Porphyrin Containing Polymersomes with Enhanced ROS Generation Efficiency: In Vitro Evaluation

Porphyrins are molecules possessing unique photophysical properties making them suitable for application in photodynamic therapy. The incorporation of porphyrins into natural or synthetic nano‐assemblies such as polymersomes is a strategy to improve and prolong their therapeutic capacities and to overcome their limitations as therapeutic and diagnostic agents. Here, 5,10,15,20‐tetrakis(1‐(6‐ethoxy‐6‐oxohexyl)‐4‐pyridin‐1‐io)‐21H,23H‐porphyrin tetrabromide porphyrin is inserted into polymersomes in order to demonstrate that the encapsulation enhances its ability to generate highly reactive singlet oxygen (1O2) upon irradiation in vitro. The photoactivation of the free and polymersome‐encapsulated porphyrin is evaluated by electron spin resonance and cell viability assays on three different mammalian cell lines. The results indicate that by encapsulating the porphyrin, a controlled ROS delivery within the cells is achieved, at the same time avoiding side effects such as dark toxicity, non‐specific porphyrin release and over time decreased activity in vitro. This work focuses on showing a not‐toxic model system for modern therapeutic nanomedicine, which works under mild irradiation and dosage conditions. ROS generating TPyCP porphyrin is incorporated into polymersomes and its ability to cause controlled oxidative stress to mammalian is studied. The TPyCP containing polymersomes show efficient ROS delivery into HeLa, HEK and HepG2 cells. TPyCP's encapsulation into polymersomes improves the cellular uptake, preserves the ROS delivery upon irradiation and minimizes the dark toxicity of the free compound.