Research progress in metronomic photodynamic therapy

Metronomic photodynamic therapy (mPDT) is a new type of photodynamic therapy (PDT) that has received much attention in recent years. It has a similar therapeutic mechanism to traditional PDT, i.e. the photosensitizer is irradiated by visible light irradiation with a specific wavelength, and tissue oxygen photochemical reactions produce cytotoxic reactive oxygen species (ROS) that selectively kill rapidly proliferating tumor cells. Unlike traditional PDT, the photosensitizer and light in mPDT are continuously transmitted at a low time and at a low rate, and the specificity of tumor treatment is enhanced by apoptosis. In this paper, the current researches on the in vitro and in vivo effects and mechanisms of mPDT, as well as the research status of photosensitizers and light sources for in vivo research, were reviewed, with a view to understanding the existing mPDT technology and providing reference for the further studies. This review paper can provide a basic for promoting the clinical research and application of mPDT. Key words: Metronomic photodynamic therapy; Photosensitizers; Light sources; Brain tumor; 5-aminolevulinic acid