Advances of research on oxygen-enhancing nano-delivery system for photodynamic therapy

Photodynamic therapy, a new type of non-invasive treatment, is based on the principle that the photosensitizer excited by laser can transfer energy to oxygen, which generates cytotoxic singlet oxygen and thus induce tumor cell apoptosis or necrosis. As an oxygen-dependent therapy, the antitumor effect of photodynamic therapy is obviously limited by hypoxia environment of solid tumor tissue. Therefore, reversing and improving the hypoxia of tumor tissue can significantly enhance the efficacy of photodynamic therapy. This review focuses on the progress of tumor oxygenation strategy mediated by nano-delivery system, including direct oxygen delivery strategies, catalytic oxygen production strategies, responsive material in situ oxygen supply strategies and microorganism oxygen supply strategies, aiming to improve the antitumor effect of photodynamic therapy. It provides new ideas and new approaches for further study of oxygen-enchancing nano-delivery system for photodynamic therapy.