chlorophyllin (E140ii) as a photosensitizer to prepare photodynamic antimicrobial materials through both chemical conjugation and electrospinning, resulting in chlorophyllin-grafted cotton fabric (Chl-fabric) and chlorophyllin-embedded polyacrylonitrile nanofibers (Chl-NF), respectively. The materials were characterized by a number of physical methods, as was their ability to generate singlet oxygen upon visible light illumination. The best results with Chl-fabric yielded 99.998% inactivation of vancomycin-resistant E. faecium and 99.994% of methicillin-resistant S. aureus after 60 min visible light illumination (400–700 nm, 80 ± 5 mW/cm²), whereas Chl-NF inactivated both bacteria by 99.9999%. Feline calicivirus was also photodynamically susceptible, with 99.8% inactivation by both materials. Gram-negative Klebsiella pneumoniae was not initially susceptible to photodynamic inactivation by Chl-NF, however addition of the photothermal agent MoS₂ fully inactivated (99.9999%) this pathogen under NIR illumination, indicative of synergistic photothermal and photodynamic activities. These findings suggest that chlorophyllin can be used in photodynamic antimicrobial materials against drug-resistant Gram-positive bacteria, and that its efficacy can be synergistically amplified in the presence of a photothermal agent against Gram-negative pathogens.