High-efficiency platinum-carbon nanozyme for photodynamic and catalytic synergistic tumor therapy

Photodynamic therapy (PDT) is an effective approach for tumor treatment, which converts oxygen into reactive oxygen species (ROS) through light irradiation upon a photosensitizer. Due to the low instability of most current photosensitizers, nanocarriers for loading and delivering photosensitizers were specifically needed to be developed. However, most nanocarriers, such as polymer-based, lipid-based vehicles, only act as a carrier, without antitumor activity. Thus, development of suitable nanocarriers for photosensitizers with integrating multi -antitumor functions will improve the efficiency of PDT. Here, we reported two different kinds of Pt/carbon (Pt/C) nanozymes as the nanocarriers for chlorin e6 (Ce6) loading. Besides the PDT based on Ce6, Pt/C nanozymes could mimic the activities of peroxidase and oxidase to transfer H2O2 and O2 in tumor sites to ROS respectively, further killing tumor. By comparing the distribution of Pt nanoparticles inside or outside the carbon spheres, we found that it exhibited higher enzyme-mimicking and antitumor activity when the Pt was loaded outside the carbon shell. Cellular and animal studies demonstrated that the efficient tumor destruction was achieved through the combination of PDT and nanozyme-based catalytic therapy. These results implied that the intrinsic enzyme-like activity of nanozymes and PDT can be synergized for efficient tumor treatment, providing a proof of-concept of tumor photodynamic-catalytic therapy.