Near-Infrared Light-Triggered Synergistic Phototherapy for Antimicrobial Therapy

Phototherapy has great advantages in combating bacterial infection, in particular, those therapies mediated by near-infrared light. To advance phototherapy for bacterial infections, a positively charged conjugated polymer (termed PTDBD) with near-infrared light-triggered activity is employed for antimicrobial therapy in this paper. The quaternary ammonium groups in side chains of PTDBD can benefit from the interaction between the polymer and negatively charged membrane of bacteria, and such a structure can also induce the aggregation of bacteria to improve local antibacterial efficiency. Upon single near-infrared light irradiation, simultaneous reactive oxygen species (ROS) and heat generated by the polymer PTDBD can effectively kill bacteria at low treatment concentration (40 μg·mL-1) and low light density (1.0 W·cm-2) toward both Gram-positive bacteria (Staphylococcus aureus) and Gram-negative bacteria (ampicillin-resistant Escherichia coli TOP 10). For fungi (Candida albicans), a higher treatment concentration of PTDBD is needed to kill at the same light density. Finally, the dual phototherapy is also employed to treat the bacteria-infected wound of mice with no tissue damage observed. The integration of positive charges, ROS, and heat provides a highly efficient and broad spectrum antimicrobial strategy for further treatment of bacterial infections in vivo.