Department of Physics, College of Science, Imam Mohammad Ibn Saud Islamic University, Riyadh 11623, Saudi Arabia.
Department of Biomedical Technology, College of Applied Medical Sciences, King Saud University, Riyadh 11433, Saudi Arabia.
Molecules. 2022 Aug 19;27(16):5290. doi: 10.3390/molecules27165290.
Gold nanoparticles (GNPs) are used in proton therapy radio-sensitizers to help increase the dose of radiation to targeted tumors by the emission of secondary electrons. Thus, this study aimed to investigate the link between secondary electron yields produced from a nanoshell of GNPs and dose absorption according to the distance from the center of the nanoparticles by using a Monte Carlo model. Microscopic evaluation was performed by modeling the interactions of secondary electrons in a phase-space file (PSF), where the number of emitted electrons was calculated within a spherical GNP of 15 nm along with the absorbed dose near it. Then, the Geant4-DNA physics list was used to facilitate the tracking of low-energy electrons down to an energy below 50 eV in water. The results show a remarkable change in the number of secondary electrons, which can be compared at concentrations less than and greater than 5 mg/mL, with increased secondary electron production exhibited around NPs within a distance of 10-100 nm from the surface of all nanospheres. It was found that there was a steep dose enhancement drop-off up to a factor of dose enhancement factor (DFE) ≤ 1 within a short distance of 100 nm from the surface of the GNPs, which revealed that the dose enhancement existed locally at nanometer distances from the GNPs. Overall, our results indicate that the physical interactions of protons with GNP clusters should not be considered as being directly responsible for the radio-sensitization effect, but should be regarded as playing a major role in NP properties and concentrations, which has a subsequent impact on local dose enhancement.
金纳米颗粒（GNPs）被用于质子治疗放射增敏剂，通过发射次级电子来帮助增加靶向肿瘤的辐射剂量。因此，本研究旨在通过蒙特卡罗模型研究从 GNPs 纳米壳产生的次级电子产额与吸收剂量之间的关系，根据距离纳米颗粒中心的距离。通过在相空间文件 (PSF) 中对次级电子的相互作用进行建模来进行微观评估，其中在 15nm 的球形 GNPs 内计算了发射电子的数量，以及其附近的吸收剂量。然后，使用 Geant4-DNA 物理列表来帮助追踪低能电子，使其能量降低到 50eV 以下在水中。结果表明，次级电子的数量发生了显著变化，可以在浓度小于和大于 5mg/mL 时进行比较，在距离所有纳米球表面 10-100nm 范围内的 NPs 周围显示出次级电子产生的增加。结果发现，在距离 GNPs 表面 100nm 以内的短距离内，剂量增强因子（DFE）≤1 时，剂量增强急剧下降，这表明在纳米级距离处存在局部剂量增强。总体而言，我们的结果表明，质子与 GNPs 簇的物理相互作用不应被视为直接导致放射增敏效应的原因，而应被视为在 NP 性质和浓度方面发挥主要作用，这对局部剂量增强有后续影响。
