Perfluorocarbon Nanocapsules Improve Hypoxic Microenvironment for the Tumor Ultrasound Diagnosis and Photodynamic Therapy

Amelioration of hypoxia is an important factor increasing the effects of anti-tumor therapies. In the present experiments, nanocapsules of poly(lactide-co-glycolide)-poly(ethylene glycol)/perfluorooctyl bromide (PFOB)/photosensitizers (IR780) have been developed to increase oxygen concentration inside the tumor and improve the outcome of photodynamic therapy (PDT). PFOB has high oxygen solubility, and IR780 is a photosensitizer particularly suited for a highly effective photodynamic therapy under the 808-nm laser irradiation. Thus, PFOB provides sufficient oxygen for the reaction with the photosensitizer, producing more singlet oxygen to induce cell apoptosis. The photodynamic effect of nanocapsules was confirmed to be enhanced after addition of PFOB through simulation experiments in vitro in the hypoxic microenvironment. The results have demonstrated that due to the addition of PFOB the nanocapsules can provide a contrast-enhanced ultrasound diagnosis and ensure more notable inhibition of the growth of lung tumors following the 808 nm laser irradiation. Furthermore, the nanocapsules allowed the photosensitizers to achieve sufficient therapeutic potential, which was optimal under the conditions of modest hypoxia with about 5% oxygen concentration.