Tumor microenvironment sensitization via dual-catalysis of carbon-based nanoenzyme for enhanced photodynamic therapy

Photodynamic therapy (PDT) is limited in tumor therapy due to the mature antioxidant barrier of tumor microenvironment (TME) and phototoxicity/easy-degradation characteristics of photosensitizers. Therefore, we prepared Cu²⁺-doped hollow carbon nanoparticles (CHC) to protect the loaded photosensitizers and sensitize TME by glutathione-depletion and peroxidase (POD)-like activity for enhanced PDT. CHC significantly increased the maximum speed of POD-like reaction (V_m) of 8.4 times. By coating with hyaluronic acid (HA), the active sites on CHC were temporarily masked with low catalytic property, and restored in response to the overexpressed hyaluronidase in TME. Meanwhile, due to the excellent photothermal conversion efficiency (32.5 %) and hollow structure of CHC, the loaded photosensitizers were well protected from sunlight activation-induced unwanted phototoxicity and rapid degradation under the near-infrared light irradiation. In-vivo anti-tumor experiments demonstrated that the combination of photothermal-photodynamic effect achieved the best anti-tumor effect (tumor inhibition rate at 87.8 %) compared with any monotherapy. In addition, the combination of photothermal and photodynamic effect could efficiently suppress the cell migration, manifesting the reduced number of lung metastasized nodules by 74 %. This work provides an integrated platform for photosensitizers protection and TME sensitization for enhanced PDT.