Radiosensitization effects by bismuth oxide nanorods of different sizes in megavoltage external beam radiotherapy

BACKGROUND: Nanotechnology application has successfully reached numerous scientific breakthroughs including in radiotherapy. However, the clinical application of nanoparticles requires more diligent research primarily on the crucial parameters such as nanoparticle sizes. This study is aimed to investigate the influence of bismuth oxide nanorod (Bi(2)O(3)-NR) sizes on radiosensitization effects on MCF-7 and HeLa cell lines for megavoltage photon and electron beam radiotherapy. MATERIALS AND METHODS: MCF-7 and HeLa cells were treated with and without 0.5 μMol/L of Bi(2)O(3)-NR of varying sizes (60, 70, 80, and 90 nm). The samples, including the control groups, were exposed to different radiation doses (0–10 Gy), using photon (6 MV and 10 MV), and electron beam (6 MeV and 12 MeV) radiotherapy. Clonogenic assay was performed, and sensitization enhancement ratio (SER) was determined from linear quadratic based cell survival curves. RESULTS: The results depicted that 60 nm Bi(2)O(3)-NR yields the most excellent SER followed by 70 nm Bi(2)O(3)-NR. Meanwhile, the 80 and 90 nm Bi(2)O(3)-NR showed an insignificant difference between treated and untreated cell groups. This study also found that MCF-7 was subjected to more cell death compared to HeLa. CONCLUSION: 60 nm Bi(2)O(3)-NR was the optimal Bi(2)O(3)-NR size to induce radiosensitization effects for megavoltage external beam radiotherapy. The SER in photon beam radiotherapy marked the highest compared to electron beam radiotherapy due to decreased primary radiation energy from multiple radiation interaction and higher Compton scattering.