LIFU (Low-Intensity Focused Ultrasound) Activated Tumor-Starvation/Oxidative-Stress Combined Therapy for Treating Retinoblastoma.

PURPOSE: To overcome the limitations of traditional therapies in treating retinoblastoma, like low efficiency, systematic toxicity and poor biocompatibility. MATERIALS AND METHODS: PPFG (PLGA-PFH-Fe(3)O(4)-GOx) nanoparticles were synthesized by ultrasound double emulsification method and characterized by dynamic laser scattering, ultraviolet spectrometry, confocal laser scanning microscopy (CLSM), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Phase transition by low-intensity focused ultrasound (LIFU) was observed by microscope and ultrasound imaging. Cellular uptake was compared between Y79 and HUVEC cells. ROS production was detected by 2',7'-dichlorofluorescin diacetate (DCFH-DA). Cell apoptosis was detected by flow cytometry. In vivo therapeutic effects were verified by tumor volume, HE staining, TUNEL and PCNA staining. The in vivo bio-safety was detected by serum biochemistry. RESULTS: PPFG NPs possesses good stability, biocompatibility and tumor-preferred uptake, with a core-shell spherical structure and an average size of 255.6nm which increases to over 100μm under LIFU irradiation. LIFU was utilized as a stimuli, by which PPFG NPs undergoes a sequential reaction starting with phase transition of PFH causing the release of the oxygen carried by PFH and GOx/SPIO carried by PPFG NPs, followed by the supplemented oxygen facilitating the enzymatic activity of glucose consumption by GOx in tumor cells (tumor starvation), the H(2)O(2) produced during the enzymatic activity can further participate in SPIO NPs-mediated Fenton reaction (CDT), generating massive ROS. The continuously generated ROS together with the cut down of tumor nutrients by GOx effectively inhibited the progression of tumors, and synergistically enhanced ROS production together with tumor starvation promoted cell apoptosis and ultimately kills the tumour cells. No off-site injuries was detected in other major organs. CONCLUSION: In this study, PPFG nanoparticles were synthesized to conduct LIFU-triggered combinational therapy on the basis of the cascade reaction among PFH, GOx and SPIO to treat retinoblastoma in vitro/vivo. It showed great potentials in combating retinoblastoma.