Investigation of PPIX-Lipo-MnO 2 to enhance photodynamic therapy by improving tumor hypoxia.

The efficacy of photodynamic therapy (PDT) is reduced in the context of hypoxic environments. This is problematic, considering that hypoxia is exhibited in the vast majority of malignant tumors. Thus, increasing the concentration of oxygen in malignant tumors improves PDT treatment outcomes. Studies show that MnO2 nanoparticles can produce oxygen when it reacts with endogenous H2O2. Herein, we encapsulated Protoporphyrin DC (PPIX) in the liposome bilayer (PPDC-Lipo), which was then coated with MnO2 nanoparticles to construct PPIX-Lipo-MnO2 (PPDC-Lipo-M) in order to enhance PDT efficacy under tumor hypoxia. The PDT results show that PPDC-Lipo-M was more cytotoxic to breast cancer cells than PPDC-Lipo while under hypoxic conditions, indicating that the production of oxygen gas in hypoxic conditions improved treatment outcomes. Upon encapsulating PPDC into the liposome, the aqueous solubility of PPDC significantly improved. Consequently, the cellular uptake of both PPIX-Lipo and PPDC-Lipo-M also increased significantly compared to that of bare PPDC. Overall, PPDC-Lipo-M has the capacity to act as a therapeutic agent that relieves hypoxia and hence improve PDT efficacy.