Inverse Opal Photonic Hydrogels for Blue-Edge Slow Photon-Enhanced Photodynamic Antibacterial Therapy

Photodynamic therapy is promising for combating bacteria by reactive oxygen species. However, the therapeutic efficiency of photodynamic antibacterial therapy (PDAT) is largely hindered by limited photon absorption and the low quantum yield of photosensitizers. Herein, a novel light-harvesting platform is designed by decorating photosensitizer chlorine e6 (Ce6) into an inverse opal photonic hydrogel (Ce6/IOPG) framework for efficient light utilization to enhance PDAT. It is shown that the generating efficiency of singlet oxygen (¹O₂) can be tuned by the relative positions of the photonic bandgap (PBG) of IOPG and the absorption band of Ce6. The coupling of the slow photon effect with the efficient dispersion of Ce6 allows for a maximum generation of ¹O₂ of approximately 69.5-fold and markedly enhances PDAT activity upon low light irradiation when the blue edge of PBG overlaps with the absorption band of Ce6. Particularly, slow photons at the blue edge show advantages in improving ¹O₂ generation compared to those at the red edge. The variation in ¹O₂ generation by altering the incident angle of light provides direct evidence for the slow photon effect in Ce6/IOPG. This work provides insights into blue-edge slow photons in photodynamic enhancement and offers an advisable design principle for efficient antibacterial therapy.