Enhancement of photodynamic therapy for pneumonia treatment: in vitro studies

The rise of antimicrobial resistance demands alternative therapies targeting multiple molecular sites, such as Antimicrobial Photodynamic Therapy (aPDT). By inactivating microorganisms through oxidative stress, aPDT reduces the risk of resistance development. Our research focuses on the efficacy of aPDT against pneumonia-causing pathogens, a leading cause of global mortality. While in vitro studies have demonstrated the safety and effectiveness of aPDT for Streptococcus pneumoniae and the successful delivery of photosensitizers (PS) with infrared light in animal models, in vivo applications face significant challenges due to lung surfactant (LS). LS traps PS, limiting its efficiency. This study investigated strategies to enhance PS distribution within LS. The combination of indocyanine green (ICG) with the copolymer Gantrez™ AN-139 proved most effective, achieving complete microbial load reduction without toxicity to human lung cells. These findings highlight its potential as a strategy to overcome LS barriers and advance aPDT toward successful in vivo applications.