| Backgrounds and Objective:Malignant glioma is the most common primary intracranial tumor which has high incidence but low cure rate.Currently,surgery combined radiotherapy is the preferred treatment of glioma,while the widespread phenomenon of recurrence after radiotherapy have brought the patients great pain.More and more studies show that the key reason of glioma difficult to cuer but easy to recur lies in its high proliferation,invasion and radiation and chemo resistance which are unique to cancer stem cells.CD 133 positive cells,only a small number of glioma cells,show a variety of biological characteristics of brain glioma stem cells and play a key role in glioma occurrence,development,metastasis and recurrence.What's more,CD1133 is regarded as the most important marker of brain glioma stem cells.Naturally finding a novel therapeutic approaches focusing on killing CD 133 positive brain glioma stem cells is of certain academic significance and value.Gold nanorods as a special form of gold nanoparticles have a lot of features.Recent researches have shown that gold nanorods have superior effects in radio sensitization.Based on the above information,we will synthesize PEG-GNRs,then evaluate and compare it in vitro experiments with 6 MeV X-ray radiation on CD133+ BGSCs and brain glioma cells at the same mass concentration.We preliminary explore the radiosensitizing effect of PEG-GNRs through these experiments.These findings may hold great promise for brain glioma clinical trentments.Methods:The expression of CD 133 on the surface of U251 cells was assayed by flow cytometry.CD133+ cells were isolated by magnetic-activated cell sorting from U251 cell line.Proliferation,colony formation,differentiation,transwell invasion and tumor formation assay were performed to identify stem cell characteristics.And then,we used seed-mediated growth method to prepare gold nanorods(GNRs),and modified its surface chemical properties by means of non covalent bond with thiol polyethylene glycol(SH-PEG).GNRs and PEG-GNRs were characterized by transmission electron microscopy(TEM),zeta potential,ultraviolet-visible(UV-Vis)spectroscopy and Fourier transform infrared spectroscopy(FTIR).Inductively coupled plasma mass spectrometry(ICP-MS)was used to detect the concentration of GNRs and PEG-GNRs.U251 cells were treated by GNRs or PEG-GNRs and the cytotoxicity impact of the treatments was measured by CCK-8 assay.Cell viability and radiosensitizing effects of PEG-GNRs on CD133+ BGSCs and U251 cells were determined by CCK-8 assay,colony formation assay and apoptosis detection.Results:We successfully isolated CD 133+ cells from U251 cell lines by magnetic-activated cell sorting.The results suggested that CD133+ cells showed significant stem cell-like properties.We used seed-mediated growth method to prepare GNRs,the results showed that GNRs had good dispersity and uniform morphology:the average length were about 40 um and average width were about 11 um.After PEGylation,the cytotoxicity of GNRs decreased significantly.The combination of PEG-GNRs with radiation could decrease the viability of CD133+BGSCs and U251 cells in a does dependent manner,with the latter being stronger.Colony formation assay results showed that the enhancement ratios of the same mass concentration of PEG-GNRs were 1.10 and 1.34 respectively.Compared with single radiation,PEG-GNRs combined radiation can significantly increase the rate of CD133+ BGSCs cells apoptosis,the difference is statistically significant.While compared with U251 cells under the same conditions,the effect on promoting apoptosis of PEG-GNRs was weaker.Conclusion:PEG-GNRs can increase the radiation sensitivity of CD133+ BGSCs significantly,which may be due to its higher proapoptotic activity.While compared with U251 cells under the same conditions,the former being weaker,which may be related to cancer stem cell properties.Our results suggest the clinical potential of PEG-GNRs as a kind of effective radiosensitizer in improving the outcome of CD 13 3+ BGSCs radiotherapy. |
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