Abstract
Purpose: This study investigated how the low‐energy electron energy spectrum is modified when a water nanoparticle is substituted by a gold nanoparticle irradiated by photon and electron beams. The distribution of low‐energy electrons was recently found playing an important role in the damage to DNA. Methods: Spherical gold nanoparticle with diameter of 100 nm was irradiated by electron (50 keV ∼ 4 MeV) and photon (50 kV ∼ 6 MV) beams in water. The cross‐sectional diameter of the beam was equal to the nanoparticle diameter with the beam central axis positioned at the center of the nanoparticle. Monte Carlo simulations were carried out using the Geant4 code to track all the secondary electrons from the gold nanoparticle in low‐energy range (< 100 eV). For comparison, Monte Carlo simulations were repeated with the gold nanoparticle replaced by water. Results: It is found that the yield of the low‐energy electron increases when gold nanoparticle is added to water. For 4 MeV electron beams, the number of low‐energy electron increases about 234% in the energy range < 100 eV, when the water nanoparticle is replaced by gold. In the energy range < 20 eV, the mean energy of the low‐energy electron is 12.8 eV in the presence of the gold nanoparticle. This is higher than that of the water nanoparticle (4.5 eV). With a larger number of low‐energy electron produced, the distribution of electron is more even when gold nanoparticle is present in water. Conclusion: From the results of increased yield of low‐energy electrons distributed more evenly in the low‐energy range in the presence of gold nanoparticle, it is concluded that gold nanoparticle can modify the low‐energy electron spectrum and production. This low‐energy electron spectral modification can enhance the DNA damage of cancer cell in radiotherapy. Natural Science Foundation of Anhui Province (11040606M132), Fundamental Research Funds for the Central Universities (Nos. 2012HGXJ0057, 2012HGXJ0062, 2012HGXJ0071, 2012HGBZ0190) and Seed Foundation of Hefei University of Technology (2012HGZY0007), P.R.China
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