BACKGROUND:Bismth-doped iron nanoparticles modified by hyaluronic acid (HA-BiIOPs) not only act as an effective MRI contrast agent, but also as a radiotherapy sensitizer.OBJECTIVE:To fabricate the HA-BiIOPs and to observe its effect to enhance the radiosensitivity of glioblastoma cells U87MG under X-ray radiation.METHODS:HA-BiIOPs were synthesized using hydrothermal polyol method. (1) Cytotoxicity: A cytotoxicity test was carried out on U87MG cells and rat vascular smooth muscle cells (VSMCs). Cell proliferation rate of two kinds of cells cultured with different concentrations of HA-BiIOPs (0, 12.5, 25, 50, 100, 200, 400 mg/L) at 24 hours after culture were determined by cell counting kit-8 assay. (2) Histological analysis: ICR mice were sacrificed after intravenous injection of HA-BiIOPs, and pathological changes of mouse visceral organs were observed under an optical microscope. (3) Cellular uptake: The HA-BiIOPs after entered into the cytoplasm were observed by Prussian blue staining. (4) Radiosensitization test: U87MG cells at Logarithmic growth stage were cultured in culture medium as control group, subjected to X-ray irradiation (0, 3, 6, 9 Gy) as radiotherapy group, cultured in HA-BiIOPs (0, 12.5, 25, 50, 100, 200 and 400 mg/L) as HA-BiIOPs group or subjected to HA-BiIOPs culture plus X-ray irradiation as combined therapy group. Then, the cell proliferation rate and cloning efficiency were measured at 24 hours after treatment.RESULTS AND CONCLUSION:(1) The HA-BiIOPs at different concentrations were non-cytotoxic for VSMC and U87MG cells. (2) After intravenous injection of HA-BiIOPs, there was no obvious toxicity to the mouse susceptible organs. (3) After 6 hours of culture, the HA-BiIOPs could be internalized by U87MG cells. (4) The proliferation rate of U87 cells was negatively correlated with the concentration of HA-BiIOPs (0-200 mg/L) and X-ray dose (0-9 Gy). Especialy, the combination of 6 Gy X-ray irradiation with 200 mg/L HA-BiIOPs dramatically decreased the cell viability that was decreased to (41±7)%. In the combined therapy group with 6 Gy X-ray and 100 mg/L HA-BiIOPs, the cells proliferation rate was significantly lower than that in the control and radiotherapy groups (P < 0.05). These results indicate that HA-BiIOPs have a radiosensitizative effect on glioblastoma cells U87MG.