Enhanced antibiofilm photodynamic therapy: Leveraging the slow photon effect for maximized efficacy with minimal photosensitizer and light doses

The persistent and recurrent nature of biofilm infections, coupled with their increased resistance to antibiotics, poses a significant health risk. Photodynamic therapy has emerged as a promising strategy against biofilms, and it is crucial to fully harness the optimal potential of photosensitizers for generating reactive oxygen species (ROS) in order to prevent the development of resistance through insufficient ROS induction. The present study describes the fabrication of a photodynamic platform through the conjugation of photosensitizer chlorine e6 (Ce6) into inverse opal photonic crystal (IOPC) with a matching photonic band edge. The resulting slow photon effect of IOPC improves the light-harvesting capacity of Ce6 and ensures a 370% enhancement in the production of high levels of ROS at low Ce6 dosage (nanomolar levels) and light intensity (3 mW cm−2). In vitro experiments demonstrate that IOPC enhances the photodynamic antibiofilm efficacy of Ce6 by an impressive 375%. Furthermore, in vivo experiments confirm that IOPC expedites wound healing in mice infected with biofilm through photodynamic treatment. This work provides valuable insights into the phenomenon of slow photon effect in enhancing photodynamic therapy and presents a recommended design principle for achieving efficient antibiofilm treatment.