Near-infrared Light-excited Self-supplying Oxygen System For Photodynamic Therapy Of Hypoxic Tumors

Photodynamic therapy?PDT?is a new technique for disease diagnosis and treatment by photodynamic effect,compared with traditional radiotherapy and chemotherapy,photodynamic therapy has many advantages,such as good selectivity,low toxicity,less trauma and less resistance.Its basic elements are oxygen,photosensitizer and light,in other words,photodynamic therapy must rely on enough oxygen.However,hypoxia is an inherent feature of the majority of solid tumors,which can increase the resistance of tumor cells to radiotherapy and chemotherapy,promote tumor angiogenesis and lead to poor prognosis.Therefore,how to improve the efficacy of photodynamic therapy in the anoxic area of tumors so as to eliminate tumors completely has become a difficult problem recognized by the international medical community.It is very important to improve the partial pressure of oxygen in the area of anoxic tumor to improve the efficiency of PDT for the patients with hypoxic tumor.In order to solve this problem,many methods have been derived in recent years,such as using inorganic materials to catalyze the endogenous H₂O₂ to generate oxygen,cutting off the oxygen consumption pathway of cells,and using materials with strong oxygen-dissolving capacity to carry oxygen into tumors.However,the oxygen generation effect of these methods will be limited by the endogenous H₂O₂ and the material concentration,resulting in unsatisfactory photodynamic therapy.Cyanobacteria,as the earliest photosynthetic oxygen-generating organisms on the planet,can utilize water as an electron donor and use sunlight to reduce CO₂ to organic carbon compounds,which continuously releases oxygen.Inspired by this,we will conjugate the photosensitizer-upconversion nanoparticles with cyanobacteria that possesses self-supplying oxygen and phototactic capacity.The improved PDT efficiency for hypoxic tumor will be achieved in favor of in situ oxygen production of cyanobacteria.This proof of concept is of great significance and may open the door to a new generation of carrier systems in the field of hypoxia-targeted drug transport platform.