Study On The Radiosensitivity Of Gold Nanoparticles For Glioblastoma

ObjectiveOwing to high Z metal, Gold nanoparticles(Au NPs) can increase the efficiency in generating secondary electrons and have a strong photoeletric absorption under gamma ray or X-ray irradiation. Therefore, Au NPs can be used as a radiotherapy sensitization agent to increase the destruction role on tumor tissue by ionizing radiation, aiming to improve the curative effect of radiotherapy. More importantly, as a promising radiosensitizer, Au NPs have excellent properties such as easy preparation, great chemical stability, low toxicity. In this study, we synthesize two types of Au NPs to examine the radiosensitization in U87 glioblastoma cell line by measurement of colony formation assay, damage of DNA, and cell apoptosis in vitro. Meanwhile, we investigate the enhancement of radiation therapy on in vivo tumor modals. Our study would provide reliable experimental basis for Au NPs as a radiotherapy sensitization agent for potential clinical applications.MethodsWe use chemical reduction method to prepare Au NPs functionalized with different polymers including BSA and PLVs. The obtained Au NPs are characterized by Nano ZS Zetasizer, Cary 50 spectrophotometer, and a transmission electron microscopy(TEM). The safe concentration of two kinds of Au NPs are determined by MTT assay. In addition, transmission electron microscopy and confocal laser scanning microscopy are carried out to measure the in vitro behaviors. Colony assay was performed to compare the cell survival fractions post-radiation between the control and treated group. Immunofluoresence assay and flow cytometry are carried out to quantify γ-H2 AX foci in 0.5 h, 2 h and 4 h post-radiation on U87 cells, and the cells apoptosis in 48 h post-radiation, respectively. The ICP-AES was performed to determine blood circulation and tissue distribution at 2 h and24 h after intravenous administration of Au NPs. The U87 glioblastoma tumors are generated by subcutaneous injection of 2×106 cells suspended in 50 μL PBS into the dorsal region near the thigh. The mice are intravenous injected BSA-Au NPs or PBS as control when the diameter of tumor is approximately 0.8-1 cm. Subsequently, the mice weie irradiated by X-ray. The enhancement of radiation therapy of Au NPs was evaluated by the volume and weight change of tumors after treatment. The toxicity effect of Au NPs was investigated by using histological analysis and the weight change.Results1 Synthesis of BSA-Au NPs and Au-PLVs with diameters of 28 nm and 90 nm, respectively.2 In virto:(1) MTT assay indicated that BSA-Au NPs of 36 μg/m L and Au-PLVs of 194μg/m L were safe to U87 cells.(2) The TEM results showed the presence of BSA-Au NPs in U87 cells after incubated for 6 h, and the LSCM results showed the presence of Au-PLVs in U87 cells after incubated for 45 min(3) Au NPs could reduce the colony survival rate of U87 cells(4) Through immunofluoresence assay, it was found that γ-H2 AX foci increased at 0.5 h and 2 h post-irradiation, both incubated with BSA-Au NPs and Au-PLVs.(5) Flow cytometry showed significantly increased the ratio of cell apoptosis at 48 h after radiation while no significant difference was found on the cell apoptosis at 0 h between cells treated with BSA-Au NPs and vehicle control.3 In vivo:(1) Through the text of ICP-AMS, the half-lives(t1/2) of BSA-Au NPs in nude mice is 0.328 h; and Au-PLVs is 0.245 h. Au NPs mainly accumulated in liver and spleen at 2 h and 24 h after intravenous administration.(2) The mice beraing tumor modals treated with Au NPs and irradiated by X-ray could been inhibited the growth of tumor efficiently. Bying the histological analysis, we could see the death of cells obviously.(3) The histological results showed that no significant impact was found on the main organ after the treatment of Au NPs, and there was no change at the weight of mouse during treatment.ConclusionOur study demonstrated that Au NPs have good radiotherapy sensitization Au NPs produce localized dose enhancement at the tumor because of their strong absorption and high efficiency in generating secondary electrons under ionizing radiation. Meanwhile, No obvious toxicity is observed in vitro and in vivo experiments. Our study showed BSA-Au NPs present great potentials in tumor therapy as the radiosensitizing agent.