Research progress of nanomaterial-mediated photodynamic therapy in tumor treatment

Photodynamic therapy (PDT) is a new approach to destroy tumor over past decades due to its high selectivity and minimal invasiveness. Photosensitizers (PSs), plenty of oxygen, and special wavelengths of light irradiation are three indispensable basic elements in the PDT therapeutic procedure. Upon exposed to light irradiation, PSs utilized surround oxygen to produce poisonous reactive oxygen species (ROS) to kill cancer cells through apoptosis or necrosis. PDT cased cancer cells damage highly dependent on tissue oxygen concentration and DNA self-repairing inhibition. Therefore, altering ROS homeostasis in cancer cells can be exploited for tumor therapeutic. Furthermore, PDT as the highly selective therapy approach can directly ablate solid tumor at primary sites. Meanwhile, it can induce immunogenic cell death by release damage-associate molecular patterns and tumor-associated antigens to activate immune response for inhibit cancer recurrence and metastasis. However, PDT was seriously hampered due to the poor drug penetration depth and unfavorable biodistribution of PSs at the lesion tissues. As the development of nanomaterial, nanotechology-based PDT have made a huge revolution in cancer therapeutic, which can effectively overcome these drawbacks and ameliorate the complex tumor microenvironment to enhance PDT effects. In general, the size of nanoparticles between 50 and 100 nm can prolong blood circulation time and efficiently tumor accumulation through enhanced permeability and retention (EPR) effects. Once inside the tumor tissues, they should be small enough to enhance penetration. Given this, we summarize the advances of PDT in tumor therapeutic.