pH-Responsive Oxygen and Hydrogen Peroxide Self-Supplying Nanosystem for Photodynamic and Chemodynamic Therapy of Wound Infection.

The combination of photodynamic therapy (PDT) and chemodynamic therapy (CDT) has been continuously explored in the antibacterial aspect and has achieved more effective antibacterial effect than a single therapy. We design a pH-responsive O2 and H2O2 self-supplying zeolitic imidazolate framework-67 (ZIF-67) nanosystem for PDT/CDT of wound infection. Under the acidic inflammatory conditions, ZIF-67 can degrade to produce Co2+ and release CaO2 and graphene quantum dots (GQDs). The exposed CaO2 reacted with water to generate H2O2 and O2. The self-supplied O2 alleviates hypoxia at the site of inflammation and enhances external light-initiated GQD-mediated PDT, while H2O2 was catalyzed by endogenous Co2+ to produce hydroxyl radicals for Co2+-triggered CDT. In vitro and in vivo experiments confirm that CaO2/GQDs@ZIF-67 has a combined PDT/CDT effect. The antibacterial mechanism indicates that bacteria post-treated with CaO2/GQDs@ZIF-67 may be sterilized by reactive oxygen species-mediated oxidative stress and the leakage of bacterial contents. The experiments also find that CaO2/GQDs@ZIF-67 may activate the immune response and enhance the therapeutic effect by activating the cyclic GMP-AMP synthase-stimulator of interferon genes signaling pathway.