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  • br Fig TEM images of biosynthesized SeNPs A B

    2020-08-18


    Fig. 3. TEM images of biosynthesized SeNPs (A,B) and corresponding SAED pattern (C).
    Fig. 4. EDS pattern of synthesized selenium nanoparticles.
    Fig. 5. MTT cytotoxicity analysis: (A) In vitro cell viability of A549 cancer cells upon treated with SeNPs with and without X-ray irradiation; (B) In vitro cell viability of IMR-90 normal fibroblast cells after treated with SeNPs.
    apoptosis and Ursodeoxycholylglycine arresting mechanisms. From the earlier litera-ture reports it could be expected that the increased cell killing effect might be attributed to the X-ray irradiation that could generate reactive oxygen species (ROS), which is a crucial parameter in regulating the cancer cell progression in course of radio- and chemotherapeutic pro-cedures. In theory, photoelectric effect of radiosensitive objects is mostly dependent on its atomic radius, thus selenium (Z = 34) could be a capable candidate for causing photoelectric effect. In this experiment, cytotoxicity investigation is carried out for cancer as well as healthy cell lines. From Fig. 5b, SeNPs showed potent cytotoxicity effect in cancer cells whereas it showed relatively less toxic effect in normal healthy cells.
    Caspase-3 protein is treated as a crucial signaling module of the apoptosis cascade and plays a vital role in the cleavage of proteins thus leading to programmed cell destruction. The activity of caspase-3 de-termines the downstream activation of signaling pathways. Hence in this study, we have studied the caspase-3 activity of the SeNPs treat-ment with the lung cancer cells. As shown in Fig. 6, SeNPs have de-monstrated remarkably elevated caspase-3 activity in relation to that of the control. However, caspase-3 activity was even more elevated when
    Fig. 6. Caspase-3 activity of A549 cells upon treated with SeNPs with and without X-ray irradiation. 
    subjected to X-ray exposure than in the absence. Thus, these experi-mental results specified the involvement of SeNPs in the caspase-3 ac-tivation and downstream target that might considerably obstruct the cancer cell proliferation, thus suggesting apoptosis as a chief me-chanism of death.
    Live/dead analysis was carried out to investigate the cellular via-bility. The cells were treated with SeNPs in the presence and absence of X-ray exposure. From the Fig. 7, it was evident that the calcein presence in the live cell is denoted by the bright green colored fluorescence whereas ethidium homodimer-1 passes through the dead cells via da-maged surface membrane denoted by red color. The untreated cells presented major number of live cells as indicated by green fluorescence after 24 h treatment Ursodeoxycholylglycine while the SeNPs disclosed significant number of dead cells represented in a combination of red and green fluorescence. In particular, SeNPs followed by the treatment with X-ray exhibited predominant red fluorescence corresponding to dead cells. These find-ings apparently revealed the cytotoxic potential of SeNPs + X-ray combination in the lung cancer cells.
    4. Conclusion
    In conclusion, selenium nanoparticles (SeNPs) were biosynthesized and were characterized by means of UV–Vis absorption spectroscopic technique. A decrease in the absorption intensity was observed with the gradual increase in time, which referred the consumption of protein during the reduction of SeO32− to Se0. From XRD studies, the calculated average crystalline size of the synthesized selenium nanoparticles was found to be 88.89 nm which was in agreement with the TEM analysis while the SAED pattern has revealed hexagonal ring structure with diffraction ring pattern.MTT assay was carried out to investigate the radio-sensitizing effect of selenium nanoparticles under the X-ray in-fluence against cancer as well as healthy cell lines. SeNPs showed po-tent cytotoxicity effect in cancer cells whereas it showed relatively less toxic effect in normal healthy cells. However, caspase-3 activity was even more elevated when subjected to X-ray exposure than in the ab-sence. Also, the experimental findings specified the involvement of SeNPs in the caspase-3 activation and downstream target that might considerably obstruct the cancer cell proliferation, thus suggesting apoptosis as a chief mechanism of death. These results have evidently signified the cytotoxic potential of SeNPs with the combination of X-ray in the treatment of lung cancer cell lines.
    Fig. 7. Live/dead assay of cancer cells upon treated with SeNPs with and without X-ray irradiation (A). Fluorescence microscopic images of cancer cells corre-sponding to live and dead cells (B).
    Acknowledgements
    This work was supported by the Natural Science Foundation of China (81572881).